Polymer�Polymer: Maromolecule built-up by the linking together of a large no. of small molecules

Ex. Nucleic acid, paper, bakelite,PVC

�Monomer: The small molecule which combine with each other

� Mer: The repeat unit

�Degree of polymerisation (DP): The no. of repeating unit(n)Degree of polymerisation=Molecular wt of the polymeric network/molecular wt of the repeating unit

�Depends on degree of polymerisation polymers are two types

�Oligo polymers:Polymer with low mol.wt

�High ploymer: Polymer with high mol. wt

Polypropylene

mer

Monomer

Nomenclature of PolymerI. Based on the chemical structure of monomer

i)Homo polymer and ii)copolymer

II. Based on the arrangement of monomer in the structure

Homo Polymer:

i)Linear, ii)branched and iii)Cross linked or 3-D polymer

Co polymer:

Linear:i) Regular, ii)Alternating, iii) block and iv)random

copolymer

Branched: Graft copolymer

Cross-linked copolymer

III. Based on atoms in the main chain

i)Homochain polymer and ii)heterochain polymer

Nomenclature-contdI)Based on the chemical nature of the monomer units

� Homopolymer : Identical monomers Homopolymer : Identical monomers (Polyethylene)(Polyethylene)

� Copolymer : Monomers with different chemical Copolymer : Monomers with different chemical structure (Buna-S: butadiene and styrene)structure (Buna-S: butadiene and styrene)

II) Based on structure of polymer chains II) Based on structure of polymer chains (Homopolymer &Copolymer)(Homopolymer &Copolymer)

i. Linear homopolymer : - A – A – A – A – i. Linear homopolymer : - A – A – A – A – ii. Branched homopolymer : - A – A – A – A -

A

iii. Cross – linked polymer :

- A – A – A – A – A – A – A – A -

- A – A – A – A – A – A – A –

Linear polymer

Branched chain polymer

Cross linked or 3-D polymer-Bakelite

Copolymers� Regular Polymer : Regular

arrangement of monomer units A&B

� Alternating copolymers with regular alternating A and B units

� Random copolymers with random sequences of monomer A and B

� Block copolymers comprised of two or more homo polymer subunits in long sequences linked by covalent bonds

� Graft Copolymers are a special type of branched copolymer in which the side chains are structurally distinct from the main chain.

A-A-A-B-A-A-A-B-A-A-A-B

Regular Copolymer

Nomenclature-contd

III)III. Based on atoms in the main chain

� Homochain polymer: Main chain is made up of same species of atoms

Ex., PVC

� ii)heterochain polymer: Main chain is made up of different atoms

ex.,Nylon 6:6 (mer),

Copolymer ( Buna-S or SBR)

mer

Tacticity (Difference in Configuration)Affect their physical properties

Isotactic: Functional gpsor side

gps are all on the same

side:ex., Polypropylene

synthesised using Zielgar Natta

catalyst

Syndiotactic Arrangement of

functional groups or side gps in

alternating fashion: Gutta

percha-Natural rubber

Atactic: Arrangement of

functional gps or side gpsare

at random around the main

chain ex., Polypropylene

Functionality� Number of bonding sites in a monomer

� It determines the structure of the polymer.

Three Typee

� Bifunctional, trifunctional and polyfunctional1

1)Bifunctional monomer:Two reactive sites or bonding sites.

� Reactive gp attach side by side to each other forming linear or straight chain molecule

� Monomer units linked by covalent bonds but different chains are held by van der Waals force

� Chain movement in one direction is possible

� Compound with double bond, amino acid, di-ol etc.,

� ex., ethylene glycol, ethylene.

Functionality -contd

2)Trifunctional monomer: Contains three active sites

� Result in branched chain molecule even if it presents in small amount with bifunctional monomer ex.,dimethylol phenol

� Movement of chain molecules are restricted due to presence of side chain

3) Containing more than three functional gps.ex., trimetylol phenol

Monomers are connected to each other by covalent bonds which results in the formation of 3D network ex., bakelite

� The movement of individual molecules are prevented by strong cross-links

Types of Polymerisation• Addition or Chain polymerisation : Polymer is formed by an

addition reaction, where many monomers bond together via rearrangement of bonds without the loss of any atom or molecule

• Monomers contains one or more double bonds which by intermolecular rearrangement make the polymer which is an exact multiple of monomer

• Reaction is instigated by the application of heat, light, pressure or a catalyst -break the double bond.

• The polymerisation once initated cannot continue indefinitely as it becomes difficult to sustain long chain.

• Growth reaction adds repeating units one at a time to the chain

• Ex for Homo polymerisation ; PVC

Addition or Chain polymerisation • Ex. Homo polymerisation :,Nylon-6: Involves an intramolecular

rearrangement of bonds by opening of cyclic monomer

• Ex. Copolymerization of two different monomer:Polybutadiene-co-styrene

mer

Condensation or Step Polymerisation

• Reaction between simple polar gp containing monomers

• Formation of polymer takes place by elimination of small molecules like water, HCl, CH3OH, NH3 etc.,

• An intermolecular combination of monomer.

• When monomers contain three functional gps it may give cross-linked structure molecule.

• Ex.,(Nylon 6,6)

+ 2n H2O

n n

n

Chain and condensation polymerisation•Chain polymerisation

•Monomer must have two bonding

sites

•Inter molecular or intramolecular

Rearrangement

•Mostly results in homo chain

polymer

•Only growth reaction adds repeating

units one at a time to the chain

•Number of units decreases steadily

throughout the reaction

•Reaction mixture contains only

monomer and polymer- no other pdts

•Linear polymer and Thermoplastics

•Mol. Wt of polymer is exact multiple

of mol.wt of monomer

•longer reaction time has little effect

on the molecular wt but gives higher

yields

Condensation polymerisation

•Monomer must contain polar group

• Intermolecular combination of

monomers

•Mostly results in hetero chain polymer

•All types of molecular species present

can react

•Monomer disappears early in the

reaction

• All types of molecular species and by

products are present at any stage

•Branched and cross-linked polymer-

thermosetting plastics

•Molecular wt is not an exact multiple of

mol.wt of monomer

•Moecular mass (DP)rises steadily

throughout the reaction and hence

reaction time is essential

ClassificationClassification� Based on origin:Based on origin:

Natural (Cellulose, Protein, silicone) and synthetic Natural (Cellulose, Protein, silicone) and synthetic

(Bakelite)(Bakelite)

Based on Structure Based on Structure

Linear, Branched, 3-dimensional or cross linkedLinear, Branched, 3-dimensional or cross linked

Based on main chain (back bone/ skeleton)Based on main chain (back bone/ skeleton)

i) Homo chain: made up of single type of atom (ex) PEi) Homo chain: made up of single type of atom (ex) PE

ii) Hetero chain: made up of different types of atoms ii) Hetero chain: made up of different types of atoms

(ex)nylons(ex)nylons

Based on molecular forces (Thermal behaviour) Based on molecular forces (Thermal behaviour)

Thermoplastics, Thermosetting plastics, Fibres, ElastomersThermoplastics, Thermosetting plastics, Fibres, Elastomers

� Based on method of synthesis Based on method of synthesis

Addition polymer (eg) PE, PP, PS, nylon 6. Addition polymer (eg) PE, PP, PS, nylon 6.

Condensation polymer (eg)Polyesters , nylon 6,6 Condensation polymer (eg)Polyesters , nylon 6,6

Thermo plastics and Thermosetting plasticsThermo plastics and Thermosetting plasticsThermosetting Plastics�Do not soften; they burn on heating

�3-D cross-linked structure with co-valent bond

�Condensation polymer

�Can not be reshaped

�Hard, strong and brittle

�Cannot be reclaimed

�Due to strong bonds and cross links they are insoluble in almost all org. solvents Ex.,Bakelite

Thermo plastics�Soften on heating and harden on cooling reversibly

�Long-chain macromolecule

�Addition polymerisation

�Reshaped, reused

�Soft, weak and less brittle

�Reclaimed from waste

�Soluble in some org. solvents

�Ex., PVC

Elastomers and Fibers

Elastomer: Rubber

• High elastic properties

• Can be stretched to 4 to 10 times its original length

• Unstressed condition they are not in straigth chain but in the form of coil

Fibers

• Held by strong intermolecular forces like

H-bonding

• Continuous filament ex. Cellulose

Plastics

Org .materials of high mol.wt, which can be moulded

into any desired form, when subject to pressure and

heat in presence of the catalyst

Resin

� Basic binding material, a macro molecule (polymer),

major parts of the plastics

� Undergoes polymerization and condensation

�during preparation (Thermosetting plastics).

�Mixed with 4-10 ingredients-Compounding

�of plastics

• Classification Plastics

1) Based on usage

Commodity plastics

� PE, PS , PP, PVC,

Engineering Plastics

� Teflon (PTFE) ,PC (Lexan), Polyesters and

Polyamides (Nylon, PET)

2) Based on thermal behaviour

Thermoplsatics

Thermosetting plastics

Engineering PlasticsEngineering Plastics� Used to replace conventional materials like metal, wood, glass, Used to replace conventional materials like metal, wood, glass,

ceramics etc.ceramics etc.� Used to develop composite articlesUsed to develop composite articles

CharacteristicsCharacteristics� Resistant to corrosionResistant to corrosion� cast into any desired shapecast into any desired shape� light-weightlight-weight� low thermal coefficient of expansionlow thermal coefficient of expansion� chemical inertnesschemical inertness� low melt.pt.low melt.pt.� decorative finishdecorative finish� impermeable to waterimpermeable to water� low heat resistancelow heat resistance� deformation under load,deformation under load,� High abrasion resistanceHigh abrasion resistance� Dimensional stabilityDimensional stability

ApplicationsIn automobile

In defense

Electrical and electronics

Telecommunication

Textile

Satellite

Computer components (table top, screen)

Robots

In aeronautical engineering

Chemical industry

Paper Industry

Adhesives

Lubricants