Polymers Lec 1

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POLYMERSQasim HabibLecturerPolymer & Process Engineering DepartmentUET, Lahore4/26/2010Polymer & Process Engineering Department, UET, Lahore1Polymer Polymers are long chain giant organic molecules, assembled from repetitive bonding of many smaller molecules called monomers.Polymer is derived from two from Greek words poly (many) and meros (part)

4/26/2010Polymer & Process Engineering Department, UET, Lahore2IUPAC definition A polymer is a substance composed of molecules characterized by the multiple repetition of one or more species of atoms or groups of atoms (constitutional repeating units) linked to each other in amounts sufficient to provide a set of properties that do not vary markedly with the addition of one or a few of the constitutional repeating units.

4/26/2010Polymer & Process Engineering Department, UET, Lahore3History The term polymer was first used by Berzelius in 1827The concept of polymer as molecule with high molecular weight (at least few ten thousands) was introduced by the German Scientist Hermann Staudinger almost a century later (in 1920) which was at that time severely criticized.Baekeland in 1906 prepared the first synthetic polymer Bakelite.

4/26/2010Polymer & Process Engineering Department, UET, Lahore4 1833 : Berzelius, the first use of terminology, polymer 1839 : Synthesis of polystyrene 1860s : Poly(ethylene glycol), Poly(ethylene succinate) 1900s : Leo Baekeland, synthesis of phenol formaldehyde resin 1920s : Hermann staudinger: Structure of polymer (long-chain molecules), Novel Prize(1953) 1939 : W.H. Carothers, Nylon synthesis (Du Pont) 1963 : Ziegler-Natta, stereoregular polymerization 1974 : Paul Flory, polymer solution property 1984 : Bruce Merrifield, solid-phase protein process 4/26/2010Polymer & Process Engineering Department, UET, Lahore5StructureThe structure of a polymer related to the physical arrangement of monomers along the backbone of the chain.Structure has a strong influence on the other properties of a polymer. Polymer scientists have developed terminology to precisely describe both the nature of the monomers as well as their relative arrangement4/26/2010Polymer & Process Engineering Department, UET, Lahore6The polymer structure can be divided into 3 main classes.The chemical structure (atomic composition) of the monomer (primary structure)The structure of single polymer chain (secondary structure)Aggregation of polymer chains (tertiary structure)

4/26/2010Polymer & Process Engineering Department, UET, Lahore7Primary structurePrimary structure refers to the atomic composition and chemical structure of the monomer, the building block of the polymer chain. An appreciation of the nature of the monomer is fundamental to understanding the structureproperty relationship of polymers. The chemical and electrical properties of a polymer are directly related to the chemistry of the constituent monomers.

4/26/2010Polymer & Process Engineering Department, UET, Lahore8Factors determining the Primary structureThe nature of bonds in monomers (chemical bonding)The type of monomers that are capable of forming polymers (functionality of monomers)The mode of linking of monomers (polymerization mechanisms)The chemical composition of monomers and the properties conferred on monomers as a result of their chemical composition

4/26/2010Polymer & Process Engineering Department, UET, Lahore9Secondary structureSecondary structure is the size and shape of an isolated single molecule. The size of the polymer is best discussed in terms of molecular weight.The shape of the polymer molecule will be influenced naturally by the nature of the repeating unit and the manner in which these units are linked together.

4/26/2010Polymer & Process Engineering Department, UET, Lahore10ConfigurationArrangement fixed by primary valence bonds; can be altered only through the breaking or reforming of chemical bondsIf repeating units along the chain are chemically and sterically regular, then the polymer is said to possess structural regularity.

4/26/2010Polymer & Process Engineering Department, UET, Lahore11ConformationArrangement established by rotation about primary valence bondsChange in the overall shape and size of the polymer chain may occur due to rotation about primary valence bonds.A polymer molecule may assume a large or limited number of conformations depending on:Whether the polymer is amorphous or crystalline Whether the polymer is in a solution state, molten state, or solid state

4/26/2010Polymer & Process Engineering Department, UET, Lahore12Tertiary structureA given polymeric solid material is an aggregate of a large number of polymer molecules. Depending on the molecular structure, the process of molecular aggregation occurs essentially by either of two possible arrangements of molecules, leading to either a crystalline or amorphous material.

4/26/2010Polymer & Process Engineering Department, UET, Lahore13Classes of microstructureThere are two main classifications for the microstructures of polymers.Chemical structureGeometrical structure4/26/2010Polymer & Process Engineering Department, UET, Lahore14Microstructures based on Chemical structureOrganic & Inorganic polymersHomochain & Heterochain polymersHomopolymers & Copolymers 4/26/2010Polymer & Process Engineering Department, UET, Lahore15Organic & Inorganic polymersOrganic polymers: where the backbone is made essentially of Carbon-Carbon (C-C) links.e.g. Polyethylene , Polypropylene

Inorganic polymers: where backbone chain is of any other inorganic element like Silicon or Germanium. e.g. Polygerman.4/26/2010Polymer & Process Engineering Department, UET, Lahore16

Homochain & Heterochain polymersHomochain polymers: where the backbone chain is made entirely of a single type of atoms. e.g. Polyethylene, PolypropyleneHeterochain polymers: where the backbone have different types of atoms. E.g. polyethylene Adipate.4/26/2010Polymer & Process Engineering Department, UET, Lahore17

Homopolymers & Copolymers Homopolymers: where the entire polymer chain is made of one single repeat unit. e.g. PVC, PE, PP etcCopolymers: where the polymer is comprised of more than one type of repeat units. Two or more Homopolymers can join to give copolymer. e.g. polyvinyl chloride acetate monomer. Poly( vinyl chloride monomer + vinyl acetate monomer)4/26/2010Polymer & Process Engineering Department, UET, Lahore18Microstructures based on Geometrical structureLinear , Branched, Network & Cross linked polymersRandom, Alternating, Block & Graft polymersStereo Regular polymers4/26/2010Polymer & Process Engineering Department, UET, Lahore19Linear, Branched, Cross linked & Network PolymersLinear PolymerThe simplest form of polymer molecule is a straight chain or linear polymer, composed of a single main chain.

4/26/2010Polymer & Process Engineering Department, UET, Lahore20

Branched polymersSide branch chains are attached to the main chain which interferes with the relative movement of the molecular chains. This results in an increase in strength, deformation resistance and stress cracking resistance.


cross-linked polymersThree dimensional structure, adjacent chains are linked by covalent bonds. Polymers with cross-linked chains are called thermosetting plastics (thermosets), epoxy and Silicones.Cross-linking is responsible for providing hardness, strength, brittleness and better dimensional stability.


Network PolymersA three dimensional network of three or more covalent bonds. Thermoplastic polymers that have been already formed could be cross-linked to obtain higher strength. Polymers are exposed to high-energy radiation.


Random, Alternating, Block & Graft PolymersRandom copolymers: two monomers randomly distributed in chain.AABAAABBABAABBApoly(acrylonitrile-ran-butadiene)

Alternating copolymers: two monomers incorporated sequentiallyABABABABABABABABpoly(styrene-alt-maleic anhydride)

4/26/2010Polymer & Process Engineering Department, UET, Lahore24Block copolymers: linear arrangement of blocks of high mol weightAAAAAAAAAAABBBBBBBBBBBBBBBAAAAAAAApolystyrene-block-polybutadiene-block-polystyrene or poly(styrene-b-butadiene-b-styrene)

Graft copolymers: differing backbone and side-chain monomerspoly(isobutylene-graft-butadiene)

4/26/2010Polymer & Process Engineering Department, UET, Lahore25Stereo Regular polymersIn stereo regular polymers, each monomer segment is in a regular configuration, giving structural regularity to the polymerThere are two types of isomerismOptical or stereo IsomerismGeometric Isomerism4/26/2010Polymer & Process Engineering Department, UET, Lahore26Stereo IsomerismThere are three phenomena's related to stereoisomerism Isotactic SyndiotacticAtactic

4/26/2010Polymer & Process Engineering Department, UET, Lahore27Isotactic PolymersIn isotactic macromolecules all the substituents are located on the same side of the macromolecular backbone.


Syndiotactic PolymersIn syndiotactic or syntactic macromolecules the substituents have alternate positions along the chain.


Atactic Polymers In atactic macromolecules the substituents are placed randomly along the chain. Polymers that are formed by free-radical mechanisms such as polyvinylchloride are usually atactic.


Geometric IsomerismCis Isomerism: when the attached radicals are on the same side of the polymer.

Trans Isomerism: when the attached radical are on the opposite sides of the main chain.


4/26/2010Polymer & Process Engineering Department, UET, Lahore32Classification of PolymersThe classification is based on several considerations. The source of polymers Type of polymerization process Nature and type of chain Solid state behavior of polymer chains etc.4/26/2010Polymer & Process Engineering Department, UET, Lahore33

4/26/2010Polymer & Process Engineering Department, UET, Lahore34By occurrenceThe common natural polymers include polysaccharides (starch, cellulose, gums etc), proteins (gelatin, albumin, enzymes, insulin), polyisoprenes (natural rubber, gutta percha) and nucleic acids (RNA and DNA). Natural polymers are sometimes also called Biopolymers' or Biological macromolecules'.Synthetic polymers include polyethylene, olypropylene, poly methylmethacrylate, polystyrene, polyester, epoxy resins, Nylon..

4/26/2010Polymer & Process Engineering Department, UET, Lahore35By chemical compositions

4/26/2010Polymer & Process Engineering Department, UET, Lahore36By Chain structure

4/26/2010Polymer & Process Engineering Department, UET, Lahore37By processing propertiesThermosetting polymers: insoluble and only swell. Cross-linked polymers cannot be made to flow or melt irreversibly (network polymer)

Thermoplastic polymers: not crosslinked, soluble, will melt and flow. Most linear polymers take on new shapes by the application of heat and pressure (linear or branched polymer)


4/26/2010Polymer & Process Engineering Department, UET, Lahore39By physical or mechanical properties, or end usePolymers can also be classified further as fibers, plastics, resins and rubbersBased on the nature and extent of secondary valence forces and mobility among constitutional repeat units.

4/26/2010Polymer & Process Engineering Department, UET, Lahore40Organic polymers have chains consisting of C-C linkagesElemento-organic(or hetero organic)po1ymers include Macromolecules Inorganic chains in which side groups contain carbon atoms directly linked to chainInorganic polymers are polymers containing no carbon atoms

4/26/2010Polymer & Process Engineering Department, UET, Lahore41Polymers may be charged or uncharged. e.g. polyacrylic acid (anionic polymer) or polyethylene imine (cationic polymer). Charged polymers that are soluble in water are called as "polyelectrolytes".

4/26/2010Polymer & Process Engineering Department, UET, Lahore42Polymers may also be classified as amorphous or crystalline depending upon their morphological behaviour.These two types of polymers behave differently as crystallinity influences the properties such as hardness, stiffness and elasticity, thus making them useful as plastic, rubber, fiber or resin.

4/26/2010Polymer & Process Engineering Department, UET, Lahore43Monodispersed & Polydispersed PolymersMonodispersed Polymers: A polymers whose constituents have consistent and uniform mass & mass distribution are known as monodispersed.Anionic polymerization yields the mono dispersed polymers.Polydispersed Polymers: The polymers which have broad range of size and inconsistent mass distribution, are termed as Polydispersed polymers.4/26/2010Polymer & Process Engineering Department, UET, Lahore44NomenclatureA standard nomenclature system based on chemical structure as is used for small inorganic and organic compounds is most desired.Unfortunately, the naming of polymers has not proceeded in a systematic manner until relatively late in the development of polymer science.It is not at all unusual of a polymer to have several names because of the use of different nomenclature systems.4/26/2010Polymer & Process Engineering Department, UET, Lahore45The nomenclature systems that have been used are based on either the structure of the polymer or the source of the polymer [i.e., the monomer (s) used in its synthesis] or trade names.An important step toward standardization was initiated in the 1970s by the International Union of Pure and Applied Chemistry.This system is applicable primarily to polymers synthesized from a single monomer as in addition and ring-opening polymerizations.

4/26/2010Polymer & Process Engineering Department, UET, Lahore46Such polymers are named by adding the name of the monomer onto the prefix poly without a space or hyphen. Thus the polymers from ethylene and acetaldehyde are named polyethylene and polyacetaldehyde, respectively.When the monomer has a substituted parent name or a multi worded name or an abnormally long name, parentheses are placed around its name following the prefix poly. The polymers from 3-methyl-1-pentene, vinyl chloride, propylene oxide, chlorotrifluoroethylene, and E-caprolactam are named poly(3-methyl-1-pentene), poly(vinyl chloride), poly(propylene oxide), poly(chlorotrifluoroethylene), and poly(E-caprolactam), respectively.4/26/2010Polymer & Process Engineering Department, UET, Lahore47Types of Nomenclature: a. Source name : to be based on names of corresponding monomer Polyethylene, Poly(vinyl chloride), Poly(ethylene oxide) b. IUPAC name : to be based on systematic name Poly(1-chloroethylene), Poly(1-butene-1,4-diyl), c. Functional group name : According to name of functionalgroup in the polymer backbone Polyamide, Polyester d. Trade name : The commercial names by manufacturer Teflon, Nylon e. Abbreviation name : PVC, PET


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Polymers Lec 1