Dr. Sonia Rani presented on polymers. She defined key terms like monomers, polymers and polymerization. Polymers are classified based on their source (natural, semi-synthetic, synthetic), structure (linear, branched, cross-linked) and molecular forces. The two main types of polymerization reactions are addition/chain growth and condensation/step growth. Important addition polymers like polythene, polypropylene and nylon were discussed along with their preparations. Copolymerization and natural rubber were also summarized.
Polymer chemistry involves the study of polymers, which are large molecules composed of many repeating structural units connected by covalent bonds. The monomers that make up polymers are linked through polymerization reactions. Polymers can be classified based on their structure, source, number of monomers, arrangement of monomers, and configuration. Common types of polymers include linear, branched, and cross-linked polymers. Polymers are also classified as natural, semi-synthetic, or synthetic based on their source. Polymerization reactions are either addition polymerization, involving chain growth, or condensation polymerization, involving step growth. Important conducting polymers include intrinsically conducting polymers and extrinsically conducting polymers. Biopolymers include nucleic acids, proteins,
Polymer chemistry involves the study of polymers, which are large molecules composed of many repeating structural units connected by covalent bonds. The monomers that make up polymers are linked through polymerization reactions. Polymers can be classified based on their structure, source, number of monomers, arrangement of monomers, and configuration. Common types of polymers include linear, branched, and cross-linked polymers. Polymers are also classified as natural, semi-synthetic, or synthetic based on their source. Polymerization reactions are either addition polymerization, involving chain growth, or condensation polymerization, involving step growth. Polymers have a variety of applications and properties depending on their structure and bonding forces.
Polymers are giant molecules composed of repeating structural units joined together. They can be classified based on their origin (natural, semi-synthetic, synthetic), thermal response (thermoplastic, thermosetting), structure (linear, branched, cross-linked), and application (rubber, plastic, fibers). Polymerization is the process of linking monomers together to form polymers. It occurs via two main mechanisms: step-growth polymerization (condensation polymerization) and chain-growth polymerization (addition polymerization). Step-growth involves the elimination of a small molecule as monomers react together in a step-wise manner, while chain-growth is a chain reaction with no byproducts as monomers continuously add to the
Dental polymers with recent advancements in dental base techniques 2PoojaKhandelwal45
This document discusses recent advancements in dental polymers and base techniques. It begins with definitions of polymers and polymerization. The history of dental polymers is then reviewed, including the development of synthetic elastomers in the 20th century and the introduction of PMMA and resin-based composites. Various dental applications of polymers are listed. Key aspects of polymers like chain length, branching, copolymer structures, and properties are described. The document concludes with an overview of addition and step-growth polymerization, as well as details on acrylic dental resins.
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.
Polymers are giant molecules formed from many repeating units or monomers. They can be either homopolymers made of one monomer type, or copolymers made of two or more different monomers. Polymers are classified based on their structure, molecular forces, and mechanism of polymerization. Thermoplastics can be remelted and remolded, while thermosets harden irreversibly. Important polymers include polyethylene, polyester, nylon, PVC, and Teflon. They find wide use in products like bottles, fibers, pipes, coatings and more.
Polymers are macro molecules formed by linking smaller molecules called monomers repeatedly. Polymers can be classified in several ways, including by origin (natural vs synthetic), structure (linear, branched, cross-linked), method of formation (addition vs condensation), response to heat (thermosetting vs thermoplastic), and properties/applications (plastics, elastomers, fibers, resins). Key properties of polymers like tensile strength, plastic deformation, chemical resistance, and crystallinity depend on factors like intermolecular forces, molecular shape and arrangement, and chemical composition.
Polymer chemistry involves the study of polymers, which are large molecules composed of many repeating structural units connected by covalent bonds. The monomers that make up polymers are linked through polymerization reactions. Polymers can be classified based on their structure, source, number of monomers, arrangement of monomers, and configuration. Common types of polymers include linear, branched, and cross-linked polymers. Polymers are also classified as natural, semi-synthetic, or synthetic based on their source. Polymerization reactions are either addition polymerization, involving chain growth, or condensation polymerization, involving step growth. Important conducting polymers include intrinsically conducting polymers and extrinsically conducting polymers. Biopolymers include nucleic acids, proteins,
Polymer chemistry involves the study of polymers, which are large molecules composed of many repeating structural units connected by covalent bonds. The monomers that make up polymers are linked through polymerization reactions. Polymers can be classified based on their structure, source, number of monomers, arrangement of monomers, and configuration. Common types of polymers include linear, branched, and cross-linked polymers. Polymers are also classified as natural, semi-synthetic, or synthetic based on their source. Polymerization reactions are either addition polymerization, involving chain growth, or condensation polymerization, involving step growth. Polymers have a variety of applications and properties depending on their structure and bonding forces.
Polymers are giant molecules composed of repeating structural units joined together. They can be classified based on their origin (natural, semi-synthetic, synthetic), thermal response (thermoplastic, thermosetting), structure (linear, branched, cross-linked), and application (rubber, plastic, fibers). Polymerization is the process of linking monomers together to form polymers. It occurs via two main mechanisms: step-growth polymerization (condensation polymerization) and chain-growth polymerization (addition polymerization). Step-growth involves the elimination of a small molecule as monomers react together in a step-wise manner, while chain-growth is a chain reaction with no byproducts as monomers continuously add to the
Dental polymers with recent advancements in dental base techniques 2PoojaKhandelwal45
This document discusses recent advancements in dental polymers and base techniques. It begins with definitions of polymers and polymerization. The history of dental polymers is then reviewed, including the development of synthetic elastomers in the 20th century and the introduction of PMMA and resin-based composites. Various dental applications of polymers are listed. Key aspects of polymers like chain length, branching, copolymer structures, and properties are described. The document concludes with an overview of addition and step-growth polymerization, as well as details on acrylic dental resins.
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.
Polymers are giant molecules formed from many repeating units or monomers. They can be either homopolymers made of one monomer type, or copolymers made of two or more different monomers. Polymers are classified based on their structure, molecular forces, and mechanism of polymerization. Thermoplastics can be remelted and remolded, while thermosets harden irreversibly. Important polymers include polyethylene, polyester, nylon, PVC, and Teflon. They find wide use in products like bottles, fibers, pipes, coatings and more.
Polymers are macro molecules formed by linking smaller molecules called monomers repeatedly. Polymers can be classified in several ways, including by origin (natural vs synthetic), structure (linear, branched, cross-linked), method of formation (addition vs condensation), response to heat (thermosetting vs thermoplastic), and properties/applications (plastics, elastomers, fibers, resins). Key properties of polymers like tensile strength, plastic deformation, chemical resistance, and crystallinity depend on factors like intermolecular forces, molecular shape and arrangement, and chemical composition.
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.
Polymers play a very important role in human life. Our body is made of lot of polymers, e.g. Proteins, enzymes, etc. Other naturally occurring polymers like wood, rubber, leather and silk are have wide application. Now a day synthetic polymer like useful plastics, rubbers and fiber materials are synthesized. presentation includes introduction classification and preparation methods. Polymers play a very important role in human life. Our body is made of lot of polymers, e.g. Proteins, enzymes, etc. Other naturally occurring polymers like wood, rubber, leather and silk are have wide application. Now a day synthetic polymer like useful plastics, rubbers and fiber materials are synthesized. Leo Baekeland patented the first totally synthetic polymer called Bakelite (1910). Bakelite is a versatile, durable material prepared from low-cost materials phenol and formaldehyde and was the most important synthetic polymer material. In the 1920s Hermann Staudinger showed that polymers were high-molecular-weight compounds held together by normal covalent bonds.
The suffix in polymer ‘mer’ is originated from Greek word meros – which means part. The word polymer is thus coined to mean material consisting of many parts or mers. A macromolecule having high molecular mass (103-107u) and generally not a well-defined structure or molecular weight. The macromolecules formed by joining of repeating structural units on a large scale. The repeating structural units are simple and reactive molecules linked to each other by covalent bonds. This process of formation of polymers from respective monomers is called polymerization. Most of the polymers are basically organic compounds, however they can be inorganic (e.g. silicones based on Si-O network).
This document summarizes different types of polymers. It discusses the classification of polymers based on source, structure, mode of polymerization, molecular forces, and provides examples. Key polymers discussed include polyethylene, polyvinyl chloride, nylon, bakelite, phenol-formaldehyde, and melamine-formaldehyde. The document also explains the processes of addition, condensation, and step-growth polymerization.
Polymers are large molecules composed of repeating structural units called monomers. They can be either natural or synthetic. Approximately 80% of the organic chemical industry is devoted to producing synthetic polymers. Polymers are classified as addition or condensation polymers depending on the chemical reaction involved in linking the monomers. Examples of important synthetic polymers include polyethylene, polyvinyl chloride, nylon, polyester, Teflon, and Kevlar. Substituted groups attached to the polymer chain determine properties like reactivity and strength. Crosslinking polymer chains increases strength through covalent bonds between chains.
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 discusses polymers, including their classification, types, properties, and applications. Polymers are high molecular mass substances composed of repeating structural units joined by covalent bonds. They can be classified as homopolymers or copolymers depending on the number of monomer units. Polymers are also classified by their polymerization reaction as addition or condensation polymers. Examples of common polymers are discussed. The properties of polymers depend on factors like chain length and branching, which influence strength. Polymers have a wide range of applications, from packaging and clothing to industrial uses like pipes and tanks to sports equipment and medical uses like surgical materials.
Polymers are long chains of repeating molecular units called monomers. There are several types of polymers including polyethene, polypropene, nylons, polyurethanes, and polyesters. Polymers are classified based on their structure and production method. Properties depend on factors like chain length and structure. Common applications include plastic containers, clothing, pipes, sports equipment, and medical devices.
Polymers are long chains of repeating molecular units called monomers. There are several types of polymers including polyethene, polypropene, nylons, polyurethanes, and polyesters. Polymers are classified based on their structure and production method. Properties depend on factors like chain length and structure. Common applications include plastic containers, clothing, pipes, sports equipment, and medical devices.
The document discusses various topics related to polymers including their classification, types, mechanisms of polymerization, and polymerization reactions. It classifies polymers based on their chain structure, chemical composition, source, and backbone. The main types discussed are thermoplastics, thermosets, and elastomers. It describes the mechanisms of condensation and addition polymerization. Chain polymerization reactions like free radical, anionic and cationic polymerization are explained in detail with their initiation, propagation and termination steps.
This document provides an overview of polymers, including:
- Polymers are large molecules made by linking repeating units called monomers. Naturally occurring polymers have been used for thousands of years, while artificial polymers were developed more recently after WWII.
- Polymers can be classified based on their source, thermal behavior, chemical structure, stereochemistry, and end use. Important types include thermoplastics, thermosets, homopolymers, copolymers, fibers, and plastics.
- Polymer properties depend on factors like strength, crystallinity, elasticity, and glass transition temperature which are influenced by the polymer structure. Common characterization techniques and molding processes like injection molding are also discussed.
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 various topics related to polymers including their classification, types, mechanisms of polymerization, and methods of polymerization. Polymers can be classified based on their chain structure, chemical composition, source, and backbone. The main types are thermoplastics, thermosets, and elastomers. Polymerization can occur via addition or condensation reactions and methods include bulk, solution, suspension, and emulsion polymerization.
Methods of polymerisation It is also called as Zeigler – Natta polymerisation.
Zeigler (1953) and Natta (1955) discovered that in the presence of a combination of transition metal halides like TCl4, ZnBr3 etc, with an organometallic compound like triethyl-aluminium or trimethyl-aluminium, stereospecific polymerisation can be carried out.
Combination of metal halides and organometallic compounds are called Zeigler Natta catalyst.
This document provides information about polymers and polymerization. It defines a polymer as a long molecule formed by joining thousands of small monomer units through chemical bonds. The degree of polymerization refers to the number of repeating monomer units in the polymer chain. Polymers can be classified based on their source, structure, tacticity, monomer units, end uses, conductance, environmental impact, and behavior when heated. The two main types of polymerization are addition polymerization and condensation polymerization. Examples of daily use polymers like polyethylene, polyvinyl chloride, nylon, bakelite etc. are also discussed along with their properties and applications.
This document summarizes various ways of classifying polymers. Polymers can be classified based on their structure as linear, branched, or cross-linked. They can also be classified based on their source as natural, semi-synthetic, or synthetic. Additionally, polymers are classified based on the number and arrangement of monomers, their configuration, the intermolecular forces between chains, and the type of polymerization reaction (addition or condensation). The document provides examples for most polymer classifications.
Polymerization is the process of converting small molecule monomers into long chains or networks of polymers. There are two main types of polymerization: step-growth and chain-growth. Step-growth polymers form through the stepwise reaction of functional groups on monomers, slowly increasing molecular weight over time. Chain-growth polymerization involves monomers linking together through carbon-carbon double or triple bonds, forming polymers like polyethylene and polyvinyl chloride through free radical or ionic mechanisms. Polymerization is used industrially to produce many common plastics and requires control of initiation, propagation and termination to achieve high molecular weight polymers.
Polymerization is the process of converting small molecule monomers into long chains or networks of polymers. There are two main types of polymerization: step-growth and chain-growth. Step-growth polymers form through the stepwise reaction of functional groups on monomers, slowly increasing molecular weight over time. Chain-growth polymerization involves monomers linking together through carbon-carbon double or triple bonds, forming polymers like polyethylene and polyvinyl chloride through free radical or ionic mechanisms. Photopolymerization is a type of chain-growth polymerization initiated by light absorption.
This document provides an overview of polymers including their classification, methods of polymerization, important natural and synthetic polymers, and commercial applications. It discusses:
1. Classification of polymers as natural, semi-synthetic, or synthetic based on their source and structure as linear, branched, or cross-linked.
2. The two main polymerization methods - addition (chain growth) and condensation (step growth) - and examples of each including polyvinyl chloride, nylon, polyester, phenol-formaldehyde, and rubbers.
3. Important natural polymers like natural rubber and its vulcanization, as well as synthetic versions like neoprene.
4. Commercial polymers are classified
Polymers have played an integral role in advancing drug delivery technology by providing remote control of drug release. Polymers can conjugate to therapeutics to improve their pharmacokinetic and pharmacodynamic properties through increased plasma half-life, protection from enzymes, reduced immunogenicity, and potential for targeted delivery. Polymers are composed of repeating monomer units connected by covalent bonds and can be classified based on their monomer composition, method of polymerization, architecture, application, morphology, and degradability. Common polymers used in drug delivery systems include PEG, PLGA, chitosan, and HPMC.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
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.
Polymers play a very important role in human life. Our body is made of lot of polymers, e.g. Proteins, enzymes, etc. Other naturally occurring polymers like wood, rubber, leather and silk are have wide application. Now a day synthetic polymer like useful plastics, rubbers and fiber materials are synthesized. presentation includes introduction classification and preparation methods. Polymers play a very important role in human life. Our body is made of lot of polymers, e.g. Proteins, enzymes, etc. Other naturally occurring polymers like wood, rubber, leather and silk are have wide application. Now a day synthetic polymer like useful plastics, rubbers and fiber materials are synthesized. Leo Baekeland patented the first totally synthetic polymer called Bakelite (1910). Bakelite is a versatile, durable material prepared from low-cost materials phenol and formaldehyde and was the most important synthetic polymer material. In the 1920s Hermann Staudinger showed that polymers were high-molecular-weight compounds held together by normal covalent bonds.
The suffix in polymer ‘mer’ is originated from Greek word meros – which means part. The word polymer is thus coined to mean material consisting of many parts or mers. A macromolecule having high molecular mass (103-107u) and generally not a well-defined structure or molecular weight. The macromolecules formed by joining of repeating structural units on a large scale. The repeating structural units are simple and reactive molecules linked to each other by covalent bonds. This process of formation of polymers from respective monomers is called polymerization. Most of the polymers are basically organic compounds, however they can be inorganic (e.g. silicones based on Si-O network).
This document summarizes different types of polymers. It discusses the classification of polymers based on source, structure, mode of polymerization, molecular forces, and provides examples. Key polymers discussed include polyethylene, polyvinyl chloride, nylon, bakelite, phenol-formaldehyde, and melamine-formaldehyde. The document also explains the processes of addition, condensation, and step-growth polymerization.
Polymers are large molecules composed of repeating structural units called monomers. They can be either natural or synthetic. Approximately 80% of the organic chemical industry is devoted to producing synthetic polymers. Polymers are classified as addition or condensation polymers depending on the chemical reaction involved in linking the monomers. Examples of important synthetic polymers include polyethylene, polyvinyl chloride, nylon, polyester, Teflon, and Kevlar. Substituted groups attached to the polymer chain determine properties like reactivity and strength. Crosslinking polymer chains increases strength through covalent bonds between chains.
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 discusses polymers, including their classification, types, properties, and applications. Polymers are high molecular mass substances composed of repeating structural units joined by covalent bonds. They can be classified as homopolymers or copolymers depending on the number of monomer units. Polymers are also classified by their polymerization reaction as addition or condensation polymers. Examples of common polymers are discussed. The properties of polymers depend on factors like chain length and branching, which influence strength. Polymers have a wide range of applications, from packaging and clothing to industrial uses like pipes and tanks to sports equipment and medical uses like surgical materials.
Polymers are long chains of repeating molecular units called monomers. There are several types of polymers including polyethene, polypropene, nylons, polyurethanes, and polyesters. Polymers are classified based on their structure and production method. Properties depend on factors like chain length and structure. Common applications include plastic containers, clothing, pipes, sports equipment, and medical devices.
Polymers are long chains of repeating molecular units called monomers. There are several types of polymers including polyethene, polypropene, nylons, polyurethanes, and polyesters. Polymers are classified based on their structure and production method. Properties depend on factors like chain length and structure. Common applications include plastic containers, clothing, pipes, sports equipment, and medical devices.
The document discusses various topics related to polymers including their classification, types, mechanisms of polymerization, and polymerization reactions. It classifies polymers based on their chain structure, chemical composition, source, and backbone. The main types discussed are thermoplastics, thermosets, and elastomers. It describes the mechanisms of condensation and addition polymerization. Chain polymerization reactions like free radical, anionic and cationic polymerization are explained in detail with their initiation, propagation and termination steps.
This document provides an overview of polymers, including:
- Polymers are large molecules made by linking repeating units called monomers. Naturally occurring polymers have been used for thousands of years, while artificial polymers were developed more recently after WWII.
- Polymers can be classified based on their source, thermal behavior, chemical structure, stereochemistry, and end use. Important types include thermoplastics, thermosets, homopolymers, copolymers, fibers, and plastics.
- Polymer properties depend on factors like strength, crystallinity, elasticity, and glass transition temperature which are influenced by the polymer structure. Common characterization techniques and molding processes like injection molding are also discussed.
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 various topics related to polymers including their classification, types, mechanisms of polymerization, and methods of polymerization. Polymers can be classified based on their chain structure, chemical composition, source, and backbone. The main types are thermoplastics, thermosets, and elastomers. Polymerization can occur via addition or condensation reactions and methods include bulk, solution, suspension, and emulsion polymerization.
Methods of polymerisation It is also called as Zeigler – Natta polymerisation.
Zeigler (1953) and Natta (1955) discovered that in the presence of a combination of transition metal halides like TCl4, ZnBr3 etc, with an organometallic compound like triethyl-aluminium or trimethyl-aluminium, stereospecific polymerisation can be carried out.
Combination of metal halides and organometallic compounds are called Zeigler Natta catalyst.
This document provides information about polymers and polymerization. It defines a polymer as a long molecule formed by joining thousands of small monomer units through chemical bonds. The degree of polymerization refers to the number of repeating monomer units in the polymer chain. Polymers can be classified based on their source, structure, tacticity, monomer units, end uses, conductance, environmental impact, and behavior when heated. The two main types of polymerization are addition polymerization and condensation polymerization. Examples of daily use polymers like polyethylene, polyvinyl chloride, nylon, bakelite etc. are also discussed along with their properties and applications.
This document summarizes various ways of classifying polymers. Polymers can be classified based on their structure as linear, branched, or cross-linked. They can also be classified based on their source as natural, semi-synthetic, or synthetic. Additionally, polymers are classified based on the number and arrangement of monomers, their configuration, the intermolecular forces between chains, and the type of polymerization reaction (addition or condensation). The document provides examples for most polymer classifications.
Polymerization is the process of converting small molecule monomers into long chains or networks of polymers. There are two main types of polymerization: step-growth and chain-growth. Step-growth polymers form through the stepwise reaction of functional groups on monomers, slowly increasing molecular weight over time. Chain-growth polymerization involves monomers linking together through carbon-carbon double or triple bonds, forming polymers like polyethylene and polyvinyl chloride through free radical or ionic mechanisms. Polymerization is used industrially to produce many common plastics and requires control of initiation, propagation and termination to achieve high molecular weight polymers.
Polymerization is the process of converting small molecule monomers into long chains or networks of polymers. There are two main types of polymerization: step-growth and chain-growth. Step-growth polymers form through the stepwise reaction of functional groups on monomers, slowly increasing molecular weight over time. Chain-growth polymerization involves monomers linking together through carbon-carbon double or triple bonds, forming polymers like polyethylene and polyvinyl chloride through free radical or ionic mechanisms. Photopolymerization is a type of chain-growth polymerization initiated by light absorption.
This document provides an overview of polymers including their classification, methods of polymerization, important natural and synthetic polymers, and commercial applications. It discusses:
1. Classification of polymers as natural, semi-synthetic, or synthetic based on their source and structure as linear, branched, or cross-linked.
2. The two main polymerization methods - addition (chain growth) and condensation (step growth) - and examples of each including polyvinyl chloride, nylon, polyester, phenol-formaldehyde, and rubbers.
3. Important natural polymers like natural rubber and its vulcanization, as well as synthetic versions like neoprene.
4. Commercial polymers are classified
Polymers have played an integral role in advancing drug delivery technology by providing remote control of drug release. Polymers can conjugate to therapeutics to improve their pharmacokinetic and pharmacodynamic properties through increased plasma half-life, protection from enzymes, reduced immunogenicity, and potential for targeted delivery. Polymers are composed of repeating monomer units connected by covalent bonds and can be classified based on their monomer composition, method of polymerization, architecture, application, morphology, and degradability. Common polymers used in drug delivery systems include PEG, PLGA, chitosan, and HPMC.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
Travis Hills of MN is Making Clean Water Accessible to All Through High Flux ...Travis Hills MN
By harnessing the power of High Flux Vacuum Membrane Distillation, Travis Hills from MN envisions a future where clean and safe drinking water is accessible to all, regardless of geographical location or economic status.
ESR spectroscopy in liquid food and beverages.pptxPRIYANKA PATEL
With increasing population, people need to rely on packaged food stuffs. Packaging of food materials requires the preservation of food. There are various methods for the treatment of food to preserve them and irradiation treatment of food is one of them. It is the most common and the most harmless method for the food preservation as it does not alter the necessary micronutrients of food materials. Although irradiated food doesn’t cause any harm to the human health but still the quality assessment of food is required to provide consumers with necessary information about the food. ESR spectroscopy is the most sophisticated way to investigate the quality of the food and the free radicals induced during the processing of the food. ESR spin trapping technique is useful for the detection of highly unstable radicals in the food. The antioxidant capability of liquid food and beverages in mainly performed by spin trapping technique.
PPT on Direct Seeded Rice presented at the three-day 'Training and Validation Workshop on Modules of Climate Smart Agriculture (CSA) Technologies in South Asia' workshop on April 22, 2024.
1. Presented by:
Dr. Sonia Rani
Assistant Professor
Department of Chemistry
Dayanand Girls P. G. College, Kanpur
Uttar Pradesh- 208001
POLYMER
2. Introduction
Define the terms: Monomers, Polymers & Polymerization
Classification of Polymers
Types of Polymerization Reactions
Preparation of Important Addition Reaction
Preparation of Important Addition Reaction
Co Polymerization
Rubber
Biodegradable Polymers
Content
3. Introduction
The word ‘polymer’ is coined from two Greek words: poly means many and mer means unit or part.
Plastics or polymers are integral part of our daily life.
Polymers have huge applications everywhere.
For example: - Hot water bag, tooth brush, switches, ropes etc.
are all made of polymers
Introduction of Polymer-
4. The term polymer is defined as a chemical substance of a very high molecular mass (103-107u) formed by combination
of a simple molecule, called monomers.
•Polymers are also known as macromolecules, which are formed by repeating structural units on large scale, these
monomers are linked by covalent bond.
•This process of formation of polymers from respective monomers is called polymerization.
•For example:-
Define the terms: Monomers, Polymers & Polymerization
5. 1. Natural polymers- These polymers are found in plants and animals. Examples are proteins, cellulose, starch,
some resins and rubber.
2. Semi-synthetic polymers
Cellulose derivatives as cellulose acetate (rayon) and cellulose nitrate, etc. are the some examples.
3. Synthetic Polymers
A variety of synthetic polymers as plastic (polythene), synthetic fibres.
Examples: - (nylon 6, 6) and synthetic rubbers (Buna - S) are polymers extensively used in
daily life as well as in industry.
Classification based on Source
6. Classification based on Structure of polymers
There are three different types based on the structure of the polymers.
Linear Polymers: - These polymers consist of long and straight chains. The examples are high density polythene,
polyvinyl chloride, etc. These are represented as:
Branched chain polymers:- These polymers contain linear chains having some branches, e.g. low density
polythene. These are depicted as follows:
Cross linked or Network polymers:- These are usually formed from bi-functional and tri-functional monomers
and contain strong covalent bonds between various linear polymer chains, e.g. Bakelite, melamine, etc. These
polymers are depicted as follows:
7. Addition polymers: -
The addition polymers are formed by the repeated addition of monomer molecules possessing double or triple bonds.
For example: - The formation of polythene from Ethene and polypropene from propene.
However, the addition polymers formed by the polymerisation of a single monomeric species are known as
homopolymers. For example: - polythene.
n CH2=CH2 (CH2-CH2)n Homopolymer
Ethene Polythene
The polymers made by addition polymerisation from two different monomers are termed as copolymers, e.g., Buna-
S, Buna-N, etc.
nCH2 = CH- CH =CH2 + nC6H5CH=CH2 (CH2-CH=CH-C6H5-CH2-CH-CH2)n
1,3 – Butadiene Styrene Butadiene-styrene copolymer
(Buna-S)
Classification on the basis of mode of polymerisation
8. 2.Condensation polymers
•The condensation polymers are formed by repeated condensation reaction between two different bi-functional or tri-
functional monomeric units.
• In these polymerisation reactions, the elimination of small molecules such as water, alcohol, hydrogen chloride, etc.
take place.
• The examples are Terylene (Dacron), nylon 6, 6, nylon 6, etc.
• For example, nylon 6, 6 is formed by the condensation of hexamethylene diamine with adipic acid.
hexamethylene diamine adipic acid. nylon 6, 6,
Classification on the basis of mode of polymerisation (Cont.)
9. A large number of polymers can be used in different fields because of their mechanical properties like tensile strength,
elasticity, toughness etc.
These mechanical properties are governed by intermolecular forces, e.g., van der Waals forces and hydrogen bonds,
present in the polymer. These forces also bind the polymer chains.
The polymers are classified into the following four sub groups on the basis of magnitude of intermolecular forces
present in them.
1) Elastomers: -
These are rubber – like solids with elastic properties.
The polymer chains are held together by the weakest intermolecular forces. These weak binding forces permit the
polymer to be stretched.
A few ‘crosslinks’ are introduced in between the chains, which help the polymer to retract to its original position after
the force is released as in vulcanised rubber. The examples are Buna-S, Buna-N, neoprene, etc.
Classification based on Molecular forces
10. 2) Fibres:- Fibres are the thread forming solids which possess high tensile strength and high modulus.
These characteristics can be attributed to the strong intermolecular forces like hydrogen bonding.
These strong forces also lead to close packing of chains and thus impart crystalline nature. The examples are
polyamides (nylon 6, 6), polyesters (terylene), etc.
3) Thermoplastic Polymers:- These are the linear or slightly branched long chain molecules capable of repeatedly
softening on heating and hardening on cooling.
These polymers possess intermolecular forces of attraction intermediate between elastomers and fibres.
Some common thermoplastics are polythene, polystyrene, polyvinyl, etc.
Classification based on Molecular forces (Cont.)
11. 4) Thermosetting Polymers:-
These polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in
moulds and again become infusible.
These cannot be reused. Some common examples are Bakelite, urea-formaldehyde resins, etc.
Classification based on Molecular forces (Cont.)
12. Types of Polymerization Reactions
There are broadly 2 types of polymerization reactions:-
1. Addition or chain growth polymerization
2. Condensation or step growth polymerization
1. Addition or chain growth polymerization
The molecules of the same monomer or different monomers add together on a large scale to form a polymer.
The monomers used are unsaturated compounds, e.g., alkenes, alkadienes and their derivatives.
This mode of polymerisation leading to an increase in chain length or chain growth can take place through the
formation of either free radicals or ionic species.
However, the free radical governed addition or chain growth polymerisation is the most common mode.
Contd.
Types of Polymerization Reactions
13. Types of Polymerization Reactions
There are broadly 2 types of polymerization reactions:-
1. Addition or chain growth polymerization
2. Condensation or step growth polymerization
1. Addition or chain growth polymerization
The molecules of the same monomer or different monomers add together on a large scale to form a polymer.
The monomers used are unsaturated compounds, e.g., alkenes, alkadienes and their derivatives.
This mode of polymerisation leading to an increase in chain length or chain growth can take place through the
formation of either free radicals or ionic species.
However, the free radical governed addition or chain growth polymerisation is the most common mode.
Contd.
Types of Polymerization Reactions
14. 1.1 Free Radical Mechanism:-
Many of alkenes or dienes and their derivatives are polymerized in the presence of a free radical (catalyst) like
benzoyl peroxide.
The sequence of steps may be depicted as follows:
Chain initiation steps
Chain propagating step
Chain terminating step
For example:- The polymerisation of Ethene to polythene consists of heating or exposing to light a mixture of Ethene
with a small amount of benzoyl peroxide initiator.
Chain initiating step-The process starts with the addition of phenyl free radical formed by the peroxide to the Ethene
double bond thus generating a new and larger free radical. This step is called chain initiating step.
1. Addition or chain growth polymerization (Free Radical Mechanism)
15. Chain propagating step - As this radical reacts with another molecule of Ethene, another bigger sized radical is
formed. The repetition of this sequence with new and bigger radicals carries the reaction forward and the step is
termed as chain propagating step.
Ultimately, at some stage the product radical thus formed reacts with another radical to form the polymerised product.
This step is called the chain terminating step.
Addition or chain growth polymerization (Contd.)
16. Ionic polymertication is initiated by acid such as H2SO4, HF or BF3 in H2O. Following steps are involved:
1. Chain initiation: The acid catalyst gives proton.
2. Chain Propagation- The carbonium ion adds to another molecule of alkene to produce a new carbonium ion.
Which can similarly add to another molecule of alkene and so on.
3. Chain termination- The chain reaction can be halted by combination with an anion or by loss of a proton.
Addition or chain growth polymerization (Ionic Mechanism)
17. Ionic polymertication is initiated by acid such as H2SO4, HF or BF3 in H2O. Following steps are involved:
1. Chain initiation: The acid catalyst gives proton.
2. Chain Propagation- The carbonium ion adds to another molecule of alkene to produce a new carbonium ion.
Which can similarly add to another molecule of alkene and so on.
3. Chain termination- The chain reaction can be halted by combination with an anion or by loss of a proton.
Addition or chain growth polymerization (Ionic Mechanism)
18. Preparation of Important Addition Reaction
1. Polythene: - There are two types of polythene-
(i) Low density polythene:
It is obtained by the polymerisation of Ethene under high pressure of 1000 to 2000 atmospheres at a temperature of
350 K to 570 K in the presence of traces of dioxygen or a peroxide initiator (catalyst).
The low density polythene (LDP) obtained through the free radical addition and H-atom abstraction has highly
branched structure.
Low density polythene is chemically inert and tough but flexible and a poor conductor of electricity.
Hence, it is used in the insulation of electricity carrying wires and manufacture of squeeze bottles, toys and flexible
pipes.
Preparation of Important Addition Reaction
19. (ii) High density polythene:
It is formed when addition polymerisation of Ethene takes place in a hydrocarbon solvent in the presence of a
catalyst such as triethylaluminium and titanium tetrachloride (Ziegler-Natta catalyst) at a temperature of 333 K to
343 K and under a pressure of 6-7 atmospheres.
High density polythene (HDP) thus produced, consists of linear molecules and has a high density due to close
packing.
It is also chemically inert and more tough and hard. It is used for manufacturing buckets, dustbins, bottles, pipes,
etc.
Preparation of Important Addition Reaction (Contd.)
20. 2. Polytetrafluroethene (Teflon)
Teflon is manufactured by heating tetrafluoroethene with a free radical or per sulphate catalyst at high pressures.
It is chemically inert and resistant to attack by corrosive reagents. It is used in making oil seals and gaskets and
also used for non – stick surface coated utensils.
Preparation of Important Addition Reaction (Contd.)
Preparation of tetrafluoroethene
21. 3. Polypropylene:- It is obtained by polymerization propylene. Polypropylene is used in the manufacture of
houseware (pans, drinking glass), medical equipment, toys, tubes etc.
4. Polyvinyl chloride:- It is obtained by polymerization vinyl chloride. Polyvinylchloride is used in the manufacture
of imitation leather, floor covering, roofing material and gramophones records.
Vinyl chloride is obtained from acetylene by treatment with HCL in the presence of HgCl2
Preparation of Important Addition Reaction (Contd.)
22. 5. Polyacrylonitrile
The addition polymerisation of acrylonitrile in presence of a peroxide catalyst leads to the formation of
polyacrylonitrile.
Polyacrylonitrile is used as a substitute for wool in making commercial fibres as Orlon or acrilan.
6. Polystyrene- It is obtained by polymerization of styrene. Polystyrene is used in the manufacture of food container,
cosmetic bottles, plastic cups, toys etc.
Preparation of Important Addition Reaction (Contd.)
23. Condensation Polymerization or step growth polymerization
•This type of polymerisation involves a repetitive condensation reaction between two bi-functional monomers.
•These poly condensation reactions results in the loss of some simple molecules as water, alcohol, etc., and lead to the
formation of high molecular mass condensation polymers.
•In these reactions, the product of each step is again a bi-functional species and the sequence of condensation goes on.
•Since, each step produces a distinct functionalised species and is independent of each other; this process is also
called as step growth polymerisation.
•The formation of Terylene or Dacron by the interaction of ethylene glycol and terephthalic acid is an example of this
type of polymerisation
2. Condensation Polymerization or step growth polymerization
24. Preparation of Important Addition Reaction
1. Polyamides:-These polymers possessing amide linkages are important examples of synthetic fibres and are termed
as nylons. The general method of preparation consists of the condensation polymerisation of diamines with
dicarboxylic acids and also of amino acids and their lactams.
Preparation of Nylons
Nylon 6, 6:- It is prepared by the condensation polymerisation of hexamethylenediamine with adipic acid under high
pressure and at high temperature. Nylon 6, 6 is used in making sheets, bristles for brushes and in textile industry.
Nylon 6:- It is obtained by heating Caprolactum with water at a high
temperature. Nylon 6 is used for the manufacture of tyre cords,
fabrics and ropes.
25. 2. Polyesters: - These are the poly condensation products of dicarboxylic acids and diols.
Dacron or Terylene is the best known example of polyesters. It is manufactured by heating a mixture of ethylene
glycol and terephthalic acid at 420 to 460 K in the presence of Zinc acetate antimony trioxide catalyst. Dacron fibre
(Terylene) is crease resistant and is used in blending with cotton and wool fibres and also as glass reinforcing
materials in safety helmets, etc.
3. Phenol – formaldehyde polymer (Bakelite and related polymers):-
Phenol - formaldehyde polymers are the oldest synthetic polymers.
These are obtained by the condensation reaction of phenol with formaldehyde in the presence of either an acid or a
base catalyst. The reaction starts with the initial formation of o-and/or p-hydroxymethylphenol derivatives, which
further react with phenol to form compounds having rings joined to each other through –CH2 group. The initial
product could be a linear product – Novolac used in paints.
26. Novolac on heating with formaldehyde undergoes cross linking to form
infusible solid mass called Bakelite. It is used for making combs,
phonograph records, electrical switches and handles of various utensils.
27. 4. Melamine- formaldehyde Polymer:-
Melamine formaldehyde polymer is formed by the condensation polymerisation of melamine and formaldehyde. It is
used in the manufacture of unbreakable crockery.
28. Copolymerisation is a polymerisation reaction in which a mixture of more than one monomeric species is allowed to
polymerise and form a copolymer. The copolymer can be made not only by chain growth polymerisation but by step
growth polymerisation also. It contains multiple units of each monomer used in the same polymeric chain.
For example:-a mixture of 1, 3 – butadiene and styrene can form a copolymer.
Copolymers have properties quite different from homopolymers.
For example: - butadiene - styrene copolymer is quite tough and is a good substitute for natural rubber.
It is used for the manufacture of auto tyres, floor tiles, footwear components, cable insulation, etc.
Co- Polymerization
29. Rubber
Rubber is a natural polymer and possesses elastic properties.
It is also termed as elastomer and has a variety of uses.
It is manufactured from rubber latex which is a colloidal dispersion of rubber in water. This latex is obtained from
the bark of rubber tree and is found in India, Sri Lanka, Indonesia, Malaysia and South America.
1. Natural Rubber
Natural rubber may be considered as a linear polymer of isoprene (2-methyl-1, 3-butadiene) and is also called as
cis - 1, 4 -polyisoprene.
The cis-polyisoprene molecule consists of various chains held together by weak van der Waals interactions and has
a coiled structure.
Thus, it can be stretched like a spring and exhibits elastic properties.
Natural Rubber
30. Vulcanization of Rubber:-
Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 K) and shows
high water absorption capacity.
It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. To improve upon these
physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw
rubber with sulphur and an appropriate additive at a temperature range 373 K to 415K.
On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.
In the manufacture of tyre rubber, 5% of sulphur is used as a crosslinking agent.
The probable structures of vulcanised rubber molecules are depicted below:
Natural Rubber
31. 2.Synthetic Rubber
•Synthetic rubber is any vulcanisable rubber like polymer, which is capable of getting stretched to twice its length.
•However, it returns to its original shape and size as soon as the external stretching force is released.
•Thus, synthetic rubbers are either homopolymers of 1, 3 - butadiene derivatives or copolymers of 1, 3 - butadiene or
its derivatives with another unsaturated monomer.
Preparation of Synthetic Rubbers
(i) Neoprene:-
•Neoprene or poly chloroprene is formed by the free radical polymerisation of chloroprene.
•It has superior resistance to vegetable and mineral oils.
•It is used for manufacturing conveyor belts, gaskets and hoses.
Synthetic Rubber
32. (ii) Buna –N:-
•Buna –N is obtained by the copolymerisation of 1, 3 – butadiene and acrylonitrile in the presence of a peroxide
catalyst.
•It is resistant to the action of petrol, lubricating oil and organic solvents. It is used in making oil seals, tank lining,
etc.
Synthetic Rubber
33. A large number of polymers are quite resistant to the environmental degradation processes and are thus responsible
for the accumulation of polymeric solid waste materials.
Aliphatic polyesters are one of the important classes of biodegradable polymers.
Some important examples are given below:
Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV)
It is obtained by the copolymerisation of 3-hydroxybutanoic acid and
3 - Hydroxypentanoic acid.
PHBV is used in speciality packaging, orthopaedic devices and in controlled release of drugs. PHBV undergoes
bacterial degradation in the environment.
Biodegradable Polymers
34. Symmetrical monomers such as ethylene and tetrafluoroethylene can join together in only one way. Monosubstituted
monomers, on the other hand, may join together in two organized ways, described in the following diagram, or in a
third random manner. Most monomers of this kind, including propylene, vinyl chloride, styrene, acrylonitrile and
acrylic esters, prefer to join in a head-to-tail fashion, with some randomness occurring from time to time. The reasons
for this regioselectivity will be discussed in the synthetic methods section.
Stereochemistry in Polymers
35. If the polymer chain is drawn in a zig-zag fashion, as shown above, each of the substituent groups (Z) will necessarily
be located above or below the plane defined by the carbon chain. The polymer has many chirality centre, raising the
possibility of millions stereoisomers. Consequently we can identify three configurational isomers of such polymers.
If all the substituents lie on one side of the chain the configuration is called isotactic.
If the substituents alternate from one side to another in a regular manner the configuration is termed syndiotactic.
If, a random arrangement of substituent groups is referred to as atactic.
Stereochemistry in Polymers (Contd.)