In this manuscript we report the crosslinking
of pre-existing macromolecules in solution through the use
of photoactive benzophenone chromophores. We show that
a bifunctional crosslinker composed of two benzophenone
chromophores as well as a single benzophenone chromophore
crosslink poly (butadiene) and poly (ethylene oxide)
in solution to form insoluble gels when irradiated with UV
light. The molecular weight between crosslinks of the photogenerated
gels was compared for the two crosslinkers, for an
equivalent amount of benzophenone chromophores in each
solution, by measuring the swelling ratio of the gels formed.
Gels formed from the bifunctional benzophenone crosslinker
were shown to contain more than twice as many
crosslinks compared to gels formed from the crosslinker
composed of a single benzophenone chromophore. EPR
measurements of a nitroxide derivative absorbed into the
gels further supported a higher crosslink density for the
gels formed from the bifunctional benzophenone crosslinker.
Synthesis and properties of PolyanilineAwad Albalwi
This document summarizes the synthesis and properties of polyaniline. Polyaniline was prepared through chemical and electrochemical polymerization in acidic medium. Different solvents, including DMF and m-cresol, were compared for their effect on polyaniline's conductivity. UV-vis spectroscopy and cyclic voltammetry were used to analyze the polymer films. The conductivity of polyaniline was influenced by acidity and the electronic structure of different solvents, which impacts the polymer chain conformation. Polyaniline in m-cresol had higher conductivity than in DMF due to stronger interactions between adjacent polarons.
This document summarizes a research article about a new dendronised polymer synthesized for use in bulk heterojunction solar cells. Key points:
- A poly[1,4-phenylenevinylene] polymer was synthesized with bulky first generation biphenyl dendrons attached to each monomer unit.
- The attachment of the dendrons did not disrupt the conjugation of the polymer backbone.
- Solar cells were made blending the polymer with PCBM acceptor. The best device had a power conversion efficiency of 0.44%, over 30 times higher than the only other report of a dendronised polymer solar cell.
Polyaniline (PANI) Metal Oxide Nano Composites as a Conducting MaterialRSIS International
The combination of conducting nanoparticles and conducting polymers is a new area of research. The conducting polymer nanocomposites have both advantages of low dimensional systems and organic conductors. With this nanofibre morphology, the dispersibility and processibility of polyanilines can be improved.
The aim of this literature is to provide a survey of previous findings of researchers related to metal oxide nanocomposite polyaniline. In this paper we reviewed the properties, methods of synthesis, and various applications.
This course provides an in-depth understanding of three-dimensional macromolecular structure and the relationship between the conformation of proteins and nucleic acids and their biological functions. Students will learn to visualize and analyze macromolecular structures using molecular graphics software and assess the structural basis of biological activity. The course covers topics related to multi-molecular assemblies, catalytic machines, and membrane proteins. Students will be assessed through a final exam and computer graphics exercises completed in a lab notebook.
Electrochemical Behavior of L-Tyrosine at Poly (Dicyclomine Hydrochloride) Fi...paperpublications3
Abstract: An electrochemical method for the determination of L-Tyrosine (LTY) using a dicyclomine hydrochloride (DICY) polymer film modified carbon paste electrode. The surface morphology of poly (DICY) modified carbon paste electrode was characterized by SEM. The modified electrode showed excellent electro catalytic activity towards the oxidation of LTY in 0.1 M phosphate buffer solution of pH 6.5. The effect of pH, concentration and scan rate were studied at the bare carbon paste electrode and poly (DICY) modified carbon paste electrode were investigated. Increase of LTY concentration shows linear increase in oxidation peak current. The linear relationship was obtained between the anodic peak current (Ipa) and concentration LTY in range 2×10-5 M to 1×10-3 M with correlation coefficient of 0.9984. The low detection limit (LOD) and low quantification limit (LOQ) of LTY were detected. The cyclic voltammetric studies indicated that the oxidation of LTY at the modified electrode surface was irreversible; adsorption controlled and undergoes a one electron transfer process at the poly (DICY) film modified carbon paste electrode. The modified electrode showed high sensitivity, detection limit, high reproducibility, easy preparation and regeneration of the electrode surface.
Synthesis and characterization of water-soluble free-base, zinc and copperAngela Mammana
We describe the synthesis and characterization of a series of water-soluble free-base, zinc, and copper
porphyrin–oligonucleotide (ODN) conjugates. A non-charged tetraarylporphyrin was directly attached
to the 50-position of thymine via a short amide linker. Such a linker should allow for rigid connection
to the adjacent nucleobases, thus increasing the sensitivity for monitoring conformational changes of
the ODNs by electronic circular dichroism due to capping effects or ligand binding. Two complementary
synthetic approaches have been used to incorporate porphyrin chromophores into the DNA. In the first
approach a porphyrin carboxylic acid is conjugated to 50-amino-ODN. In the second approach the phosphoramidite
of the porphyrin-amido-thymidine is coupled to 50-hydroxy-ODN using standard automated
phosphoramidite chemistry. In both cases a spontaneous metallation of the free-base porphyrin in porphyrin–
DNA conjugates was observed during the porphyrin–DNA conjugate cleavage from the solid support
and its consequent deprotection using concentrated aqueous ammonia. Zinc and copper porphyrin–
DNA conjugates were isolated by HPLC and characterized together with the anticipated free-base porphyrin–
DNA conjugate. Authentic zinc and copper porphyrin–DNA conjugates were intentionally prepared
from intentionally metallated porphyrins to compare their spectroscopic and HPLC characteristics with
isolated metallospecies and to confirm the spontaneous metallation.
Exploring Proteins and Proteomes. Stryer,CHAPTER 3 pptkhair ullah
Methods in Protein Chemistry
This chapter discusses several methods used to isolate, purify, detect, degrade, analyze, and synthesize proteins. It describes techniques such as centrifugation, solubility, dialysis, gel filtration, affinity chromatography, HPLC, electrophoresis, and mass spectrometry. It also covers determining a protein's amino acid sequence through methods like Edman degradation, solid phase synthesis, chemical and enzymatic cleavage, and the use of DNA sequencing. The goal of these methods is to obtain a protein's amino acid sequence and gain functional information about proteins and proteomes.
Synthesis and properties of PolyanilineAwad Albalwi
This document summarizes the synthesis and properties of polyaniline. Polyaniline was prepared through chemical and electrochemical polymerization in acidic medium. Different solvents, including DMF and m-cresol, were compared for their effect on polyaniline's conductivity. UV-vis spectroscopy and cyclic voltammetry were used to analyze the polymer films. The conductivity of polyaniline was influenced by acidity and the electronic structure of different solvents, which impacts the polymer chain conformation. Polyaniline in m-cresol had higher conductivity than in DMF due to stronger interactions between adjacent polarons.
This document summarizes a research article about a new dendronised polymer synthesized for use in bulk heterojunction solar cells. Key points:
- A poly[1,4-phenylenevinylene] polymer was synthesized with bulky first generation biphenyl dendrons attached to each monomer unit.
- The attachment of the dendrons did not disrupt the conjugation of the polymer backbone.
- Solar cells were made blending the polymer with PCBM acceptor. The best device had a power conversion efficiency of 0.44%, over 30 times higher than the only other report of a dendronised polymer solar cell.
Polyaniline (PANI) Metal Oxide Nano Composites as a Conducting MaterialRSIS International
The combination of conducting nanoparticles and conducting polymers is a new area of research. The conducting polymer nanocomposites have both advantages of low dimensional systems and organic conductors. With this nanofibre morphology, the dispersibility and processibility of polyanilines can be improved.
The aim of this literature is to provide a survey of previous findings of researchers related to metal oxide nanocomposite polyaniline. In this paper we reviewed the properties, methods of synthesis, and various applications.
This course provides an in-depth understanding of three-dimensional macromolecular structure and the relationship between the conformation of proteins and nucleic acids and their biological functions. Students will learn to visualize and analyze macromolecular structures using molecular graphics software and assess the structural basis of biological activity. The course covers topics related to multi-molecular assemblies, catalytic machines, and membrane proteins. Students will be assessed through a final exam and computer graphics exercises completed in a lab notebook.
Electrochemical Behavior of L-Tyrosine at Poly (Dicyclomine Hydrochloride) Fi...paperpublications3
Abstract: An electrochemical method for the determination of L-Tyrosine (LTY) using a dicyclomine hydrochloride (DICY) polymer film modified carbon paste electrode. The surface morphology of poly (DICY) modified carbon paste electrode was characterized by SEM. The modified electrode showed excellent electro catalytic activity towards the oxidation of LTY in 0.1 M phosphate buffer solution of pH 6.5. The effect of pH, concentration and scan rate were studied at the bare carbon paste electrode and poly (DICY) modified carbon paste electrode were investigated. Increase of LTY concentration shows linear increase in oxidation peak current. The linear relationship was obtained between the anodic peak current (Ipa) and concentration LTY in range 2×10-5 M to 1×10-3 M with correlation coefficient of 0.9984. The low detection limit (LOD) and low quantification limit (LOQ) of LTY were detected. The cyclic voltammetric studies indicated that the oxidation of LTY at the modified electrode surface was irreversible; adsorption controlled and undergoes a one electron transfer process at the poly (DICY) film modified carbon paste electrode. The modified electrode showed high sensitivity, detection limit, high reproducibility, easy preparation and regeneration of the electrode surface.
Synthesis and characterization of water-soluble free-base, zinc and copperAngela Mammana
We describe the synthesis and characterization of a series of water-soluble free-base, zinc, and copper
porphyrin–oligonucleotide (ODN) conjugates. A non-charged tetraarylporphyrin was directly attached
to the 50-position of thymine via a short amide linker. Such a linker should allow for rigid connection
to the adjacent nucleobases, thus increasing the sensitivity for monitoring conformational changes of
the ODNs by electronic circular dichroism due to capping effects or ligand binding. Two complementary
synthetic approaches have been used to incorporate porphyrin chromophores into the DNA. In the first
approach a porphyrin carboxylic acid is conjugated to 50-amino-ODN. In the second approach the phosphoramidite
of the porphyrin-amido-thymidine is coupled to 50-hydroxy-ODN using standard automated
phosphoramidite chemistry. In both cases a spontaneous metallation of the free-base porphyrin in porphyrin–
DNA conjugates was observed during the porphyrin–DNA conjugate cleavage from the solid support
and its consequent deprotection using concentrated aqueous ammonia. Zinc and copper porphyrin–
DNA conjugates were isolated by HPLC and characterized together with the anticipated free-base porphyrin–
DNA conjugate. Authentic zinc and copper porphyrin–DNA conjugates were intentionally prepared
from intentionally metallated porphyrins to compare their spectroscopic and HPLC characteristics with
isolated metallospecies and to confirm the spontaneous metallation.
Exploring Proteins and Proteomes. Stryer,CHAPTER 3 pptkhair ullah
Methods in Protein Chemistry
This chapter discusses several methods used to isolate, purify, detect, degrade, analyze, and synthesize proteins. It describes techniques such as centrifugation, solubility, dialysis, gel filtration, affinity chromatography, HPLC, electrophoresis, and mass spectrometry. It also covers determining a protein's amino acid sequence through methods like Edman degradation, solid phase synthesis, chemical and enzymatic cleavage, and the use of DNA sequencing. The goal of these methods is to obtain a protein's amino acid sequence and gain functional information about proteins and proteomes.
Chemical and electrochem method of synthesis of polyaniline and polythiophene...Mugilan Narayanasamy
This document summarizes chemical and electrochemical methods for synthesizing polyaniline and polythiophene. Polyaniline can exist in three oxidation states - leucoemeraldine, emeraldine, and pernigraniline. It can be synthesized chemically using an oxidative process with an acid and oxidizing agent like ammonium persulfate or potassium dichromate. Electrochemical synthesis grows a polyaniline film on an anode. Polythiophene is also synthesized chemically using oxidative polymerization with catalysts or electrochemically by applying a potential to drive polymerization. The McCullough and Rieke methods can produce regioregular polythiophene using nickel or palladium catalysts. Both polymers find applications in
Met human hemoglobin was successfully encapsulated in sol-gel derived nano particles using three different preparative methods. Absorption spectra showed the hemoglobin maintained functionality within the particles and was able to undergo changes in redox and ligation states. The encapsulated hemoglobin did not leak out of the particles. Particle sizes ranged from 200-400 nm depending on the preparation method. The results suggest this approach could create infusible, functional protein-containing nanoparticles for therapeutic use.
This document describes a study investigating a novel diblock copolymer electrolyte system for potential use in lithium-ion batteries. The system consists of dicarboximide functionalized oxanorbornyl diblock copolymers with oligo(ethylene oxide) sidechains of varying lengths. Atomic force microscopy was used to characterize the phase behavior and determine the phase diagram of these polymers in order to design nanostructured electrolyte supports. Preliminary experiments showed the homopolymer versions had competitive ionic conductivity to PEO without crystallization. The phase behavior was found to deviate substantially from theoretical models, believed to be due to conformational asymmetry between the blocks, with this effect increasing with longer sidechain lengths.
- The document studies using water as an alternative solvent to the commonly used acetonitrile for applying organic layers from diazonium salts.
- When using water, the diazonium salt solution had to be replaced every couple days to maintain a consistent concentration, as the salt decomposed over time, turning the solution orange.
- Preliminary results found that layers could be applied using water as a solvent, but it may lack control over completeness of the layer compared to acetonitrile.
Protein purification techniques can be categorized into those based on molecular size, solubility, and electric charge. Size-based techniques include dialysis, ultrafiltration, and size-exclusion chromatography which separate proteins based on their ability to pass through semi-permeable membranes or porous beads. Solubility-based techniques include isoelectric precipitation and salting out which alter a protein's solubility by adjusting pH or salt concentration. Charge-based techniques such as ion-exchange and electrophoresis separate proteins using their net electric charge in an applied electric field or ion-exchange column.
Electropolymerization of Polyaniline in the Presence of FerricyanideFarhadAkrami1
This document summarizes research on electropolymerizing polyaniline in the presence of ferricyanide. Key findings include:
1) Electropolymerization with ferricyanide leads to its incorporation into the resulting polyaniline film and increases the deposition rate compared to polyaniline alone.
2) Simultaneous cyclic voltammetry and quartz crystal microbalance measurements show an "inverted" mass transport behavior, suggesting a cation-exchange mechanism.
3) The polyaniline-ferricyanide film displays different electrochemical and mass transport behavior than films made with FeCl3 or RuCl3, which do not enhance polymerization.
This document describes Michael Ludden's synthesis and characterization of various molybdenum complexes. Three complexes were synthesized - [CpMo(CO)3Me], [CpMo(CO)3Et], and [CpMo(CO)2(COMe)(PPh3)]. They were characterized using NMR and IR spectroscopy. The results confirmed the structures of the complexes and showed how changing ligands affects properties. Kinetic measurements of migratory insertion reactions will be taken using these complexes to understand reaction rate dependence on factors like solvent, temperature and ligand type.
1. Immunoprecipitation is a technique used to isolate a protein of interest along with any interacting proteins from a mixture. It involves using an antibody against the target protein to form an immune complex, which is then isolated using a secondary antibody or protein A/G.
2. Immunogold labeling localizes proteins in cells and tissues using antibodies tagged with gold particles and visualized with electron microscopy. It was used in one study to quantify serotonin receptor subtypes in post-mortem brain samples from suicide victims versus controls.
3. Western blotting separates proteins by gel electrophoresis then transfers them to a membrane where antibodies are used to detect specific proteins. It allows visualization and quantification of proteins.
This document discusses supramolecular polymers, which are polymeric arrays brought together by non-covalent interactions like hydrogen bonding, metal coordination, and π-π stacking. It provides examples of hydrogen bonding between molecules like PEG and methyl isocytosine, and metal coordination involving ligands. Supramolecular polymers can be synthesized through reactions like one producing a quadruple hydrogen bond supramolecular polymer from PEG and MIC, with characteristics analyzed using techniques like FTIR, UV-Vis, NMR, and DSC.
Study of electrical properties of Polythiophene and its compositesIOSR Journals
Conducting polymers are known to have significant electrical properties which can be improved by strong oxidizing power of oxidizing agents like V2O5. In the current study oxidative polymerization of the thiophene monomers was done to obtain Polythiophene for converting it into its composites with V2O5 to study their improved electrical nature. The electrical properties of pure Polythiophene, pure V2O5, PTh- V2O5 composite 1:2 (thiophene: V2O5) and PTh- V2O5 composite 2:1(thiophene: V2O5) were studied by carrying out current voltage measurements. It can be stated that the increased concentration of V2O5 is responsible for the increased current flow through the polymer matrix. The study is explained on the basis of fact that oxidizing power leads to removal of higher number of charge carriers from the backbone thereby causing increases in current flow. Such conducting polymers have wide range of applications in the field of Metal ions detectors, molecular electronics, conductive adhesive, electrical displays, electromagnetic shields, chemical, biochemical and thermal sensors, rechargeable batteries, solid electrolytes, optical computers and ion exchange membrane
Rotaxanes are supramolecular assemblies consisting of a macrocyclic molecule threaded onto a linear molecule capped with bulky stoppers. They can be synthesized through template-directed methods like clipping, threading, and snapping. Switchable rotaxanes have applications in logic gates and memory due to their ability to shuttle between binding stations. Rotaxanes can also be used to enhance or reduce reactivity, act as molecular muscles, and self-assemble into structures that can slowly release dye.
Overview of the pigment Chlorophyll, its sources, types, structure, photoreceptors, benefits, stability, degradation, preservation during food processing and technologies associated with it.
This document summarizes research on using amine-rich nitrogen-doped carbon nanodots (NCNDs) as a co-reactant platform for electrochemiluminescence (ECL). The NCNDs were found to enhance the ECL signal of ruthenium tris(bipyridine) through their primary and tertiary amino groups acting as co-reactants in the ECL process. Methylated NCNDs, with tertiary amino groups, showed an even higher ECL signal than unmodified NCNDs. Additionally, a covalently linked hybrid of NCNDs and ruthenium tris(bipyridine) exhibited self-enhanced ECL, with the NCND
Fullerene Functionalized Thiophene Derivative as an Acceptor Material for Org...CrimsonPublishersRDMS
Fullerene Functionalized Thiophene Derivative as an Acceptor Material for Organic Photovoltaics by Ranjith Kottokkaran* in Research & Development in Material Science
This document provides guidance on protein purification methods. It discusses lysing cells to release the target protein, protecting the protein from degradation during purification, tracking the protein using activity assays and purification tables, initial gentle fractionation using ammonium sulfate precipitation, chromatographic separation methods like ion exchange and affinity chromatography, and final polishing steps like additional chromatography or ultrafiltration. The overall goal is to leverage the target protein's unique properties to separate it from contaminants through a series of purification techniques.
The document summarizes a student research project investigating the design of short peptide amphiphiles that can bind transition metal ions. The student synthesized a peptide called C16-AHLHL3K3 and used various characterization techniques. Results showed the peptide formed beta-pleated sheet fibers under certain conditions and was able to bind transition metals like cobalt. This demonstrates the potential for short peptides to have transition metal binding sites and possibly enzymatic capabilities.
This document discusses the influence of various factors on counterion condensation in aqueous solutions of sodium polystyrenesulfonate polyelectrolyte. Electrical conductivity measurements were used to analyze the interactions between the polyion and counterions. The extent of counterion condensation was found to be affected by the polyelectrolyte concentration and molecular weight, added electrolyte concentration, and temperature. The results provide insight into how polyelectrolyte molecular weight influences counterion condensation behavior in the presence of added electrolytes.
Maskless Nanopattering and Formation of Nanocorrals and Switches for Haloalka...ioneec
This document summarizes research on the self-assembly and stabilization of nanopatterns formed by haloalkane molecules on silicon surfaces. In 3 sentences:
1) The researchers show that propyl bromide molecules self-assemble into circular patterns on a Si(111)-7x7 surface at 50K, and these labile patterns can be stabilized through a "maskless imprinting" process using localized chemical reactions induced by photons or electrons, forming stable circular patterns of atomic bromine.
2) They also find that at room temperature, longer-chain octyl chloride and bromide molecules adsorb horizontally and spontaneously self-assemble into stable "nanocorrals" surrounding surface defects ("type II") or into
This document describes a study of the effects of solvent and molecular weight on the fluorescence emission of MEH-PPV. MEH-PPV samples with three different molecular weights were dissolved in two solvents, chloroform and toluene, at various concentrations. Fluorescence spectra were recorded for the solutions and films cast from the solutions. The films cast from chloroform solutions exhibited lower crystallinity than those from toluene solutions. A red shift in the fluorescence spectra was observed at higher concentrations, which can be explained by Kasha's rule regarding chromophore orientation. The conformations observed in solution are partially retained in the solid films. Annealing films eliminates stressed conformations and leads to sharper fluorescence spectra.
Visible Spectrophotometric Determination of Gemigliptin Using Charge Transfer...Ratnakaram Venkata Nadh
A visible spectrophotometric method was developed and validated for the determination of gemigliptin present in bulk drug and tablet formulation. It involves an indirect method of charge transfer complex formation in presence of NBS, metol and suphanilic acid. Gemigliptin was subjected to oxidation with excess amount of oxidant (NBS) and the unconsumed NBS oxidizes metol to give p-N-methylbenzoquinone monoamine (PNMM) which in turn forms a charge transfer complex with sulphanilic acid. Then validated the above developed method as per the current ICH guidelines. An excellent correlation coefficient (> 0.999) was found for the obtained regression equation
(y = –0.0302x + 0.928) in the range of 2.0–30.0 μg mL-1. The method was found to be simple and rapid because it does not involve any solvent extraction. The recovery levels of the drug were in the range 99.92 – 100.08.
Spontaneous Generation and Long-range Patterning of Chiral Polymeric Surface ...Gregory Carroll
1) A chiral polymer called poly(n-hexyl isocyanate) forms ordered toroidal structures when drop-cast from solution onto various surfaces.
2) The toroids are arranged in a highly ordered pattern over large areas exceeding 100 microns.
3) The formation of these toroidal structures upon solvent evaporation is an unusual phenomenon that is not fully understood but may involve the chiral and rigid nature of the polymer chains interacting as the solvent dries.
Photochemical Micropatterning of Carbohydrates on a SurfaceGregory Carroll
In this report, we demonstrate a versatile method for the immobilization and patterning of unmodified carbohydrates
onto glass substrates. The method employs a novel self-assembled monolayer to present photoactive phthalimide
chromophores at the air-monolayer interface. Upon exposure to UV radiation, the phthalimide end-groups graft to
surface-adsorbed carbohydrates, presumably by a hydrogen abstraction mechanism followed by radical recombination
to form a covalent bond. Immobilized carbohydrate thin films are evidenced by fluorescence, ellipsometry and contactangle
measurements. Surface micropatterns of mono-, oligo-, and polysaccharides are generated by exposure through
a contact photomask and are visualized by condensing water onto the surface. The efficiency of covalent coupling
is dependent on the thermodynamic state of the surface. The amount of surface-grafted carbohydrate is enhanced when
carbohydrate surface interactions are increased by the incorporation of amine-terminated molecules into the monolayer.
Glass substrates modified with mixed monolayers of this nature are used to construct carbohydrate microarrays by
spotting the carbohydrates with a robot and subsequently illuminating them with UV light to covalently link the
carbohydrates. Surface-immobilized polysaccharides display well-defined antigenic determinants for antibody recognition.
We demonstrate, therefore, that this novel technology combines the ability to create carbohydrate microarrays using
the current state-of-the-art technology of robotic microspotting and the ability to control the shape of immobilized
carbohydrate patterns with a spatial resolution defined by the UV wavelength and a shape defined by a photomask.
Chemical and electrochem method of synthesis of polyaniline and polythiophene...Mugilan Narayanasamy
This document summarizes chemical and electrochemical methods for synthesizing polyaniline and polythiophene. Polyaniline can exist in three oxidation states - leucoemeraldine, emeraldine, and pernigraniline. It can be synthesized chemically using an oxidative process with an acid and oxidizing agent like ammonium persulfate or potassium dichromate. Electrochemical synthesis grows a polyaniline film on an anode. Polythiophene is also synthesized chemically using oxidative polymerization with catalysts or electrochemically by applying a potential to drive polymerization. The McCullough and Rieke methods can produce regioregular polythiophene using nickel or palladium catalysts. Both polymers find applications in
Met human hemoglobin was successfully encapsulated in sol-gel derived nano particles using three different preparative methods. Absorption spectra showed the hemoglobin maintained functionality within the particles and was able to undergo changes in redox and ligation states. The encapsulated hemoglobin did not leak out of the particles. Particle sizes ranged from 200-400 nm depending on the preparation method. The results suggest this approach could create infusible, functional protein-containing nanoparticles for therapeutic use.
This document describes a study investigating a novel diblock copolymer electrolyte system for potential use in lithium-ion batteries. The system consists of dicarboximide functionalized oxanorbornyl diblock copolymers with oligo(ethylene oxide) sidechains of varying lengths. Atomic force microscopy was used to characterize the phase behavior and determine the phase diagram of these polymers in order to design nanostructured electrolyte supports. Preliminary experiments showed the homopolymer versions had competitive ionic conductivity to PEO without crystallization. The phase behavior was found to deviate substantially from theoretical models, believed to be due to conformational asymmetry between the blocks, with this effect increasing with longer sidechain lengths.
- The document studies using water as an alternative solvent to the commonly used acetonitrile for applying organic layers from diazonium salts.
- When using water, the diazonium salt solution had to be replaced every couple days to maintain a consistent concentration, as the salt decomposed over time, turning the solution orange.
- Preliminary results found that layers could be applied using water as a solvent, but it may lack control over completeness of the layer compared to acetonitrile.
Protein purification techniques can be categorized into those based on molecular size, solubility, and electric charge. Size-based techniques include dialysis, ultrafiltration, and size-exclusion chromatography which separate proteins based on their ability to pass through semi-permeable membranes or porous beads. Solubility-based techniques include isoelectric precipitation and salting out which alter a protein's solubility by adjusting pH or salt concentration. Charge-based techniques such as ion-exchange and electrophoresis separate proteins using their net electric charge in an applied electric field or ion-exchange column.
Electropolymerization of Polyaniline in the Presence of FerricyanideFarhadAkrami1
This document summarizes research on electropolymerizing polyaniline in the presence of ferricyanide. Key findings include:
1) Electropolymerization with ferricyanide leads to its incorporation into the resulting polyaniline film and increases the deposition rate compared to polyaniline alone.
2) Simultaneous cyclic voltammetry and quartz crystal microbalance measurements show an "inverted" mass transport behavior, suggesting a cation-exchange mechanism.
3) The polyaniline-ferricyanide film displays different electrochemical and mass transport behavior than films made with FeCl3 or RuCl3, which do not enhance polymerization.
This document describes Michael Ludden's synthesis and characterization of various molybdenum complexes. Three complexes were synthesized - [CpMo(CO)3Me], [CpMo(CO)3Et], and [CpMo(CO)2(COMe)(PPh3)]. They were characterized using NMR and IR spectroscopy. The results confirmed the structures of the complexes and showed how changing ligands affects properties. Kinetic measurements of migratory insertion reactions will be taken using these complexes to understand reaction rate dependence on factors like solvent, temperature and ligand type.
1. Immunoprecipitation is a technique used to isolate a protein of interest along with any interacting proteins from a mixture. It involves using an antibody against the target protein to form an immune complex, which is then isolated using a secondary antibody or protein A/G.
2. Immunogold labeling localizes proteins in cells and tissues using antibodies tagged with gold particles and visualized with electron microscopy. It was used in one study to quantify serotonin receptor subtypes in post-mortem brain samples from suicide victims versus controls.
3. Western blotting separates proteins by gel electrophoresis then transfers them to a membrane where antibodies are used to detect specific proteins. It allows visualization and quantification of proteins.
This document discusses supramolecular polymers, which are polymeric arrays brought together by non-covalent interactions like hydrogen bonding, metal coordination, and π-π stacking. It provides examples of hydrogen bonding between molecules like PEG and methyl isocytosine, and metal coordination involving ligands. Supramolecular polymers can be synthesized through reactions like one producing a quadruple hydrogen bond supramolecular polymer from PEG and MIC, with characteristics analyzed using techniques like FTIR, UV-Vis, NMR, and DSC.
Study of electrical properties of Polythiophene and its compositesIOSR Journals
Conducting polymers are known to have significant electrical properties which can be improved by strong oxidizing power of oxidizing agents like V2O5. In the current study oxidative polymerization of the thiophene monomers was done to obtain Polythiophene for converting it into its composites with V2O5 to study their improved electrical nature. The electrical properties of pure Polythiophene, pure V2O5, PTh- V2O5 composite 1:2 (thiophene: V2O5) and PTh- V2O5 composite 2:1(thiophene: V2O5) were studied by carrying out current voltage measurements. It can be stated that the increased concentration of V2O5 is responsible for the increased current flow through the polymer matrix. The study is explained on the basis of fact that oxidizing power leads to removal of higher number of charge carriers from the backbone thereby causing increases in current flow. Such conducting polymers have wide range of applications in the field of Metal ions detectors, molecular electronics, conductive adhesive, electrical displays, electromagnetic shields, chemical, biochemical and thermal sensors, rechargeable batteries, solid electrolytes, optical computers and ion exchange membrane
Rotaxanes are supramolecular assemblies consisting of a macrocyclic molecule threaded onto a linear molecule capped with bulky stoppers. They can be synthesized through template-directed methods like clipping, threading, and snapping. Switchable rotaxanes have applications in logic gates and memory due to their ability to shuttle between binding stations. Rotaxanes can also be used to enhance or reduce reactivity, act as molecular muscles, and self-assemble into structures that can slowly release dye.
Overview of the pigment Chlorophyll, its sources, types, structure, photoreceptors, benefits, stability, degradation, preservation during food processing and technologies associated with it.
This document summarizes research on using amine-rich nitrogen-doped carbon nanodots (NCNDs) as a co-reactant platform for electrochemiluminescence (ECL). The NCNDs were found to enhance the ECL signal of ruthenium tris(bipyridine) through their primary and tertiary amino groups acting as co-reactants in the ECL process. Methylated NCNDs, with tertiary amino groups, showed an even higher ECL signal than unmodified NCNDs. Additionally, a covalently linked hybrid of NCNDs and ruthenium tris(bipyridine) exhibited self-enhanced ECL, with the NCND
Fullerene Functionalized Thiophene Derivative as an Acceptor Material for Org...CrimsonPublishersRDMS
Fullerene Functionalized Thiophene Derivative as an Acceptor Material for Organic Photovoltaics by Ranjith Kottokkaran* in Research & Development in Material Science
This document provides guidance on protein purification methods. It discusses lysing cells to release the target protein, protecting the protein from degradation during purification, tracking the protein using activity assays and purification tables, initial gentle fractionation using ammonium sulfate precipitation, chromatographic separation methods like ion exchange and affinity chromatography, and final polishing steps like additional chromatography or ultrafiltration. The overall goal is to leverage the target protein's unique properties to separate it from contaminants through a series of purification techniques.
The document summarizes a student research project investigating the design of short peptide amphiphiles that can bind transition metal ions. The student synthesized a peptide called C16-AHLHL3K3 and used various characterization techniques. Results showed the peptide formed beta-pleated sheet fibers under certain conditions and was able to bind transition metals like cobalt. This demonstrates the potential for short peptides to have transition metal binding sites and possibly enzymatic capabilities.
This document discusses the influence of various factors on counterion condensation in aqueous solutions of sodium polystyrenesulfonate polyelectrolyte. Electrical conductivity measurements were used to analyze the interactions between the polyion and counterions. The extent of counterion condensation was found to be affected by the polyelectrolyte concentration and molecular weight, added electrolyte concentration, and temperature. The results provide insight into how polyelectrolyte molecular weight influences counterion condensation behavior in the presence of added electrolytes.
Maskless Nanopattering and Formation of Nanocorrals and Switches for Haloalka...ioneec
This document summarizes research on the self-assembly and stabilization of nanopatterns formed by haloalkane molecules on silicon surfaces. In 3 sentences:
1) The researchers show that propyl bromide molecules self-assemble into circular patterns on a Si(111)-7x7 surface at 50K, and these labile patterns can be stabilized through a "maskless imprinting" process using localized chemical reactions induced by photons or electrons, forming stable circular patterns of atomic bromine.
2) They also find that at room temperature, longer-chain octyl chloride and bromide molecules adsorb horizontally and spontaneously self-assemble into stable "nanocorrals" surrounding surface defects ("type II") or into
This document describes a study of the effects of solvent and molecular weight on the fluorescence emission of MEH-PPV. MEH-PPV samples with three different molecular weights were dissolved in two solvents, chloroform and toluene, at various concentrations. Fluorescence spectra were recorded for the solutions and films cast from the solutions. The films cast from chloroform solutions exhibited lower crystallinity than those from toluene solutions. A red shift in the fluorescence spectra was observed at higher concentrations, which can be explained by Kasha's rule regarding chromophore orientation. The conformations observed in solution are partially retained in the solid films. Annealing films eliminates stressed conformations and leads to sharper fluorescence spectra.
Visible Spectrophotometric Determination of Gemigliptin Using Charge Transfer...Ratnakaram Venkata Nadh
A visible spectrophotometric method was developed and validated for the determination of gemigliptin present in bulk drug and tablet formulation. It involves an indirect method of charge transfer complex formation in presence of NBS, metol and suphanilic acid. Gemigliptin was subjected to oxidation with excess amount of oxidant (NBS) and the unconsumed NBS oxidizes metol to give p-N-methylbenzoquinone monoamine (PNMM) which in turn forms a charge transfer complex with sulphanilic acid. Then validated the above developed method as per the current ICH guidelines. An excellent correlation coefficient (> 0.999) was found for the obtained regression equation
(y = –0.0302x + 0.928) in the range of 2.0–30.0 μg mL-1. The method was found to be simple and rapid because it does not involve any solvent extraction. The recovery levels of the drug were in the range 99.92 – 100.08.
Spontaneous Generation and Long-range Patterning of Chiral Polymeric Surface ...Gregory Carroll
1) A chiral polymer called poly(n-hexyl isocyanate) forms ordered toroidal structures when drop-cast from solution onto various surfaces.
2) The toroids are arranged in a highly ordered pattern over large areas exceeding 100 microns.
3) The formation of these toroidal structures upon solvent evaporation is an unusual phenomenon that is not fully understood but may involve the chiral and rigid nature of the polymer chains interacting as the solvent dries.
Photochemical Micropatterning of Carbohydrates on a SurfaceGregory Carroll
In this report, we demonstrate a versatile method for the immobilization and patterning of unmodified carbohydrates
onto glass substrates. The method employs a novel self-assembled monolayer to present photoactive phthalimide
chromophores at the air-monolayer interface. Upon exposure to UV radiation, the phthalimide end-groups graft to
surface-adsorbed carbohydrates, presumably by a hydrogen abstraction mechanism followed by radical recombination
to form a covalent bond. Immobilized carbohydrate thin films are evidenced by fluorescence, ellipsometry and contactangle
measurements. Surface micropatterns of mono-, oligo-, and polysaccharides are generated by exposure through
a contact photomask and are visualized by condensing water onto the surface. The efficiency of covalent coupling
is dependent on the thermodynamic state of the surface. The amount of surface-grafted carbohydrate is enhanced when
carbohydrate surface interactions are increased by the incorporation of amine-terminated molecules into the monolayer.
Glass substrates modified with mixed monolayers of this nature are used to construct carbohydrate microarrays by
spotting the carbohydrates with a robot and subsequently illuminating them with UV light to covalently link the
carbohydrates. Surface-immobilized polysaccharides display well-defined antigenic determinants for antibody recognition.
We demonstrate, therefore, that this novel technology combines the ability to create carbohydrate microarrays using
the current state-of-the-art technology of robotic microspotting and the ability to control the shape of immobilized
carbohydrate patterns with a spatial resolution defined by the UV wavelength and a shape defined by a photomask.
The interesting structural, electronic, and optical properties
of DNA provide fascinating opportunities for developing nanoscale smart
materials by integrating DNA with opto-electronic components. In this
article we demonstrate the electrostatic binding of an amine-terminated
dithienylethene (DET) molecular switch to double-stranded synthetic
polynucleotides. The DET switch can undergo photochemical ring-closure
and opening reactions. Circular dichroism (CD) and UVvis spectroscopy
show that both the open, 1o, and the closed, 1c, forms of the switch bind
to DNA. Upon addition of DNA to a solution of 1o or 1c, the UVvis
spectrum displays a hypochromic effect, indicative of an interaction between the switch and the DNA. The chirality of the DNA
double-helix is transmitted to the switching unit which displays a well-defined CD signal upon supramolecular complexation to the
DNA. Additionally, the CD signal of the DNA attenuates, demonstrating that both components of the complex mutually influence
each other's structure; the DNA induces chirality in the switch, and the switch modifies the structure of the DNA. Modulation of the
chiroptical properties of the complex is achieved by photochemically switching the DET between its ring open and closed isomers.
A pH dependence study of the binding shows that when the pH is increased the switches lose their binding ability, indicating that
electrostatic interactions between protonated amines and the negatively charged phosphate backbone are the dominant driving
force for binding to the DNA. A comparison of poly(deoxyguanylic-deoxycytidylic) acid [poly(dGdC)2] polynucleotides with
poly(deoxyadenylic-deoxythymidylic) acid [poly(dAdT)2] shows distinct differences in the CD spectra of the complexes. Original Source: http://pubs.acs.org/doi/abs/10.1021/jp205893y
Controlled rotary motion of light-driven molecular motors assembled onGregory Carroll
Using circular dichroism (CD) spectroscopy, we show that light-driven rotary molecular motors based
on overcrowded alkenes can function in a self-assembled monolayer on semi-transparent gold films.
Photoactive Additives for Crosslinking Thin Polymer Films: Inhibition of Dewe...Gregory Carroll
In this report, we describe a versatile photochemical method for cross-linking polymer films and demonstrate that
this method can be used to inhibit thin polymer films from dewetting. A bifunctional photoactive molecule featuring
two benzophenone chromophores capable of abstracting hydrogen atoms from various donors, including C-H groups,
is mixed into PS films. Upon exposure to UV light, the bis-benzophenone molecule cross-links the chains presumably
by hydrogen abstraction followed by radical recombination. Photoinduced cross-linking is characterized by infrared
spectroscopy and gel permeation chromatography. Optical and atomic force microscopy images show that
photocrosslinked polystyrene (PS) thin films resist dewetting when heated above the glass transition temperature or
exposed to solvent vapor. PS films are inhibited from dewetting on both solid and liquid substrates. The effectiveness
of the method to inhibit dewetting is studied as a function of the ratio of cross-linker to macromolecule, duration of
exposure to UV light, film thickness, the driving force for dewetting, and the thermodynamic nature of the substrate.
Adhesion of Photon-driven Molecular Motors to Surfaces via 1,3-dipolar Cycloa...Gregory Carroll
We report the attachment of altitudinal light-driven molecular motors to surfaces using 1,3-
dipolar cycloaddition reactions. Molecular motors were designed containing azide or alkyne groups for attachment
to alkyne- or azide-modified surfaces. Surface attachment was characterized by UVvis, IR, XPS, and ellipsometry
measurements. Surface-bound motors were found to undergo photochemical and thermal isomerizations
consistent with unidirectional rotation in solution. Confinement at a surface was found to reduce the rate of the
thermal isomerization process. The rate of thermal isomerization was also dependent on the surface coverage of
the motors. In solution, changes in the UVvis signal that accompany thermal isomerization can be fit with a
single monoexponential decay. In contrast, thermal isomerization of the surface-bound motors does not follow a
single monoexponential decay and was found to fit a biexponential decay. Both one- and two-legged motors were
attached to surfaces. The kinetics of thermal isomerization was not affected by the valency of attachment,
indicating that the changes in kinetics from solution to surface systems are related to interactions between the
surface-bound motors.
This document discusses immobilization of biomolecules on biomaterial surfaces. It begins by explaining that biomaterials must have suitable bulk and surface properties to function in biological environments. Common approaches involve fabricating materials with adequate bulk properties, then modifying the surface to enhance biocompatibility. The document then discusses various biomolecules that can be immobilized on surfaces like proteins, peptides, polysaccharides and describes techniques for covalent and non-covalent immobilization. Specific examples of immobilizing collagen, RGD peptide, hyaluronic acid and other biomolecules on scaffolds are provided to support tissue engineering applications.
Synthesis and characterication of water soluble conjugated polymer brush for ...Hnakey Lora
This document discusses the synthesis and characterization of water-soluble conjugated polymer brushes for sensor applications. It describes how conjugated polyelectrolytes (CPEs) can change their optical properties in response to environmental perturbations, making them useful for sensing biomolecules. However, linear CPEs have limitations like low water solubility. The document then discusses how attaching highly charged polymer side chains overcomes these limitations by increasing water solubility and quantum yield. Several new CPE brushes were successfully synthesized and shown to have properties desirable for sensing, like optical stability in complex media.
Interaction of Components in Molecular Optoelectronics for the Next Generati...Scientific Review SR
The interaction of molecular optoelectronic components on the molecular scale were studied where
the solvent shell indicating the influence of the medium was found to be surprisingly small. The transport of
energy as resonant energy transfer covers distances of about 5 nm and was shown not to proceed by a simple to
dipole dipole interaction with typical restrictions, but by a more complex mechanism. Furthermore, a novel -type of
far-reaching interactions of electronically excited structures until macroscopic dimensions were fond and may be
applied for addressing molecular structures by conventional electronics
This document summarizes research on using boron-doped carbon nanotubes (B-CNTs) as a catalyst for oxygen dissociation in proton exchange membrane fuel cells (PEMFCs). Density functional theory (DFT) calculations were performed to model oxygen adsorption and dissociation on a (5,5) single-walled carbon nanotube (SWCNT) with one hexagon replaced by B3C3 (B3SWCNT). The nudged elastic band (NEB) method was used to calculate minimum energy reaction paths and activation barriers. The results show an average activation barrier of 1.01 eV for oxygen dissociation on the B3SWCNT, with the most favorable path having a barrier
Unusual Electronic Properties of Cellulose Nanocrystals Conjugated to Cobalt ...Pawan Kumar
Octacarboxylated cobalt phthalocyanine (CoPc) was covalently conjugated to cellulose nanocrystals (CNCs) by employing an esterification protocol. Solid-state NMR, X-ray photoelectron spectroscopy (XPS), Raman, and infrared spectra were used to verify and study the nature of covalent attachment responsible for the immobilization of CoPc on the CNC surface. The covalent attachment was investigated from a theoretical simulation perspective using dispersion-corrected density functional theory (DFT) calculations, which verified the stable bond formation between CNC and CoPc. CoPc is an organic semiconductor with a high exciton binding energy, and CNCs are known to be insulating. Yet, Kelvin probe force microscopy (KPFM) indicated charge carrier generation and long-lived charge separation in the CNC–CoPc conjugate compared to pristine CoPc under visible light illumination. Such behavior is more typical of a semiconductor nanocomposite. The CNC–CoPc conjugate exhibited superior performance in the visible-light-driven surface photocatalytic reduction of 4-nitrobenzenethiol (4-NBT) to p,p′-dimercaptoazobenzene (DMAB) and photodegradation of rhodamine B.
A molecular-dynamics-investigation-of-the-stability-of-a-charged-electroactiv...Darren Martin Leith
1) A molecular dynamics simulation investigates the stability of a charged electroactive polymer monolayer consisting of an amphiphilic polythiophene on a sodium chloride solution.
2) When the monolayer is chemically reduced, negative charges are conferred on the thiophene rings. This leads to a loss of planarity and buckling of the monolayer, eventually causing it to rupture. It also attracts excess sodium ions to the interface.
3) At low levels of reduction, interface sodium ions are more mobile than sodium ions in the NaCl solution, responding to electric fields by jumping between sites with an energy barrier of 0.33 eV. The instability of the charged polymer membrane is discussed using Gou
The document discusses a study that measured the electrical conductivity of solutions of sodium polystyrenesulphonate in mixed solvent systems of 2-ethoxyethanol and water at varying concentrations, temperatures, and solvent compositions. The results showed that equivalent conductivity increased slightly with decreasing polymer concentration. Equivalent conductivity also increased with increasing temperature and relative permittivity of the solvent system. However, the experimentally determined conductivities did not fully match what was predicted by Manning's counterion condensation theory. Reasons for this discrepancy are discussed.
S Ramakrishnan discusses condensation polymerization, also known as step-growth polymerization. He describes how polymers form through reactions between small molecules that link together, like LEGO blocks fitting together. An example given is the reaction between a dicarboxylic acid and a diol to form a polyester polymer. Ramakrishnan defines important terms like functionality, fractional conversion, and degree of polymerization. He derives the Carothers equation, which relates the fractional conversion (extent of reaction) to the average length of the polymer chains formed (degree of polymerization).
This document summarizes a study that developed a new hybrid electrocatalyst for oxygen evolution reaction (OER) by anchoring cobalt oxide (Co3O4) nanoparticles onto titanium carbide (Ti3C2) MXene nanosheets. The Co3O4/MXene hybrid (denoted CM) was synthesized using a solvothermal method. Characterization showed uniform distribution of small Co3O4 nanoparticles on MXene nanosheets. Electrochemical tests found the CM catalyst achieved overpotential of 300 mV at 10 mA/cm2 for OER, which was lower than Co3O4 or MXene alone. The enhanced performance was attributed to strong interactions and charge transfer between
Scott Shaw conducted research investigating strong coupling of β-carotene in microcavities. He was successful in achieving the strong coupling regime, obtaining a Rabi splitting of ~2.1 eV, over twice as large as the next highest. Degradation experiments showed β-carotene films deteriorated quickly when exposed to light and water, but less so under nitrogen. While a large splitting was achieved, the system was likely not emissive due to aggregation-induced quenching. The research demonstrated strong coupling of β-carotene can be achieved under specified fabrication and storage conditions.
This document contains lecture notes for an advanced photochemistry course taught by Dr. Fateh Eltaboni at the University of Benghazi. The 3-credit, 3-hour course covers fundamental photochemical principles, energy transfer processes, photochemical reactions and their quantum yields, photochemistry in nature, and special topics. The notes provide definitions of key photochemistry concepts, discuss light absorption and emission by molecules, and outline reaction types for carbonyl compounds under light, among other topics.
Short Lifetimes of Light Emitting PolymersJeffrey Gold
This document provides a literature survey on the short lifetimes of light emitting polymers. It begins with background on polymers and electroluminescence. Key points discussed include the history of light emitting polymers starting in 1990, methods of synthesizing polymers and fabricating devices, and the physics of electroluminescence in polymers. The document focuses on the mechanisms responsible for the short lifetimes of these materials, addressing issues such as photo-oxidation, singlet oxygen, carbonyl groups, oxygen migration, recrystallization, and problems related to electrodes. Understanding degradation mechanisms is important to improve polymer device lifetimes.
The document summarizes research on a photoswitchable DNA complex consisting of a dithienylethene (DET) molecular switch bound electrostatically to double-stranded DNA. The DET switch can undergo reversible photochemical ring-opening and closing, existing in either the open (1o) or closed (1c) form. Both 1o and 1c bind to DNA through electrostatic interactions between their protonated amine groups and the negatively charged phosphate backbone of DNA. This results in an induced circular dichroism signal from the DET, demonstrating it has taken on the chirality of the bound DNA helix. The complex can be photochemically switched between states by irradiating with UV or visible light
The document summarizes recent research on new electro-optic properties of polysiloxane liquid crystal polymers. A series of polysiloxane-based side-chain liquid crystal polymers were prepared with systematic variation in spacer length between the mesogenic units and the polymer backbone. Electro-optic measurements showed that threshold voltage decreased with increasing spacer length. This was attributed to changes in intrinsic curvature elasticity rather than orientational order. Threshold voltage also decreased with increasing temperature and orientational order parameter. The results were consistent with existing models of curvature deformation in liquid crystals and provided insight into the effects of constraints from coupling mesogenic units to the polymer backbone.
This document summarizes recent developments in side chain liquid crystal polymers, focusing on polysiloxane based polymers. It discusses how a series of these polymers were prepared with systematic variation in the spacer length between the mesogenic units and the polymer backbone. Electro-optic measurements found that increasing the spacer length lowered the threshold voltage for molecular reorientation. A simple model indicates this is due to changes in intrinsic curvature elasticity rather than orientational order as the constraints from the polymer backbone are reduced with longer spacers.
Organic solar cells the exciting interplay of excitons and nano-morphologyvvgk-thalluri
1) The document summarizes organic solar cells, which use a bulk heterojunction of a conjugated polymer donor and fullerene acceptor. When light is absorbed, excitons are formed that must dissociate at the donor-acceptor interface into free charges.
2) The bulk heterojunction morphology, consisting of an interpenetrating network of the donor and acceptor materials, allows more excitons to dissociate since the interface is throughout the volume. This leads to higher efficiencies than simple bilayer cells.
3) Efficiencies of over 6% have been achieved but further work is needed to improve stability and lower costs for organic solar cells to become commercially viable. Optimization of
Catalyst Advancements in Microbial Fuel Cells: Pioneering Renewable Energy So...piyushpandey409164
Microbial Fuel Cells (MFCs) harness the power of microorganisms to convert organic matter into electricity while treating wastewater. By utilizing various biomass sources like wood, food waste, and sewage sludge, MFCs offer a sustainable solution for renewable energy production without competing with food sources. Originally conceptualized in 1911 by Potter, MFC technology has evolved, utilizing catalysts like Escherichia coli and Saccharomyces cerevisiae, and electrodes such as platinum. Over time, advancements have led to the elimination of artificial mediators, with bacteria directly transferring electrons to electrodes. MFCs stand as a promising avenue for clean energy generation, aligning with the imperative to mitigate climate change and reduce reliance on fossil fuels.
This document summarizes research on the photoelectrocatalytic degradation of Remazol Black B (RBB) dye using nanostructured tungsten oxide (WO3) film electrodes. Key findings include:
1) WO3 film electrodes were found to be better photoelectrocatalysts for degrading RBB dye than titanium dioxide (TiO2) electrodes or molybdenum oxide (MoO3) electrodes with similar surface roughness.
2) Kinetic measurements showed the degradation of RBB on WO3 followed a generalized Langmuir-Hinshelwood model with an overall rate constant of 1.1 × 10−9 mol cm−2s−1.
3
Use of stoichiometric amounts of a chiral source. The usual suspects will be discussed, including borane reagents (mostly pinene derivatives) and the Brown allylation.
This document summarizes a study on the effect of different solvent systems on poly(lactic acid) (PLA) nanofibres produced through electrospinning. PLA solutions were prepared using various single solvents and mixed solvent systems. Of the single solvents tested, only acetone produced continuous nanofibres, while the others resulted in beads. The addition of acetone to other solvents in a 50/50 mixture improved fibre production. Solutions of acetone/dimethylformamide and acetone/dimethylacetamide produced smooth, bead-free nanofibres with the narrowest diameter distribution. The mixed solvent systems had lower viscosity and surface tension but higher conductivity than single solvents, enabling better fibre formation
Similar to Photogeneration of Gelatinous Networks from Pre-existing Polymers (20)
Maruthi Prithivirajan, Head of ASEAN & IN Solution Architecture, Neo4j
Get an inside look at the latest Neo4j innovations that enable relationship-driven intelligence at scale. Learn more about the newest cloud integrations and product enhancements that make Neo4j an essential choice for developers building apps with interconnected data and generative AI.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
Full-RAG: A modern architecture for hyper-personalizationZilliz
Mike Del Balso, CEO & Co-Founder at Tecton, presents "Full RAG," a novel approach to AI recommendation systems, aiming to push beyond the limitations of traditional models through a deep integration of contextual insights and real-time data, leveraging the Retrieval-Augmented Generation architecture. This talk will outline Full RAG's potential to significantly enhance personalization, address engineering challenges such as data management and model training, and introduce data enrichment with reranking as a key solution. Attendees will gain crucial insights into the importance of hyperpersonalization in AI, the capabilities of Full RAG for advanced personalization, and strategies for managing complex data integrations for deploying cutting-edge AI solutions.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
“An Outlook of the Ongoing and Future Relationship between Blockchain Technologies and Process-aware Information Systems.” Invited talk at the joint workshop on Blockchain for Information Systems (BC4IS) and Blockchain for Trusted Data Sharing (B4TDS), co-located with with the 36th International Conference on Advanced Information Systems Engineering (CAiSE), 3 June 2024, Limassol, Cyprus.
Unlock the Future of Search with MongoDB Atlas_ Vector Search Unleashed.pdfMalak Abu Hammad
Discover how MongoDB Atlas and vector search technology can revolutionize your application's search capabilities. This comprehensive presentation covers:
* What is Vector Search?
* Importance and benefits of vector search
* Practical use cases across various industries
* Step-by-step implementation guide
* Live demos with code snippets
* Enhancing LLM capabilities with vector search
* Best practices and optimization strategies
Perfect for developers, AI enthusiasts, and tech leaders. Learn how to leverage MongoDB Atlas to deliver highly relevant, context-aware search results, transforming your data retrieval process. Stay ahead in tech innovation and maximize the potential of your applications.
#MongoDB #VectorSearch #AI #SemanticSearch #TechInnovation #DataScience #LLM #MachineLearning #SearchTechnology
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
Pushing the limits of ePRTC: 100ns holdover for 100 daysAdtran
At WSTS 2024, Alon Stern explored the topic of parametric holdover and explained how recent research findings can be implemented in real-world PNT networks to achieve 100 nanoseconds of accuracy for up to 100 days.
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
Unlocking Productivity: Leveraging the Potential of Copilot in Microsoft 365, a presentation by Christoforos Vlachos, Senior Solutions Manager – Modern Workplace, Uni Systems
Building RAG with self-deployed Milvus vector database and Snowpark Container...Zilliz
This talk will give hands-on advice on building RAG applications with an open-source Milvus database deployed as a docker container. We will also introduce the integration of Milvus with Snowpark Container Services.
Enchancing adoption of Open Source Libraries. A case study on Albumentations.AIVladimir Iglovikov, Ph.D.
Presented by Vladimir Iglovikov:
- https://www.linkedin.com/in/iglovikov/
- https://x.com/viglovikov
- https://www.instagram.com/ternaus/
This presentation delves into the journey of Albumentations.ai, a highly successful open-source library for data augmentation.
Created out of a necessity for superior performance in Kaggle competitions, Albumentations has grown to become a widely used tool among data scientists and machine learning practitioners.
This case study covers various aspects, including:
People: The contributors and community that have supported Albumentations.
Metrics: The success indicators such as downloads, daily active users, GitHub stars, and financial contributions.
Challenges: The hurdles in monetizing open-source projects and measuring user engagement.
Development Practices: Best practices for creating, maintaining, and scaling open-source libraries, including code hygiene, CI/CD, and fast iteration.
Community Building: Strategies for making adoption easy, iterating quickly, and fostering a vibrant, engaged community.
Marketing: Both online and offline marketing tactics, focusing on real, impactful interactions and collaborations.
Mental Health: Maintaining balance and not feeling pressured by user demands.
Key insights include the importance of automation, making the adoption process seamless, and leveraging offline interactions for marketing. The presentation also emphasizes the need for continuous small improvements and building a friendly, inclusive community that contributes to the project's growth.
Vladimir Iglovikov brings his extensive experience as a Kaggle Grandmaster, ex-Staff ML Engineer at Lyft, sharing valuable lessons and practical advice for anyone looking to enhance the adoption of their open-source projects.
Explore more about Albumentations and join the community at:
GitHub: https://github.com/albumentations-team/albumentations
Website: https://albumentations.ai/
LinkedIn: https://www.linkedin.com/company/100504475
Twitter: https://x.com/albumentations
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?Speck&Tech
ABSTRACT: A prima vista, un mattoncino Lego e la backdoor XZ potrebbero avere in comune il fatto di essere entrambi blocchi di costruzione, o dipendenze di progetti creativi e software. La realtà è che un mattoncino Lego e il caso della backdoor XZ hanno molto di più di tutto ciò in comune.
Partecipate alla presentazione per immergervi in una storia di interoperabilità, standard e formati aperti, per poi discutere del ruolo importante che i contributori hanno in una comunità open source sostenibile.
BIO: Sostenitrice del software libero e dei formati standard e aperti. È stata un membro attivo dei progetti Fedora e openSUSE e ha co-fondato l'Associazione LibreItalia dove è stata coinvolta in diversi eventi, migrazioni e formazione relativi a LibreOffice. In precedenza ha lavorato a migrazioni e corsi di formazione su LibreOffice per diverse amministrazioni pubbliche e privati. Da gennaio 2020 lavora in SUSE come Software Release Engineer per Uyuni e SUSE Manager e quando non segue la sua passione per i computer e per Geeko coltiva la sua curiosità per l'astronomia (da cui deriva il suo nickname deneb_alpha).
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/building-and-scaling-ai-applications-with-the-nx-ai-manager-a-presentation-from-network-optix/
Robin van Emden, Senior Director of Data Science at Network Optix, presents the “Building and Scaling AI Applications with the Nx AI Manager,” tutorial at the May 2024 Embedded Vision Summit.
In this presentation, van Emden covers the basics of scaling edge AI solutions using the Nx tool kit. He emphasizes the process of developing AI models and deploying them globally. He also showcases the conversion of AI models and the creation of effective edge AI pipelines, with a focus on pre-processing, model conversion, selecting the appropriate inference engine for the target hardware and post-processing.
van Emden shows how Nx can simplify the developer’s life and facilitate a rapid transition from concept to production-ready applications.He provides valuable insights into developing scalable and efficient edge AI solutions, with a strong focus on practical implementation.
Removing Uninteresting Bytes in Software FuzzingAftab Hussain
Imagine a world where software fuzzing, the process of mutating bytes in test seeds to uncover hidden and erroneous program behaviors, becomes faster and more effective. A lot depends on the initial seeds, which can significantly dictate the trajectory of a fuzzing campaign, particularly in terms of how long it takes to uncover interesting behaviour in your code. We introduce DIAR, a technique designed to speedup fuzzing campaigns by pinpointing and eliminating those uninteresting bytes in the seeds. Picture this: instead of wasting valuable resources on meaningless mutations in large, bloated seeds, DIAR removes the unnecessary bytes, streamlining the entire process.
In this work, we equipped AFL, a popular fuzzer, with DIAR and examined two critical Linux libraries -- Libxml's xmllint, a tool for parsing xml documents, and Binutil's readelf, an essential debugging and security analysis command-line tool used to display detailed information about ELF (Executable and Linkable Format). Our preliminary results show that AFL+DIAR does not only discover new paths more quickly but also achieves higher coverage overall. This work thus showcases how starting with lean and optimized seeds can lead to faster, more comprehensive fuzzing campaigns -- and DIAR helps you find such seeds.
- These are slides of the talk given at IEEE International Conference on Software Testing Verification and Validation Workshop, ICSTW 2022.
Goodbye Windows 11: Make Way for Nitrux Linux 3.5.0!SOFTTECHHUB
As the digital landscape continually evolves, operating systems play a critical role in shaping user experiences and productivity. The launch of Nitrux Linux 3.5.0 marks a significant milestone, offering a robust alternative to traditional systems such as Windows 11. This article delves into the essence of Nitrux Linux 3.5.0, exploring its unique features, advantages, and how it stands as a compelling choice for both casual users and tech enthusiasts.
Photogeneration of Gelatinous Networks from Pre-existing Polymers
1. Photogeneration of Gelatinous Networks from
Pre-Existing Polymers
Gregory T. Carroll,1
L. Devon Triplett,1
Alberto Moscatelli,1
Jeffrey T. Koberstein,2
Nicholas J. Turro1,2
1
Department of Chemistry, Columbia University, MC 3157, New York, New York 10027
2
Department of Chemical Engineering, Columbia University, New York, New York 10027
Received 14 November 2010; accepted 23 December 2010
DOI 10.1002/app.34133
Published online 20 April 2011 in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: In this manuscript we report the crosslinking
of pre-existing macromolecules in solution through the use
of photoactive benzophenone chromophores. We show that
a bifunctional crosslinker composed of two benzophenone
chromophores as well as a single benzophenone chromo-
phore crosslink poly (butadiene) and poly (ethylene oxide)
in solution to form insoluble gels when irradiated with UV
light. The molecular weight between crosslinks of the photo-
generated gels was compared for the two crosslinkers, for an
equivalent amount of benzophenone chromophores in each
solution, by measuring the swelling ratio of the gels formed.
Gels formed from the bifunctional benzophenone cross-
linker were shown to contain more than twice as many
crosslinks compared to gels formed from the crosslinker
composed of a single benzophenone chromophore. EPR
measurements of a nitroxide derivative absorbed into the
gels further supported a higher crosslink density for the
gels formed from the bifunctional benzophenone crosslinker.
VC 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 168–174, 2011
Key words: crosslink; gels; benzophenone; photochemistry;
swelling
INTRODUCTION
The physical properties of polymer solutions can be
modified by crosslinking the chains to form an
extended network (Fig. 1). Such networks offer
increased durability1
compared to their uncros-
slinked counter-parts and are pertinent in a variety
of current and future applications including
absorbent2,3
and elastic4
materials, photoresists for
micro- and nanofabrication,5,6
membranes,7,8
tissue
engineering,9
and controlled drug release.10
The
properties of crosslinked polymers depend on the
crosslink density. As more crosslinks are formed the
viscosity of the sample will increase. At the gel point
the system undergoes a sharp transition at which
the network becomes macroscopic and acts like an
elastic solid rather than a viscous liquid.11
Such a
network is said to be infinite with every chain form-
ing a bond with at least two other chains. When
such a gel is placed in a good solvent, rather than
dissolve, the gel will absorb the liquid and swell.
Although a gel has mechanical properties associated
with solids such as a nonzero sheer modulus, a large
fraction of the gel can consist of solvent.12
Some gels
can absorb an amount of solvent that is hundreds of
times the mass of the dry gel.2,3
A variety of photochemical methods have been
reported for crosslinking polymers.6
Many methods
rely on crosslinkable pendant groups in the chain.
Polymers containing groups susceptible to polymer-
ization via a photo-initiated process provide suitable
pendant groups for photo-crosslinking. For example,
acetylene containing polymers have been crosslinked
by irradiation in the presence of tungsten hexacar-
bonyl.13
Other methods require only a photo-active
functional group. Polymers containing various C¼¼C
groups can be dimerized via a photo-induced cyclo-
addition. Specific examples include polymers con-
taining pendant cinnamate14
and anthracene15,16
groups. Irradiation of polymers containing phenolic
OAH groups results in the cleavage of the OAH
bond.17
The resulting phenoxyl radicals can dimerize
to form a crosslink. The reaction is facilitated in the
presence of oxygen, which can abstract a hydrogen
atom from the phenolic OAH group. Poly (styrene)
(PS) similarly undergoes crosslinking by direct exci-
tation of the phenyl ring.18,19
Energy transfer results
in the cleavage of a benzylic CAH bond. The result-
ing radicals undergo secondary processes that result
in crosslinks. Polymers containing photo-active
pendant groups that can generate species that react
with CAH and other common functionalities upon
absorption of a photon have also been used to cross-
link polymers. Pendant benzophenone20
and azide21
Correspondence to: N. J. Turro (njt3@columbia.edu).
Contract grant sponsor: National Science Foundation;
contract grant numbers: 0717518, DMR 0703054
Journal of Applied Polymer Science, Vol. 122, 168–174 (2011)
VC 2011 Wiley Periodicals, Inc.
2. moieties have been used to effect crosslinks in this
way. Incorporating chromophores that react with
CAH and other functionalities into bifunctional mol-
ecules provides a more general protocol for cross-
linking, allowing networks to be formed from pre-
existing polymers that do not contain photo-active
groups.22,23
Crosslinks are generated by recombina-
tion of macroradicals or recombination of both sides
of the bi-functional molecule with a polymer. Mono-
functional reactive compounds that can abstract only
one hydrogen atom to form radicals are also capable
of generating crosslinks in polymers by forming
macroradicals that recombine to form covalent
bonds.24,25
Even more general, irradiating polymers
with deep UV can cause crosslinking by chain scis-
sion followed by recombination of the resulting radi-
cals.6
This can potentially damage functional groups
in the chain, compromising the functional properties
of the resulting crosslinked network.
The ability to crosslink polymers without prior
chemical derivatization or synthesis of a polymer
with pendant photo-active groups is of interest
because it avoids the often-laborious and expensive
task of synthetic chemistry. We previously demon-
strated a photochemical method for crosslinking and
patterning pre-existing poly (styrene) (PS) films
through the use of bisbenzophenone additives.23
In
this report we utilize the methodology for crosslink-
ing polymers in solution to form macroscopic net-
works. We provide evidence that crosslinking results
from the photo-generation of radical species. We
compare the swelling properties of networks formed
by both bis- and mono-functional benzophenone.
METHODS
bis-BP was synthesized according to a previously
reported procedure.23
After chromatography the product
was further purified by recystallization from methanol.
Photochemical crosslinking in solution
Both PBD and PEO gels were prepared in solutions
that were deoxygenated by bubbling with argon for
10 min followed by irradiation with a Rayonet pho-
tochemical reactor containing bulbs that emit at 350
nm. In a typical procedure for preparing PBD gels
3.5 lmol (0.01744 g) of bis-BP were added to a solu-
tion of 27.4 lmol (0.01312 g) of PBD in 2 mL of ben-
zene. The sample was irradiated for 2 h. In a typical
procedure for preparing PEO gels 29.2 lmol (0.01397
g) of bis-BP was added to a solution of 0.097 lmol
(0.0194 g) of PEO (200,000 K) (Acros) in 2 mL of ace-
tonitrile. PEO gels made with BP (Acros) were simi-
larly prepared using a 2Â molar amount of BP to
keep the amount of chromophores equal between
the two samples. Samples were irradiated for 5 h
and 40 min.
Swelling measurements
Photo-generated gels were soaked in good solvent
for 3 days, changing the solvent each day before per-
forming swelling measurements. Gels were then
dried at room temperature in a vacuum oven until
an unchanging dry weight was obtained. Gels were
then soaked in a given solvent for 1 day. Gels were
removed from the solvent, lightly tapped with Tef-
lon tape to remove excess solvent at the surface and
weighed. Gels were then placed back in the vacuum
oven to repeat the measurements.
Instrumental measurements
EPR measurements were performed using a Bruker
EMX EPR spectrometer. Photo-generated PEO gels
($ 4 h of irradiation with set-up described above)
were soaked overnight in a solution of 33.4 lmol
(0.00568 g) of 4-Oxo-Tempo in 6.7 mL of acetonitrile.
The nitroxide solution was removed, the samples
were each rinsed twice with DI water, and EPR
spectra were taken of the two gels.
RESULTS AND DISCUSSION
Benzophenone chromophores26
are known to
undergo hydrogen abstraction reactions with hydro-
gen atom donors such as CAH groups, and thus are
Figure 1 Schematic of the transformation of a group of polymer chains (left) into a single gel of crosslinked macromole-
cules (right).
PHOTOGENERATION OF GELATINOUS NETWORKS 169
Journal of Applied Polymer Science DOI 10.1002/app
3. capable of crosslinking a wide variety of different
polymer types as long as they possess CAH bonds.
We examined the solution-phase crosslinking poten-
tial of both bis- (bis-BP) and mono-functional benzo-
phenone (BP), both of which are shown in Figure 2.
Benzophenone is well suited for our studies for a va-
riety of reasons. It is generally not reactive when
kept in the dark. It can be excited at wavelengths
above 350 nm, which is generally less destructive
than shorter wavelength UV. Its photophysical and
photochemical properties have been well studied,
including its propensity for hydrogen abstraction.26
BP has previously been shown to crosslink poly-
mers.24
The proposed mechanism involves the
formation of macroradicals by hydrogen abstraction
followed by recombination. We reasoned that incor-
porating multiple benzophenone chromophores into
one molecule should increase the chances for cross-
linking a variety of polymer types with different
CAH bond strengths and in different environments
because this allows for more than one plausible
mechanism for crosslinks to form as shown in
Figure 3. Irradiation is expected to produce an
excited n–p* state that intersystem crosses to the tri-
plet.26
One of several deactivation pathways
includes hydrogen abstraction of a nearby CAH
group on a polymer chain. Hydrogen abstraction
will form radicals that can recombine to form cova-
lent bonds. Two potential recombination pathways
can result in crosslinks. First, radical centers on the
polymer chains can recombine with each other. This
requires that the photo-generated macroradicals are
located sufficiently close to each other. Note that
this pathway may be limited in environments where
chain motion is hindered. Second, the inclusion of
two benzophenone chromophores supplies an addi-
tional crosslinking pathway that circumvents the
need to have two macroradical centers in close
proximity. Recombination of two benzophenone
ketyl radicals at the ends of a single molecule of bis-
BP with macroradicals results in crosslinks without
the need for two interacting polymer radicals. The
main possible side reactions include recombination
of the ketyl radicals to produce pinnacol derivatives
that may or may not act as extended crosslink
bridges and disproportionation products.
Figure 2 Structure of photo-active crosslinkers.
Figure 3 Two pathways are proposed for crosslinking of polymers by bis-BP. In the first, radicals created on polymer
chains by hydrogen abstraction can recombine to form crosslinks. In the second, after bis-BP abstracts hydrogen atoms
from polymer chains, recombination between a polymer radical and a benzophenone ketyl radical result in a covalent
bond. When this happens on both benzophenone chromophores, a crosslink will result.
170 CARROLL ET AL.
Journal of Applied Polymer Science DOI 10.1002/app
4. To test the versatility of the photo-crosslinking
reaction in solution we selected poly (butadiene)
(PBD) and poly (ethylene oxide) (PEO), two poly-
mers containing different physical and chemical
properties. For example, PEO is hydrophilic and
expected to result in a hydrogel when crosslinked,
whereas, PBD is hydrophobic and is not expected
to absorb an appreciable amount of water. Regard-
less of the physical and chemical properties, irradi-
ation of both polymers in the presence of BP or
bis-BP resulted in the precipitation of insoluble
material from deoxygenated solutions. Gels photo-
generated from bis-BP are displayed in Figure 4.
Irradiation of deoxygenated polymer solutions
without crosslinker did not result in the formation
of gels.
A variety of methods have been used to charac-
terize crosslinked networks including small angle
neutron scattering,27
pulsed-field gradient,28,29
and
solid-state NMR,30,31
IR,32
AFM,33,34
and rheology35
measurements. Swelling measurements provide a
convenient technique for characterizing crosslinks in
a variety of polymers that allows for the crosslink
density to be calculated based on the ratio of the
volume of the swollen gel to the dry gel.11,36,37
We
compared the crosslink density of PEO gels photo-
generated using BP and bis-BP by analyzing the
swelling ratios of the two gels using both toluene
and acetonitrile as swelling solvents. These solvents
were selected because their solubility parameters,
18.2 and 24.3 (MPa)1/2
, are slightly above and below
that of PEO, 20.2 6 2 (MPa)1/2
.38
In addition, the
volatility of these solvents was low enough such that
a stable weight of swollen gel could be obtained.
The PEO gels clearly swell in comparison with the
dry gel as shown in Figure 5. From the swelling
Figure 4 Photo-generated PBD and PEO gels using bis-BP. Gels were also obtained when BP was used as the
crosslinker.
PHOTOGENERATION OF GELATINOUS NETWORKS 171
Journal of Applied Polymer Science DOI 10.1002/app
5. ratio the molecular weight between crosslinks, Mc,
can be calculated from the following equation:
1=ðmMcÞ ¼ ðlnð1 À m2Þ þ m2 þ v1m2
2Þ=ð/ðm
1=3
2 À m2=2ÞÞ
(1)
where m is the specific volume of the polymer, m2 is
the volume fraction of polymer, v is the Flory inter-
action parameter and / is the molar volume of
solvent. m2 can be calculated from the swelling ratio,
q, according to eq. (2):
q ¼ V=Vo ¼ 1=m2 (2)
where V is the volume of the wet gel and Vo is the
volume of the dry gel. Mc values and the crosslink
density, mx, for BP and bis-BP PEO gels are shown in
Table I. The crosslink density was calculated from
eq. (3):
mx ¼ 1=ðmMcÞ (3)
A higher crosslink density was calculated for the
bis-BP PEO gels regardless of the swelling solvent.
We conclude therefore that the bis-BP gel is more
heavily crosslinked than the BP gel. This is expected
since bis-BP has more than one mode of forming
crosslinks. When a BP ketyl radical recombines with a
polymer radical, a potential polymer–polymer cross-
link is lost. However, when a bis-BP ketyl radical
recombines with a polymer radical a polymer–poly-
mer crosslink can still be formed if the second chro-
mophore recombines either with a polymer radical or
another bis-BP ketyl radical attached to a polymer.
We also examined the crosslink density using EPR
spectroscopy. The line shape of an EPR spectrum
relates to the rotational correlation time of the para-
magnetic species.39
Hindered molecules rotate more
slowly, making it more difficult to align its magnetic
moment with the applied magnetic field. Such a
spectrum will typically have unequal peak heights
and broaden in comparison to a sample in an envi-
ronment where rotation is less hindered. Nitroxide
molecules are common EPR probes because
they contain stable radicals. We reasoned that if the
Figure 5 Dry and swollen PEO gels photo-generated by irradiation of acetonitrile solutions containing PEO and BP or
bis-BP. Gels were soaked in acetonitrile for 12 h. Similar results were obtained using toluene.
TABLE I
Comparison of the Molecular Weight Between
Crosslinks (Mc) and Cross-Link Density (mx) for PEO
Gels Photo-Crosslinked by BP and bis-BP
Crosslinker
Acetonitrile Toluene
Mc mx Mc mx
BP 8900 6 1500 150 6 20 7000 6 4000 220 6 90
bis-BP 3600 6 800 380 6 80 1300 6 200 1000 6 150
172 CARROLL ET AL.
Journal of Applied Polymer Science DOI 10.1002/app
6. bis-BP gels are more heavily crosslinked than the BP
gel, nitroxides absorbed into the gel should give a
signal indicative of slower rotation. We incubated
BP and bis-BP PEO gels overnight in acetonitrile sol-
utions containing 4-Oxo-Tempo. After removing the
nitroxide supernatant we took EPR spectra of the
gels (Fig. 6). Each gel showed the characteristic three
line EPR spectrum exhibited by nitroxide radicals,
indicating that nitroxide absorbed into the gel. The
gel photo-generated from BP [Fig. 6(a)] shows a
much more intense signal, indicating that nitroxide
more easily penetrated this gel. The spectrum of the
gel photo-generated from bis-BP [Fig. 6(b)] shows an
attenuated signal for the peak at the highest field,
which is a sign of a longer rotational correlation
time. The peaks for the BP gel are broader; however
this can be a result of oxygen penetrating the net-
work. We attribute these results to a higher crosslink
density in the bis-BP gels since a higher crosslink
density is expected to make the gel less permeable
and to inhibit the rotational diffusion of molecules
that are absorbed into the gel. In conjunction with
the swelling studies described above, we conclude
that bis-BP is a more efficient crosslinker than BP.
CONCLUSIONS
We have shown that both BP and bis-BP are capable
of crosslinking polymers in solution. In comparison
with BP, analysis of the swelling ratios of photo-
generated PEO gels as well as EPR measurements of
absorbed nitroxide probes shows that bis-BP gels are
more highly crosslinked. Although we have focused
on crosslinking traditional macromolecules, we
expect that the methodology is suitable for stabili-
zing and networking a variety of systems including
emerging materials based on self-assembly and
supramolecular chemistry.40,41
References
1. Kim, T.; Chan, K. C.; Crooks, R. M. J Am Chem Soc 1997, 119,
189.
2. Buchholz, F. L.; Peppas, N. A. Superabsorbent Polymers; ACS
Symposium Series 573; American Chemical Society: Washing-
ton, DC, 1994.
3. Raju, M. P.; Raju, K. M. J Appl Polym Sci 2001, 80, 2635.
4. Flory, P. J. Chem Rev 1944, 35, 51.
5. Madou, M. J. Fundamentals of Microfabrication, 2nd ed.; CRC
Press: New York, 2002.
6. Schnabel, W. Polymers and Light Fundamentals and Technical
Applications; Wiley-VCH: Weinheim, 2007.
7. Dai, W. S.; Barbari, T. A. J Membr Sci 1999, 156, 67.
8. Vankelecom Ivo, F. J. Chem Rev 2002, 102, 3779.
9. Lee, K. Y.; Mooney, D. J. Chem Rev 2001, 101, 1869.
10. Uhrich, K. E.; Cannizzaro, S. M.; Langer, R. S.; Shakesheff, K.
M. Chem Rev 1999, 99, 3181.
11. Flory, P. J. Principles of Polymer Chemistry; Cornell Univer-
sity Press: Ithaca, 1953.
12. Jones, R. A. L. Soft Condensed Matter; Oxford University
Press: New York, 2002.
13. Badarau, C.; Wang, Z. Y. Macromolecules 2003, 36, 6959.
14. Watanabe, S.; Ichimura, K. J Polym Sci Polym Chem Ed 1982,
20, 3261.
15. Zheng, Y.; Micic, M.; Mello, S. V.; Mabrouki, M.; Andreo-
poulos, F. M.; Konka, V.; Pham, S. M.; Leblanc, R. M. Macro-
molecules 2002, 35, 5228.
16. Tran Cong, Q.; Nagaki, T.; Nakagawa, T.; Yano, O.; Soen, T.
Macromolecules 1989, 22, 2720.
17. Nakabayashi, K.; Schwalm, R.; Schnabel, W. Angew Makro-
mol Chem 1992, 195, 191.
18. Grassie, N.; Weir, N. A. J Appl Polym Sci 1965, 9, 975.
19. Wells, R. K.; Royston, A.; Badyal, J. P. S. Macromolecules
1994, 27, 7465.
20. Toomey, R.; Freidank, D.; Ruehe, J. Macromolecules 2004, 37,
882.
21. Al Akhrass, S.; Ostaci, R. V.; Grohens, Y.; Drockenmuller, E.;
Reiter, G. Langmuir 2008, 24, 1884.
22. Cai, S. X.; Glenn, D. J.; Kanskar, M.; Wybourne, M. N.; Keana,
J. F. W. Chem Mater 1994, 6, 1822.
23. Carroll, G. T.; Sojka, M. E.; Lei, X. G.; Turro, N. J.; Koberstein,
J. T. Langmuir 2006, 22, 7748.
24. Torikai, A.; Takeuchi, T.; Fueki, K. Polym Photochem 1983, 3,
307.
25. Jockusch, S.; Turro, N. J.; Mitsukami, Y.; Matsumoto, M.; Iwa-
mura, T.; Lindner, T.; Flohr, A.; di Massimo, G. J Appl Polym
Sci 2009, 111, 2163.
26. Turro, N. J. Modern Molecular Photochemistry; University Sci-
ence Books: Sausalito, CA, 1991.
27. Hild, G. Prog Polym Sci 1998, 23, 1019.
28. Yamane, Y.; Ando, I.; Buchholz, F. L.; Reinhardt, A. R.;
Schlick, S. Macromolecules 2004, 37, 9841.
29. Stejskal, E. O.; Tanner, J. E. J Chem Phys 1965, 42, 288.
30. Aluas, M.; Filip, C. Solid State Nucl Magn Reson 2005, 27, 165.
Figure 6 EPR spectra of 4-oxo-tempo in photo-generated
gels from (a) BP and (b) bis-BP.
PHOTOGENERATION OF GELATINOUS NETWORKS 173
Journal of Applied Polymer Science DOI 10.1002/app
7. 31. Hou, S.-S.; Graf, R.; Spiess, H. W.; Kuo, P.-L. Macromol Rapid
Commun 2001, 22, 1386.
32. English, A. D.; Chase, D. B.; Spinelli, H. J. Macromolecules
1983, 16, 1422.
33. Goel, N.; Shah, S. N.; Yuan, W. -L.; O’Rear, E. A. J Appl
Polym Sci 2001, 82, 2978.
34. Ellul, M. D.; Tsou, A. H.; Hu, W. Polymer 2004, 45, 3351.
35. Peacock, A.; Calhoun, A. Polymer Chemistry: Properties and
Applications; Hanser: Munich, 2006.
36. Flory, P. J.; Rehner, J., Jr. J Chem Phys 1943, 11, 521.
37. Flory, P. J. J Chem Phys 1950, 18, 108.
38. Brandrup, J.; Immergut, E. H., Eds. Polymer Handbook, 4th
ed.; Wiley-Interscience: New York, 1998.
39. Weil, J. A.; Bolton, J. R.; Wertz, J. E. Electron Paramagnetic
Resonance: Elementary Theory and Practical Applications.
Wiley Interscience: New York, 1994.
40. Mammana, A.; D’Urso, A.; Lauceri, R.; Purrello, R. J Am
Chem Soc 2007, 129, 8062.
41. Randazzo, R.; Mammana, A.; D’Urso, A.; Lauceri, R.; Purrello,
R. Angew Chem Int Ed 2008, 47, 9879.
174 CARROLL ET AL.
Journal of Applied Polymer Science DOI 10.1002/app