- There are several methods to measure the average molecular weight of polymers, including end-group analysis, colligative properties, light scattering, and ultracentrifugation.
- The molecular weight distribution and average molecular weights determine important properties like viscosity and processability.
- Common averages include the number-average molecular weight (Mn), weight-average molecular weight (Mw), and viscosity-average molecular weight (Mv). The ratio of Mw/Mn is called the polydispersity index (PDI).
- Techniques like end-group analysis and colligative properties work best for lower molecular weights, while light scattering and ultracentrifugation can measure wider ranges up to 100,
This document discusses molecular weight of polymers. It defines molecular weight as the sum of atomic weights of atoms in a molecule. Polymers have extremely high molecular weights due to their long molecular chains. There are different types of average molecular weights including number average, weight average, viscosity average, and z-average. Molecular weight distribution is also discussed. Higher molecular weight increases properties like ductility, impact resistance, weather resistance but also increases viscosity making processing more difficult.
The document discusses the molecular weight of polymers and methods to determine it, focusing on membrane osmometry.
[1] Membrane osmometry uses a semipermeable membrane to separate a dilute polymer solution from pure solvent. The osmotic pressure across the membrane is measured and used to calculate the number average molecular weight of the polymer.
[2] Factors that affect molecular weight determination include concentration, temperature, and interactions between polymer and solvent. The van't Hoff equation relates osmotic pressure and concentration for ideal solutions, while real solutions require additional terms.
[3] A worked example demonstrates using osmotic pressure measurements at different concentrations to calculate the molecular weight and second vi
The document discusses crystallization and crystallinity of polymers. It defines crystallinity as the degree of structural order in a solid, where the atoms or molecules are arranged in a regular, periodic manner. Crystalline polymers have long-range order arrangement of some segments of polymer chains, while amorphous polymers do not have any degree of crystallinity. Crystallinity depends on factors like length and branching of polymer chains. Methods to evaluate crystallinity include differential scanning calorimetry, X-ray diffraction, infrared spectroscopy, and nuclear magnetic resonance. Crystallinity affects important physical properties of polymers.
Emulsion polymerization involves radical chain polymerization where monomers are dispersed as droplets in water and polymerize within micelles. It allows for high molecular weight polymers to form at high reaction rates. The process involves four main components: 1) monomers, 2) a dispersion medium (water), 3) an emulsifier, and 4) a water-soluble initiator. Polymerization occurs only within the micelles. The mechanism proceeds in three stages: initiation within the micelles, monomer diffusion into particles as conversion increases, and consumption of monomer droplets. Emulsion polymerization produces polymer latex particles and addresses heat transfer and viscosity issues relative to other polymerization methods.
Copolymerization involves polymerizing two or more different monomers simultaneously so that the resulting polymer contains more than one type of repeating unit in the polymer chain. There are several types of copolymers including random, alternating, block, and graft copolymers. The composition of a copolymer depends on factors like the monomer concentrations and their reactivity ratios. Kinetic models can be used to predict the monomer composition of the copolymer based on the monomer feed using methods like the Mayo-Lewis equation or the Fineman-Ross equation. The reactivity ratios influence whether an ideal random copolymer, alternating copolymer, or block copolymer will form. Ionic copolymerization
Determining molecular weights of polymers is important because it controls properties like solubility, elasticity, and mechanics. Polymers do not have uniform molecular weights but a distribution of different sizes. Molecular weight can be determined through various physical and chemical methods like end group analysis, light scattering, viscosity measurements, and gel permeation chromatography. These methods provide information about the number average molecular weight and distribution across molecules in a sample.
This document summarizes key aspects of polymer science including polymerization, monomers, and polymerization mechanisms. It discusses that polymerization is the process that links monomer molecules into polymer chains. There are different polymerization mechanisms including chain-growth and free radical polymerization. Chain-growth polymerization proceeds through initiation, propagation, and termination steps. Free radical polymerization uses initiators to generate free radicals to start the polymerization reaction. The document provides examples of monomers and initiators and discusses how functionality of monomers affects the structure of the resulting polymer chains.
This document discusses molecular weight of polymers. It defines molecular weight as the sum of atomic weights of atoms in a molecule. Polymers have extremely high molecular weights due to their long molecular chains. There are different types of average molecular weights including number average, weight average, viscosity average, and z-average. Molecular weight distribution is also discussed. Higher molecular weight increases properties like ductility, impact resistance, weather resistance but also increases viscosity making processing more difficult.
The document discusses the molecular weight of polymers and methods to determine it, focusing on membrane osmometry.
[1] Membrane osmometry uses a semipermeable membrane to separate a dilute polymer solution from pure solvent. The osmotic pressure across the membrane is measured and used to calculate the number average molecular weight of the polymer.
[2] Factors that affect molecular weight determination include concentration, temperature, and interactions between polymer and solvent. The van't Hoff equation relates osmotic pressure and concentration for ideal solutions, while real solutions require additional terms.
[3] A worked example demonstrates using osmotic pressure measurements at different concentrations to calculate the molecular weight and second vi
The document discusses crystallization and crystallinity of polymers. It defines crystallinity as the degree of structural order in a solid, where the atoms or molecules are arranged in a regular, periodic manner. Crystalline polymers have long-range order arrangement of some segments of polymer chains, while amorphous polymers do not have any degree of crystallinity. Crystallinity depends on factors like length and branching of polymer chains. Methods to evaluate crystallinity include differential scanning calorimetry, X-ray diffraction, infrared spectroscopy, and nuclear magnetic resonance. Crystallinity affects important physical properties of polymers.
Emulsion polymerization involves radical chain polymerization where monomers are dispersed as droplets in water and polymerize within micelles. It allows for high molecular weight polymers to form at high reaction rates. The process involves four main components: 1) monomers, 2) a dispersion medium (water), 3) an emulsifier, and 4) a water-soluble initiator. Polymerization occurs only within the micelles. The mechanism proceeds in three stages: initiation within the micelles, monomer diffusion into particles as conversion increases, and consumption of monomer droplets. Emulsion polymerization produces polymer latex particles and addresses heat transfer and viscosity issues relative to other polymerization methods.
Copolymerization involves polymerizing two or more different monomers simultaneously so that the resulting polymer contains more than one type of repeating unit in the polymer chain. There are several types of copolymers including random, alternating, block, and graft copolymers. The composition of a copolymer depends on factors like the monomer concentrations and their reactivity ratios. Kinetic models can be used to predict the monomer composition of the copolymer based on the monomer feed using methods like the Mayo-Lewis equation or the Fineman-Ross equation. The reactivity ratios influence whether an ideal random copolymer, alternating copolymer, or block copolymer will form. Ionic copolymerization
Determining molecular weights of polymers is important because it controls properties like solubility, elasticity, and mechanics. Polymers do not have uniform molecular weights but a distribution of different sizes. Molecular weight can be determined through various physical and chemical methods like end group analysis, light scattering, viscosity measurements, and gel permeation chromatography. These methods provide information about the number average molecular weight and distribution across molecules in a sample.
This document summarizes key aspects of polymer science including polymerization, monomers, and polymerization mechanisms. It discusses that polymerization is the process that links monomer molecules into polymer chains. There are different polymerization mechanisms including chain-growth and free radical polymerization. Chain-growth polymerization proceeds through initiation, propagation, and termination steps. Free radical polymerization uses initiators to generate free radicals to start the polymerization reaction. The document provides examples of monomers and initiators and discusses how functionality of monomers affects the structure of the resulting polymer chains.
Polymerization Process and its Advantages , Disadvantage
1.Bulk Polymerization Process
2.Solution Polymerization Process
3.Suspension Polymerization Process
4.Emulsion Polymerization Process
Polymer Rheology(Properties study of polymer)Haseeb Ahmad
This document discusses fundamentals of polymer rheology. It defines rheology as the study of flow of matter, primarily liquids but also soft solids. Rheology is important for characterizing polymers and understanding how polymer structure affects processing behavior. The document describes different types of fluids and their viscosity properties. It also discusses various rheological measurement techniques like rotational rheometers, capillary rheometers and melt flow indexers.
It consists classification of polymerization techniques. What is bulk polymerization, how will the reaction proceed, and what are the advantages, disadvantages, and applications. Similarly, what is solution polymerization and how it will be carried out, what are the advantages, disadvantages, and applications behind it everything is explained in detail. Some of the related questions are also included for practice. All the contents taken from different websites and books are also mentioned.
- Polymers are giant molecules formed by linking together small repeating units called monomers via covalent bonds. There are three main types of polymerization: addition, condensation, and copolymerization.
- Properties of polymers depend on factors like the monomer type, the degree of polymerization, tacticity, and whether the polymer is crystalline or amorphous. Common polymers include polyethylene, polypropylene, nylon, polyethylene terephthalate.
- Natural rubbers are polymers of the monomer isoprene that provide flexibility and elasticity. However, natural rubber has limitations that are overcome through vulcanization, which introduces cross-links between polymer chains through the addition of sulfur.
Determination of molecular weight of polymers by visometryudhay roopavath
This document discusses methods for determining the molecular weight of polymers using viscometry. It defines various types of average molecular weights and explains how intrinsic viscosity is measured through polymer solution viscosity. Viscosity measurements are used to calculate intrinsic viscosity and relate it to molecular weight through the Mark-Houwink-Sakurada equation. Double extrapolation plots of reduced viscosity and inherent viscosity versus concentration are used to determine intrinsic viscosity.
This document provides an introduction to polymer science, including definitions of key terms like polymer, monomer, oligomer, and degree of polymerization. It discusses various classifications of polymers such as by origin, monomer composition (homopolymer, copolymer), chain structure, configuration, and thermal behavior. Mechanisms of polymerization including step-growth and chain-growth are introduced. Physical properties of polymers related to their structure like crystallinity, glass transition temperature, and elastomers are also covered.
The document discusses the molecular weight of polymers. It defines molecular weight as the sum of the atomic weights of all the atoms in a polymer molecule. There are two types of average molecular weights - number average molecular weight (Mn) and weight average molecular weight (Mw). Mn is calculated by dividing the total weight of polymer molecules by the total number of molecules, while Mw takes into account that larger molecules contribute more to the total mass. Mw is always higher than Mn. Molecular weight affects various properties - higher molecular weight increases mechanical properties but lowers thermal properties. Various techniques can be used to determine molecular weight and its distribution.
Condensation polymerization involves monomers with functional groups like alcohols and carboxylic acids. During condensation polymerization, these functional groups react to form polymer chains, releasing small molecules like water or methanol as byproducts. This results in strong covalent bonds between the monomers, such as amide or ester linkages. Common examples of condensation polymerization are the reaction of a carboxylic acid and amine to form an amide linkage, or a carboxylic acid and alcohol to form an ester linkage. Condensation polymerization is an important process that allows for the production of many plastics and other materials.
Average molecular weight of polymer
-Number average molecular weight
-Weight average molecular weight
Properties of Polymer
Uses/Application of Polymer
Polymers are macromolecules formed by linking together small repeating units called monomers. There are two main types of polymerization: addition and condensation. Addition polymers are formed without the elimination of small molecules when monomers containing carbon-carbon double bonds polymerize via a chain reaction mechanism involving three steps: initiation, propagation, and termination. Condensation polymers are formed with the elimination of small molecules like water or ammonia when bifunctional monomers react. Common examples of addition polymerization include polyethylene formed from ethylene monomers using a free radical initiator like benzoyl peroxide.
Structure property relationship in polymerRashidul Islam
This document discusses the relationship between polymer structure and properties such as solubility, glass transition temperature, thermal stability, and tensile strength. It explains that solubility decreases with longer branches or crosslinking. Glass transition temperature decreases with increased chain flexibility or bulky side groups but increases with crosslinking. Thermal stability is highest in polymers with aromatic or fluorine groups. Tensile strength follows the order branched < linear < crosslinked.
This document provides an overview of polymers, including their classification, characterization techniques, and examples. It begins with an introduction to polymers, noting they are macromolecules composed of repeating structural units or monomers linked together. The document then discusses various polymer classifications including source, structure, and interaction with water. Several characterization techniques are outlined, such as tensile strength testing, X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry. Specific techniques like atomic force microscopy and X-ray photoelectron spectroscopy are also summarized. The document concludes with examples of characterization applications.
Polymer science: preparation and uses of polymersVARSHAAWASAR
Polymers are large molecules formed by combining many smaller molecules called monomers. They are made through polymerization reactions where monomers join together in chains. There are two main types of polymerization - addition and condensation. Polymers have a wide variety of applications including plastics, fibers, elastomers and more. Their properties depend on factors like molecular structure and weight. Thermal analysis techniques are used to characterize polymers and determine properties like glass transition temperature. Biodegradable polymers break down over time and have applications in drug delivery.
Polymer science deals with large macromolecules formed by bonding many small monomer units together. There are two main types of polymerization: addition polymerization and condensation polymerization. In addition polymerization, monomers add together through a chain reaction of initiation, propagation, and termination steps. Condensation polymers form when monomers bond together while releasing small molecules, like water. Polymers can be classified in various ways, including their source, monomer composition, chain structure, and properties like being thermoplastic or thermosetting. Common polymers have a wide range of applications as plastics, fibers, elastomers, and more.
1. Polymers are large molecules formed by linking together many smaller molecules called monomers. Examples include polyethene formed from linking ethene molecules.
2. Polymers have both crystalline regions that provide strength and amorphous regions that provide flexibility. Their properties depend on their size, shape, and intermolecular forces.
3. Polymers can be classified based on the number of monomers (homo- vs copolymers), the arrangement of monomers (tacticity), functionality (linear, branched, or network), and origin (natural, synthetic, or inorganic).
This document provides an introduction to polymers. It discusses that polymers are formed through polymerization reactions where small monomer units join together to create large polymer molecules. There are two main types of polymerization - addition and condensation polymerization. Polymers can be classified as homopolymers, formed from one monomer, or copolymers, formed from multiple monomers. The document also discusses important polymer properties like glass transition temperature, molecular weight, types of polymers including thermoplastics and thermosets, and basic mechanical properties.
The document discusses molecular weight (MW) and its importance in determining polymer properties. It provides the following key points:
- Polymer properties depend on chain length, which is expressed by MW. Higher MW leads to better mechanical strength but poorer processability.
- Synthetic polymers are polydisperse, with a distribution of chain lengths and MWs. Various average MW values are used like number average MW (Mn) and weight average MW (Mw).
- MW distribution describes the relationship between number of moles of each polymer species and its molar mass. Broader distributions yield better impact resistance while narrower distributions give more uniform properties.
- Degree of polymerization (DP) represents the
Gel permeation chromatography (GPC) is a type of size exclusion chromatography used to analyze polymers. In GPC, polymer samples are separated based on molecular size as they pass through a column containing porous beads. Larger polymer molecules elute from the column first as they are excluded from the pores, while smaller molecules penetrate deeper and elute later. This allows the whole molecular mass distribution of a polymer sample to be measured. Calibration with polymer standards of known molecular weights is required to determine molecular weights of analyzed polymers. GPC provides information on molecular weight averages and dispersity.
Polymerization Process and its Advantages , Disadvantage
1.Bulk Polymerization Process
2.Solution Polymerization Process
3.Suspension Polymerization Process
4.Emulsion Polymerization Process
Polymer Rheology(Properties study of polymer)Haseeb Ahmad
This document discusses fundamentals of polymer rheology. It defines rheology as the study of flow of matter, primarily liquids but also soft solids. Rheology is important for characterizing polymers and understanding how polymer structure affects processing behavior. The document describes different types of fluids and their viscosity properties. It also discusses various rheological measurement techniques like rotational rheometers, capillary rheometers and melt flow indexers.
It consists classification of polymerization techniques. What is bulk polymerization, how will the reaction proceed, and what are the advantages, disadvantages, and applications. Similarly, what is solution polymerization and how it will be carried out, what are the advantages, disadvantages, and applications behind it everything is explained in detail. Some of the related questions are also included for practice. All the contents taken from different websites and books are also mentioned.
- Polymers are giant molecules formed by linking together small repeating units called monomers via covalent bonds. There are three main types of polymerization: addition, condensation, and copolymerization.
- Properties of polymers depend on factors like the monomer type, the degree of polymerization, tacticity, and whether the polymer is crystalline or amorphous. Common polymers include polyethylene, polypropylene, nylon, polyethylene terephthalate.
- Natural rubbers are polymers of the monomer isoprene that provide flexibility and elasticity. However, natural rubber has limitations that are overcome through vulcanization, which introduces cross-links between polymer chains through the addition of sulfur.
Determination of molecular weight of polymers by visometryudhay roopavath
This document discusses methods for determining the molecular weight of polymers using viscometry. It defines various types of average molecular weights and explains how intrinsic viscosity is measured through polymer solution viscosity. Viscosity measurements are used to calculate intrinsic viscosity and relate it to molecular weight through the Mark-Houwink-Sakurada equation. Double extrapolation plots of reduced viscosity and inherent viscosity versus concentration are used to determine intrinsic viscosity.
This document provides an introduction to polymer science, including definitions of key terms like polymer, monomer, oligomer, and degree of polymerization. It discusses various classifications of polymers such as by origin, monomer composition (homopolymer, copolymer), chain structure, configuration, and thermal behavior. Mechanisms of polymerization including step-growth and chain-growth are introduced. Physical properties of polymers related to their structure like crystallinity, glass transition temperature, and elastomers are also covered.
The document discusses the molecular weight of polymers. It defines molecular weight as the sum of the atomic weights of all the atoms in a polymer molecule. There are two types of average molecular weights - number average molecular weight (Mn) and weight average molecular weight (Mw). Mn is calculated by dividing the total weight of polymer molecules by the total number of molecules, while Mw takes into account that larger molecules contribute more to the total mass. Mw is always higher than Mn. Molecular weight affects various properties - higher molecular weight increases mechanical properties but lowers thermal properties. Various techniques can be used to determine molecular weight and its distribution.
Condensation polymerization involves monomers with functional groups like alcohols and carboxylic acids. During condensation polymerization, these functional groups react to form polymer chains, releasing small molecules like water or methanol as byproducts. This results in strong covalent bonds between the monomers, such as amide or ester linkages. Common examples of condensation polymerization are the reaction of a carboxylic acid and amine to form an amide linkage, or a carboxylic acid and alcohol to form an ester linkage. Condensation polymerization is an important process that allows for the production of many plastics and other materials.
Average molecular weight of polymer
-Number average molecular weight
-Weight average molecular weight
Properties of Polymer
Uses/Application of Polymer
Polymers are macromolecules formed by linking together small repeating units called monomers. There are two main types of polymerization: addition and condensation. Addition polymers are formed without the elimination of small molecules when monomers containing carbon-carbon double bonds polymerize via a chain reaction mechanism involving three steps: initiation, propagation, and termination. Condensation polymers are formed with the elimination of small molecules like water or ammonia when bifunctional monomers react. Common examples of addition polymerization include polyethylene formed from ethylene monomers using a free radical initiator like benzoyl peroxide.
Structure property relationship in polymerRashidul Islam
This document discusses the relationship between polymer structure and properties such as solubility, glass transition temperature, thermal stability, and tensile strength. It explains that solubility decreases with longer branches or crosslinking. Glass transition temperature decreases with increased chain flexibility or bulky side groups but increases with crosslinking. Thermal stability is highest in polymers with aromatic or fluorine groups. Tensile strength follows the order branched < linear < crosslinked.
This document provides an overview of polymers, including their classification, characterization techniques, and examples. It begins with an introduction to polymers, noting they are macromolecules composed of repeating structural units or monomers linked together. The document then discusses various polymer classifications including source, structure, and interaction with water. Several characterization techniques are outlined, such as tensile strength testing, X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry. Specific techniques like atomic force microscopy and X-ray photoelectron spectroscopy are also summarized. The document concludes with examples of characterization applications.
Polymer science: preparation and uses of polymersVARSHAAWASAR
Polymers are large molecules formed by combining many smaller molecules called monomers. They are made through polymerization reactions where monomers join together in chains. There are two main types of polymerization - addition and condensation. Polymers have a wide variety of applications including plastics, fibers, elastomers and more. Their properties depend on factors like molecular structure and weight. Thermal analysis techniques are used to characterize polymers and determine properties like glass transition temperature. Biodegradable polymers break down over time and have applications in drug delivery.
Polymer science deals with large macromolecules formed by bonding many small monomer units together. There are two main types of polymerization: addition polymerization and condensation polymerization. In addition polymerization, monomers add together through a chain reaction of initiation, propagation, and termination steps. Condensation polymers form when monomers bond together while releasing small molecules, like water. Polymers can be classified in various ways, including their source, monomer composition, chain structure, and properties like being thermoplastic or thermosetting. Common polymers have a wide range of applications as plastics, fibers, elastomers, and more.
1. Polymers are large molecules formed by linking together many smaller molecules called monomers. Examples include polyethene formed from linking ethene molecules.
2. Polymers have both crystalline regions that provide strength and amorphous regions that provide flexibility. Their properties depend on their size, shape, and intermolecular forces.
3. Polymers can be classified based on the number of monomers (homo- vs copolymers), the arrangement of monomers (tacticity), functionality (linear, branched, or network), and origin (natural, synthetic, or inorganic).
This document provides an introduction to polymers. It discusses that polymers are formed through polymerization reactions where small monomer units join together to create large polymer molecules. There are two main types of polymerization - addition and condensation polymerization. Polymers can be classified as homopolymers, formed from one monomer, or copolymers, formed from multiple monomers. The document also discusses important polymer properties like glass transition temperature, molecular weight, types of polymers including thermoplastics and thermosets, and basic mechanical properties.
The document discusses molecular weight (MW) and its importance in determining polymer properties. It provides the following key points:
- Polymer properties depend on chain length, which is expressed by MW. Higher MW leads to better mechanical strength but poorer processability.
- Synthetic polymers are polydisperse, with a distribution of chain lengths and MWs. Various average MW values are used like number average MW (Mn) and weight average MW (Mw).
- MW distribution describes the relationship between number of moles of each polymer species and its molar mass. Broader distributions yield better impact resistance while narrower distributions give more uniform properties.
- Degree of polymerization (DP) represents the
Gel permeation chromatography (GPC) is a type of size exclusion chromatography used to analyze polymers. In GPC, polymer samples are separated based on molecular size as they pass through a column containing porous beads. Larger polymer molecules elute from the column first as they are excluded from the pores, while smaller molecules penetrate deeper and elute later. This allows the whole molecular mass distribution of a polymer sample to be measured. Calibration with polymer standards of known molecular weights is required to determine molecular weights of analyzed polymers. GPC provides information on molecular weight averages and dispersity.
This presentation discusses methods for determining the number average molecular weight (Mn) of polymers. It describes techniques such as cryoscopy (freezing point depression), ebullioscopy (boiling point elevation), and osmometry including vapor phase osmometry and membrane osmometry. It also discusses end group analysis and how it can be used to calculate Mn by determining the functionality of end groups. The techniques vary in the molecular weight ranges they are applicable to, with cryoscopy and ebullioscopy typically able to measure up to Mn of 30,000 and osmometry and end group analysis having broader ranges.
The document discusses analytical ultracentrifugation (AUC), which is a technique used to determine properties of macromolecules like molar mass, size, and state of association in solution. There are two main types of AUC experiments - sedimentation velocity and sedimentation equilibrium. Sedimentation velocity measurements analyze sedimentation profiles to determine values like sedimentation coefficient, while sedimentation equilibrium measurements analyze concentration gradients to directly determine molar mass and state of association. AUC provides advantages over other techniques like determining absolute molar mass over a large range and ability to study weakly linked assemblies without disruption.
This research article describes a study using multi-angle laser light scattering to determine the molecular weights of two polystyrene polymer solutions. The molecular weights measured were 388,300±16,500 g/mol and 915,300±44,800 g/mol, which were within 2.7% of the known values for the solutions. The article provides background on static light scattering analysis and the Zimm plot method used to calculate molecular weight and radius of gyration from light scattering intensity measurements taken at varying angles.
Foundation Part 1- Polymers and MW.pptWasifRazzaq2
This document introduces polymers and molecular weight. It discusses how polymers are long chains of repeating monomer units that can vary in chemical structure, 3D shape, monomer type, and chain length distribution. Molecular weight describes the average length of polymer chains, with higher molecular weight indicating longer chains. The molecular weight distribution is important, as it characterizes the range of chain lengths in a sample and influences properties like strength, toughness and processability. Gel permeation chromatography is described as the primary method for measuring molecular weight distributions.
- Polymer molecular weight determines many physical properties like transition temperatures and mechanical properties.
- Molecular weight distributions are described using average values like number average (MN), weight average (MW), and viscosity average (MV).
- For condensation polymers formed from bifunctional monomers, the most probable molecular weight distribution was derived by Flory. It results in a monotonically decreasing function with the monomer being the most probable species even at high conversion.
This document summarizes an experiment analyzing biofuels synthesized from corn oil using gas chromatography-mass spectrometry (GC-MS). Two reaction conditions were tested: 1:6/1 wt% and 1:6/3 wt% oil to methanol ratios. GC-MS analysis found glycerin and fatty acid methyl esters in both conditions as expected. Some unique compounds and constitutional isomers were produced depending on the reaction condition. Mass spectra of the main compounds, like glycerin and a fatty acid methyl ester, were similar between conditions. The results were consistent with the proposed reaction for biodiesel synthesis.
1. The document discusses additive manufacturing and 3D printing of polymers. It notes that polymers are among the cheapest materials for 3D printing and lists some common plastics used, including ABS, PLA, polyamide, and nylon.
2. The document then covers various topics related to polymers, including classifications of polymers, molecular weight, polymer processing techniques, and metal powder characterization. It provides examples and definitions for these topics.
3. The remainder of the document discusses powder metallurgy processing techniques like compaction, sintering, defects in sintering, and applications of powder metallurgy. Processing steps like die pressing, CIP, HIP, slip casting, and
This document describes an experiment to synthesize copolymers of myrcene with maleic anhydride or tert-butyl acrylate using nitroxide mediated polymerization with NHS-BlocBuilder initiator. Myrcene/maleic anhydride copolymerization was unsuccessful likely due to a side Diels-Alder reaction between the monomers. Myrcene/tert-butyl acrylate copolymerizations with varying monomer feed compositions were more controlled. Analysis of the copolymers found decreasing molecular weight and low polydispersity as the tert-butyl acrylate content increased, possibly due to intramolecular backbiting terminations.
Osmotic pressure and light scattering methods are used to determine the number-average and weight-average molecular weights of polymers in solution. Polymers can be characterized as amorphous, semicrystalline, or crystalline depending on their chain structure and interactions. Thermoplastics exhibit glass transitions and/or melting points while thermosets only exhibit glass transitions.
2D gel electrophoresis is a powerful technique that separates proteins based on two properties - their isoelectric point and molecular weight. In the first dimension, isoelectric focusing separates proteins based on isoelectric point, while SDS-PAGE in the second dimension separates them based on molecular weight. Each spot on the 2D gel corresponds to a single protein that can then be analyzed by mass spectrometry. This technique allows for the high-throughput separation and analysis of thousands of proteins from biological samples.
Sedimentation for determining molecular weight of macromoleculesShubhangiSuri1
Process of sedimentation with mechanism of action and mathematical derivations, different methods for separation of macromolecules by sedimentation, viscometry vs sedimentation
The document summarizes a summer training report on the characterization of 8 mole% yttria stabilized zirconia obtained from different sources. The objectives were to characterize and compare YSZ powders from ISRO, IRE and TOSOH, and to optimize sintering conditions to achieve high density pellets suitable for use as a solid oxide fuel cell electrolyte. Characterization techniques included tap density measurement, BET surface area analysis, X-ray diffraction for phase analysis, particle size distribution analysis, and density measurement of sintered pellets.
Analytical Ultracentrifugation of protein.DiNa Amin
Ultracentrifuge is a high-speed centrifuge for separating microscopic and sub-microscopic materials to determine the sizes and molecular weights of colloidal and other small particles.
Molecular weight determination of polymers by viscometrymisha minaal
This document discusses methods for determining the molecular weight of polymers using viscometry. It explains that viscosity is related to molecular weight through equations like the Mark-Houwink and Flory-Fox equations. An Ubbelohde viscometer is commonly used to measure the viscosity of polymer solutions and calculate values like intrinsic viscosity. These viscosity values can then be used in the equations to determine the average molecular weight of the polymer. The document also discusses how melt viscosity relates to molecular weight for linear polymers.
1) The study experimentally evaluated the compatibility relationship between polymer solutions and oil layers through core flooding tests with different permeability cores.
2) The results showed that injection rate decreased with increasing polymer concentration and molecular weight, and increased with permeability.
3) Based on the results, boundaries for injection capability were established and a compatibility chart was proposed to guide polymer solution selection for different sedimentary microfacies in the field based on permeability and pore size.
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Polymer Molecular weight and its Measurement methods.pptx
1. Polymer Molecular weight and its
Measurement methods
At the end of this lecture, you should be able to:
- Understand the distribution of polymer M.wt.
- Learn the ways to present the average M.wt
- Understand the measurement methods of polymer average M.wt.
- Calculate polymer average M.wt using different formula.
Feb. 2019
Mustansiriyah University/ Materials Eng. Dept.
Dr Ahmed AYASH
2. Molecular Weight:
Molecular weight of a chemical compound can be defined, simply, as the sum of the atomic weights of each of the
atoms in the molecule.
Examples:
Water (H2O) is 2 H (1g) and one O (16g) = 2*(1) + 1*(16)= 18 g/mol
Methane CH4 is 1 C (12g) and 4 H (1g)= 1*(12) + 4 *(1) = 16 g/mole
Polyethylene -(C2H4)-1000 = 2 C (12g) + 4H (1g) = 28g/mole * 1000 = 28,000 g/mole
Average Molecular Weight
Polymers are made up of many molecular weights or a distribution of chain lengths. In other other words, if one
takes polyethylene as an example, this polymer may have chains of ethylene (C2H4) with different lengths; some
longer than others.
Example:
Polyethylene -(C2H4)-1000 has some chains with 1001 repeating ethylene units, some with 1010 ethylene units,
some with 999 repeating units, and some with 990 repeating units. The average number of repeating units or
chain length is 1000 repeating ethylene units for a molecular weight of 28*1000 or 28,000 g/mole .
Therefore, polymers must be represented by the value of average molecular weight. 2
4. There are four ways to represent the average molecular weight:
(1) Number-average molecular weight (Mn) for a discrete distribution of molecular weights is given as:
where Ni indicates the number of moles of molecules having a molecular weight of Mi and Wi, is the weight
of molecules with molecular weight Mi. Thus, Wi = Ni Mi.
The expression for the number-average molecular weight of a continuous distribution function is:
4
5. (3) Z-average molecular weight (Mz) for a discrete distribution of molecular weights is given as:
(2) Weight-average molecular weight (Mw) for a discrete distribution of molecular weights is given as:
The expression for the weight-average molecular weight of a continuous distribution function is:
5
6. (4) Viscosity-average molecular weight (Mv) can be obtained, experimentally, from dilute-solution
viscometer using Mark-Howink equation. The viscosity-average molecular weight falls between Mn and
Mw depending upon whether the solvent is a good or poor solvent for the polymer. In the case of a good
solvent, Mv = Mw .
- Mark-Howink-Sakurada equation:
NOTES:
1. A measure of the breadth of the molecular-weight distribution is given by the ratios of molecular-weight
averages. For this purpose, the most commonly used ratio is Mw/Mn ,called the polydispersity index or PDI.
PDI =
𝑀𝑤
𝑀𝑛
> 1 ; polymers having PDI = 1 are called monodiseperse polymers
2. Degree of Polymerization (DP): is the number of monomeric units in a macromolecule or polymer or
oligomer (consists of a few repeating units Or DP is the number of repeat units.
DPw =
𝑀𝑤
𝑀𝑜
, DPn =
𝑀𝑛
𝑀𝑜
; where M0 is the monomer molecular weight. 6
9. There are several reasons why we might want to measure polymer average molecular weight and its
distribution:
1. The molecular weight and its distribution determine the viscous and elastic properties of the molten polymer.
This affects the processibility of the melt and also the behavior of the resulting solid material. For example, a
resin suitable for extrusion must have a high viscosity at low shear rates so that the extrudate maintains its
integrity. To be suitable for injection molding, however, the same resin must have a low viscosity at high shear
rates so that the injection pressure not be excessive.
2. The molecular weight of a polymer can determine its applications. For example, the resin used for making
polycarbonate water bottles, for example, differs significantly in molecular weight from the polycarbonate that
goes into compact disks.
3. Differences in molecular weight distribution also influence the polymer properties. As a consequence, two
chemically similar polymers, processed identically, that have the same molecular weight but different
molecular-weight distributions may result in products that show significantly different shrinkages, tensile
properties, and failure properties. For this very important reason, it is advantageous to know the molecular
weight and molecular-weight distribution of the polymers used.
4. Other situations where the molecular weight and its distribution directly influence results include phase
equilibrium and crystallization kinetics. 9
10. Example 2.1:
A polydisperse sample of polystyrene is prepared by mixing three monodisperse samples in the following proportions:
1 g 10,000 molecular weight
2 g 50,000 molecular weight
2 g 100,000 molecular weight
Using this information, calculate the number-average molecular weight, weight- average molecular weight, and PDI of
the mixture.
Solution:
10
11. Example 2.2:
A polymer is fractionated and is found to have the continuous molecular-weight distribution shown below as
a plot of the weight, W, of molecules having molecular weight, M, versus W. Given this molecular-weight
distribution, calculate Mn and Mw.
Solution:
11
12. M.wt Measurement Methods
Number average
M.wt
END-GROUP
ANALYSIS
COLLIGATIVE
PROPERTIES
Viscosity average M.wt
Viscometry
Weight average
M.wt
Light Scattering
Z-average M.wt
Ultracentrifugation
Gel Permeation Chromatography (GPC)
12
NOTE: The choice of method for polymer molecular weight determination is influenced by factors such as:
(i) information required, (ii) operative region, (iii) cost effectiveness, and (iv) experimental conditions and
requirements.
13. End-group Analysis
This method has presumed importance particularly in the determination of average molecular weight of
step-growth polymers (condensation). Consider the step-wise condensation polymerization of polyesters:
Under the assumption that each polymer chain contains one – OH and one – COOH groups, direct
measurement of the concentration of the groups can be done using chemical (titrimetric or pH
measurement) or spectroscopic (infrared or nuclear magnetic) techniques. This is also applicable to other
step-growth polymers.
LIMITATIONS:
1. The major setback of this technique is the decrease in sensitivity with increasing polymer chain length.
This method is restricted to polymer with molecular weight 20,000 amu. Aside this, it requires high
concentration of polymer.
2. This method requires that the polymer be free of impurities and other groups present in the chain
should not interfere in the determination of end group of interest.
13
14. colligative properties
The relations between the colligative properties and molecular weight for infinitely dilute solutions in a fact
that the activity of the solute in a solution becomes equal to its mole fraction as the solute concentration
becomes sufficiently small.
This method is based on:
•Vapour-pressure lowering,
•Boiling-point elevation (ebulliometry),
•Freezing-point depression (cryoscopy),
•Osmotic pressure (osmometry).
where
∆Tb, ∆Tf, and π are the boiling-point elevation, freezing-point depression, and osmotic pressure, respectively.
ρ is the density of the solvent,
∆Hv and ∆Hf are the enthalpies of vaporization and fusion, respectively, of the solvent per gram,
c is the solute concentration (gr/cm3),
Mn is the number-average molecular weight.
A2 is a constant.
Formula Used
14
15. An example of determining Mn from vapour pressure data
15
16. Light Scattering
This method is presumed most popular for the determination of weight average molecular weight (Mw). It
allows polymer molecular weight and structure to be assessed. Fundamentally, if light passes through a
medium, it scatters at different angles. This technique thus relies on the measurement of light scattered at an
angle to the incident ray as it passes through the target. The intensity of scattered light incident on polymer
sample is dependent of the polarity, chain size, and concentration. Consequent upon this, light technique
measures polymer molecular weight by quantifying the Raleigh scattering (elastic light scattering) from each
polymer molecule. The measurement approach is simple as illustrated in the Figure below.
16
17. where ∆R𝜃 is the change in Raleigh scattering at a specified angle, K is the optical constant, C is the polymer
concentration, and is the average particle scattering factor which accounts for the effects of measuring
scattering from large molecules with relatively small wavelength.
LIMITATIONS:
However, the light scattering technique is deemed time consuming because it requires that the sample
solution is completely free of dust and other impurities as these are capable of influencing the light
scattering pattern. Also, as could be deduced from the above equation, change in Raleigh scattering is
proportional to the sample concentration and molecular weight, hence this method requires high sample
concentration to produce a detectable signal.
17
The scattered light and the average molecular weight is related according to the following equation:
The famousness of this method stems from the fact that wide range of molecular weight (typically
104 to 6 X 105 g/mol) can be determined.
18. It is the most intricate of the methods for determining the molecular-weights of high polymers. This
method is useful for biological materials, such as protein molecules.
An ultracentrifuge consists of an AL rotor (ø ∼1-2 inch) that is rotated at high speed in an evacuated
chamber. The solution being centrifuged is held in a small cell within the rotor near its periphery. The rotor
is driven electrically or by oil or air turbine.
The concentration of polymer is determined by optical methods based on measurements of refractive
index or absorption. The solvents must have difference both density and refractive index from the polymer.
The density differences allow the sedimentation and the refractive index differences allow the
measurement.
Ultracentrifugation (Sedimentation) Method
In the sedimentation equilibrium experiment, the ultracentrifuge is operated at a low speed of rotation for
times up 1 or 2 weeks under constant conditions. A thermodynamic equilibrium is reached in which the
polymer is distributed in the cell according to its molecular weight and molecular-weight distribution.
18
20. The force on a particle (F):
F = ω2r(1− υρ)m
where:
ω is the angular velocity of rotation,
r is the distance of the particle from the axis of rotation,
υ is the partial specific volume of the polymer,
ρ is the density of the solution,
m is the mass of the particle.
For an ideal solution in the equilibrium condition:
where: c1 and c2 are the concentrations at 2 points r1 and r2 in the cell.
LIMITATIONS: The disadvantage of sedimentation equilibrium experiment is taking quite long time to reach
equilibrium.
20
21. Ultracentrifugation Method
21
Example: At rotation rate 400 rpm (41.8 m/s) and 20 oC, the concentration ratio (C2/C1) is 1000. If the r2
and r1 are 5 cm and 10 cm , respectively, the density is 1 gm/cm3 and the partial specific volume of the
polymer is 0.0077 cm3/gm, what is the molecular weight.
SOLUTION:
Mw =
(2)(8.314)(293)ln(1000)
1 − 0.0077 ∗ 1 (41.8)2 ((0.1)2−(0.05)2)
Mw = 2587.8 𝑔𝑚/𝑚𝑜𝑙𝑒
22. Viscometry
A method that is widely use for routine molecular-weight determination is based on the
determination of intrinsic viscosity, η, of a polymer in solution through measurements of solution
viscosity.
The fundamental relationship between η and molecular-weight is given in Mark-Howink equation (mentioned
in Page 6):
22
It is clear in the above equation that the value of intrinsic viscosity of the diluted polymer is needed to
determine the molecular weight. To find the intrinsic viscosity, a series of experimental measurements and
calculations have to be made. These steps are as follows:
1. The relative viscosity can be measured experimentally using a suitable viscometer:
24. 24
Fig. 1 Reduced viscosity and inherent viscosity of nylon 66 in 90% formic acid (Adapted from Ph.D thesis of
R Walia, P. S., Chemical Engineering, West Virginia University, Morgantown, 1998).
Intrinsic Viscosity
26. One of the most widely used methods for routine determination of molecular weight and molecular-weight
distribution is GPC. This method based on the principle of size-exclusion chromatography to separate samples
of polydisperse polymers into fractions of narrower molecular-weight distribution.
The equipment:
Several small-diameter columns (L = 30 – 50 cm) are packed with small highly porous beads (∅ = 10 – 107 Â).
Pure pre-filtered solvent is continuously pumped through the columns at a constant flow rate
(1 – 2 mL/min). Then, a small amount (1 – 5 mL) of a dilute polymer solution is injected by syringe into the
solvent stream and carried through the columns. The smallest polymer molecules are able to penetrate deeply
into the bead pores but the largest may be completely excluded.
Gel Permeation Chromatography (GPC)
The process is repeated until all polymer molecules have been eluted out of the column in descending
order of molecular weight. The concentration of polymer molecules in each eluting fraction can be
monitored by means of a polymer-sensitive detector, such as IR or UV device. The detector is usually a
differential refractometer (differ the refractive index between the pure solvent and polymer solution).
For a given polymer, solvent, temperature, pumping rate, and column packing size, elution volume (Vr) is
related to molecular weight.
27.
28.
29. 29
Summary of the Measurements Method of M.wt
A = Absolute
E = Equivalent
R = Relative