P O L Y M E R C H E M I S T R Y 1 . 1 · PDF filep o l y m e r c h e m i s t r y 1 . 1 n unit i polymer chemistry 1.1 introduction

P O L Y M E R C H E M I S T R Y 1 . 1

n

UNIT I

POLYMER CHEMISTRY

1.1 INTRODUCTION

The word polymer is derived from two Greek words. “Poly” means “many”

and “mers” means “parts” or “units”.

Polymers are generally macromolecules formed by the combination of a large

number of small molecules. Polymers are finding many applications in industrial areas

like automobile, defense, electrical and electronic goods and computer components,

etc.,

1.1.1 Polymers

Polymers are macromolecules which are formed by repeated linkage of large

number of small molecules called monomers.

For example, polyethylene is a polymer formed by the repeated linkage of large

number of ethylene molecules which are the monomers.

nCH2

== CH2 ––(– CH

2 –– CH

2–)––

Ethylene polyethylene

(monomer) (polymer)

1.1.2 Monomer

Monomer is a micromolecule which combines with other molecules of same

or different type to form a polymer chain.

Engineering Chemistry-I gineering Chemistry-I eering Chemistry-I ing Chemistry-I Chemistry-I emistry-I istry-I y-I 1.2

Engineering Chemistry-I 1.2

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Example :

Monomer Repeating unit of the polymer

CH2

= CH2

–– CH2 –– CH

2 ––

ethylene polyethylene

CH2

= CH –– CH2 –– CH ––

| |

CH3

CH3

propylene polypropylene

CH2

= CH –– CH2 –– CH ––

| |

Cl Cl

Vinyl chloride polyvinyl chloride

NH2 ––(

CH2 –)– NH

2

Hexamethylene diamine O

||

+ –– NH –(– CH2 –)– NH –– C ––( CH

2 –)– C ––

6

HOOC –(– CH –)– COOH nylon 6:6

4 || O

adipic acid

1.2 POLYMERISATION

The chemical process leads to the formation of polymer with or without

elimination of small molecule is known as polymerization.

nCH2

== CH

polymerization –(– CH

2 –– CH –)–

| | n

Cl Cl Vinyl chloride Poly vinyl chloride

1.2.1 Degree of polymerization

The number of repeating unit or monomers in a polymer chain is known as

degree of polymerization. It is denoted as “n”.


n Molecular weight of a polymer

Molecular weight of a monomer

Based on degree of polymerization, polymers can be classified into two types.

(i) Oligo polymers

(ii) High polymers

(i) Oligo polymers

Polymers with low degree of polymerization.

Molecular weight ranges from 500-5000.

(ii) High polymers

Polymers with high degree of polymerization.

Molecular weight ranges from 10000-200000

1.3 NOMENCLATURE OF POLYMERS

(i) Homopolymers

Polymers consists of identical monomers are known as homopolymers.

Example: PE, PVC, etc.,

– – –– M–M–M–M–M–M — – –

(ii) Heteropolymers

Polymers consists of different monomers are known as copolymers or

heteropolymers.

Example: Nylon, Buna –S-rubber,etc.,

– – –– M1–M

2–M

1–M

2–M

1–M

2–M

1— – –

(iii) Homochain polymer

If the main chain of a polymer is made up of the same type of atoms, the

polymer is called “homochain polymer”.

Engineering Chemistry-I

Example: PE, PVC, etc.,

– – – –– C–C–C–C–C–C–C–C –– – – –

(iv) Heterochain polymer

If the main chain of a polymer is made up of the different type of atoms, the

polymer is called heterochain polymer.

Example: Terylene, Nylon 6:6, Buna-S-rubber,etc.,

– – –– C–C–O–C–C–O–C–C–O–C–C–O –– – –

(v) Random copolymer

The polymers are arranged in random manner.

– – –– M1–M

2–M

2–M

1––M

1–M

1–M

2–M

1–M

1–M

2–M

2 –– – –

(vi) Block copolymer

The monomers are arranged as blocks. It is a linear polymer.

–– M1–M

2–M

1–M

1––M

2–M

2–M

1–M

1–M

2–M

2 ––

(vii) Graft copolymers

One type of monomer is the main chain and another type of monomer is the

side chain is called graft copolymer.

1.4 FUNCTIONALITY

The number of bonding or reactive sites present in a monomer is known as

its functionality.

Functionality Examples

Monomers having only one bonding

or reactive sites are called mono

functional monomers. They cannot CH3COOH, CH

3OH, RX, etc.

undergo polymerization. They can be

used as chain terminators.


Functionality Examples

Monomers having double bonds or

two reactive sites are called

bi-functional monomers. They will

form linear polymers.

CH

2=CH

2, HOOC–(CH

2)

4–

COOH, H2N–(CH

2)

6–NH

2, etc.

Monomers having the three reactive

sites are called tri-functional

monomers. They can form cross

linked polymers.

CH2 –– COOH CH

2 –– OH

| | CH – COOH CH OH | |

CH – COOH , CH OH 2 2

1.5 TYPES OF POLYMERIZATION

1.5.1 Addition (or) Chain growth polymerization

It is a reaction that yields a product, which is an exact multiple of the original

monomeric molecule. Such a monomeric molecule, usually contains one or more

double bonds.

The addition polymerisation reaction must be initiated by the application of heat,

light, pressure or a catalyst. They will form linear chain molecule.

In addition polymerization, other by products like water, ammonia or ethanol

are not formed.

Example 1: Formation of polyethylene

Heat / Pr essure n... –– CH

–– CH

–– ... nCH2 == CH2

catalyst 2 2

Bifunctional monomer

... ––( CH2 –– CH2 –)–n ....

Polyethylene (PE)

1.6 Engineering Chemistry-I

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Example 2: Formation of polyvinyl chloride

Heat / Pr essure n... –– CH

–– CH –– ... nCH2

== CH |

Cl

catalyst 2 | Cl

vinyl chloride Bifunctional monomer

... –(– CH2 –– CH –)– ....

| n

Cl

Polyvinyl chloride (PVC)

1.5.2 Condensation (or) Step-wise polymerization

It is a reaction occurs between simple polar groups containing monomers with

the formation of polymer and elimination of small molecules like water, HCl, etc.

Example : Formation of Nylon 6 : 6

H H O O

N CH2 N n 6

C CH2 C

H H HO OH

Hexamethylene Diamine Adipic acid

Polymerization

O O H H

N CH2 N 6

C CH2 C n

2nH2O

Nylon 6 : 6


n

2 n

Another type of condensation reaction

In some cases condensation occurs with ring opening but without elimination

of small molecules like H2O, HCl etc.

Example: Formation of Nylon 6

CH2 CH2

O H

CH2 CH2 CH N C 5

CH2 NH

CO

Caprolactam

Nylon - 6

1.5.3 Copolymerization

It is the joint polymerization in which two or more different monomers combine

to give a polymer. High molecular weight compounds obtained by copolymerization

are called copolymers.

Example:

nCH2

== CH –– CH == CH2

+ n CH2

== CH

Butadiene Styrene

Copolymerization

–(– CH2 –– CH == CH – CH

2–– CH

2–– CH –)–

Polybutadiene-co-Styrene

(Styrene-butadiene rubber, SBR)


1.5.4 Differences between Addition (Chain growth)

polymerization and Condensation (Step wise)

polymerization

S.No. Addition/chain growth

polymerization

Condensation / Step wise

polymerization

1 Monomers must have atleast

one multiple bond.

Monomers must have atleast two

reactive functional groups.

2 High molecular mass polymer is

formed at once.

Polymer molecular mass rises

steadily throughout the reaction.

3 Homochain polymers are

obtained.

Heterochain polymers are obtained.

4 Thermo plastic are produced. Thermo setting plastic are produced.

5 Linear chain polymers are

obtained.

Cross-linked polymers are obtained.

6 Monomers just add to give a

polymer and no other

by-products are formed.

Monomers combine to give a

polymer and by-products are

formed.

7 Longer reaction times give

higher yield, but have a little

effect on molecular weight.

To obtain high molecular weight,

longer reaction time is essential

8 Number of units decreases

steadily throughout the reaction.

Monomer disappears early in the

reaction.

9 Example: PE, PVC, etc. Example: Bakelite, Silicones, etc.

1.6 MECHANISM OF ADDITION POLYMERISATION

The mechanism of addition polymerization can be explained by any one of the

following three methods.

(i) Free radical mechanism

(ii) Ionic mechanism

(iii) Co-ordination mechanism


•

1.6.1 FREE RADICAL MECHANISM

This mechanism occur in three major steps namely,

(i) Initiation

(ii) Propagation

(iii) Termination

(i) Initiation

It is considered to involve two reactions.

(a) First reaction involves production of free radicals by homolytic dissociation

of an initiator or catalyst to yield a pair of free radicals (R•)

I 2R

Examples:

Initiator free radicals

Some commonly used thermal initiators

(i) CH3COO –– OOCCH

3

7090

o C 2CH3COO

(or) 2R

free radicals

8095o C

(ii) C6H

5COO –– OOCC

6H

5 2C6H5COO (or) 2R

(b) Second reaction involves addition of this free radical to the first monomer

to produce chain initiating species.

H H

R CH2 C R CH2 C

Y

First monomer

(ii) Propagation

Y

Chain initiating species


2

It consists of the growth of chain initiating species by successive additions of

large number of monomer molecules.

H

R CH2 C

Y

H

nCH2 C

Y

R CH2

H H

C CH C

n

Y Y

Growing Chain

(living polymer)

The growing chain of the polymer is known as living polymer.

(iii) Termination

The growing chain of polymer is terminated by either

(a) Coupling

(b) Disproportionation

(a) Coupling

It involves coupling of free radical of one chain end to another free radical

forming a macromolecule.

H

R CH2 C

H

C CH2 R

H R CH2 C

H

C CH2 R

Y Y Y Y

Macromolecule

(Dead polymer)

(b) Disproportionation

P O L Y M E R C H E M I S T R Y 1 . 1 1

It involves transfer of a hydrogen atom from one reactive chain end to another

t o fo r m mac r o mo lecu les. I n whic h, o ne is sa t ur a t ed and ano t her is

unsaturated.

H H H H H H

R C C + C C R R C C

H Y Y H

Y Unsaturated macromolecule

+ H H

H C C R

Y H

Saturated macromolecule

The product of the polymer is called dead p(oDlyemaedr.polymers)

1.6.2 IONIC MECHANISM

Ionic polymerisation takes place because of the charge separation in monomer

units. This is caused by the presence of substituents capable of either donating or

withdrawing electrons. The nature of substituents decides the path of polymerisation

reaction, either cationic or anionic.

(a) Cationic Mechanism

Presence of electron donating substituents favours the formation of cation-

intermediate in the polymerisation reaction They reduce the instability at carbonium

ion or carbocation centre, i.e., they stabilise the intermediate formed. Electron donating

or releasing groups are methyl, ethyl, etc.

(i) Initiation

Initiator or catalyst used are Lewis acids like AlCl3, BF

3, SnCl

4, TiCl

4, etc.

in presence of water (Co-catalyst).

H O + –

Example: AlCl3 2 H AlCl

3OH


3 3

3

3

3

H+AlCl OH–

+

H CH3

| | C = C | |

H CH3

H

| H – C –

| H

+ AlCl OH–

Chain Initiating species

(ii) Propagation

H CH3

+

H H

– | | H – C – C AlCl

3OH + n C – C

H CH3

| |

H CH3

H CH3

| | H CH

3

|

H C – C n C – C+ AlCl OH

–

| | H CH

3

| H CH

3

(iii) Termination

H

|

CH3

|

Chain growing

H CH

3

|

H C – C n C – C+

AlCl OH–

| | H CH

3

| H CH

3

Leaves as H+

H CH3

| | H CH

3

| |

H C – C n C – C + H+ AlCl OH–

| | H CH

3

| CH

3


3 K –

(b) Anionic mechanism

Presence of electron withdrawing substituents favours the formation of anion-

intermediate in the polymerisation reaction. They reduce the instability at carbanion

centre, i.e., they stabilise the intermediate formed. Electron withdrawing groups are

– Cl, –CN, –COOH, –C6H

5 etc.

(i) Initiation

Initiator or catalyst used are bases like LiNH2, KNH

2, n-butyl lithium etc. in

presence of liquid NH3.

Example :

KNH2

NH +

+ NH2

H H H H | | | |

NH–

+ C = C

NH – C – C

– 2 2

| | H CN

| H CN

(ii) Propagation

Chain Initiating species

H H H H H H H H

NH2 – C – C + n C – C NH2 C – C

n C – C –

| H CN

| | H CN

| |

H CN

| H CN

Chain growing

(iii) Termination

H H H H | | | |

H H H H | | | |

NH C – C C – C

– + HNH

NH C – C

C – C –H + NH

– 2 2 2 2

| |

H CN n

|

H CN | | | |

H CN n H CN


H H H H H H | | | | | |

C – C – C – C – C – C | | | | | |

H H H H H H

H H Cl H H H

| | | | | | C – C – C – C – C – C | | | | | |

Cl H H H Cl H

1.7 PROPERTIES OF POLYMERS

(i) Tg

The temperature at which the polymer experiences the transition from

rubbery to rigid states is termed the glass transition temperature (Tg).

The glass transition occurs in amorphous polymers, when upon cooling

from the liquid, crystallisation does not take place. i.e., the polymer chains are

unable to rearrange into a three dimensional, long-range ordered structure. Upon

cooling, the glass transition corresponds to an increase in viscosity and the

gradual transformation from a liquid to a rubbery materials and finally to a rigid

solid.

(ii) Tacticity

The orientation of monomeric units in a polymer molecule can take place

in an orderly or disorderly fashion with respect to the main chain is known as

tacticity.

There are three types.

(a) Isotactic : The monomeric functional groups are arranged in the same

side with respect to the main chain.

– –

(b) Syndiotactic : The monomeric functional groups are arranged in

alternative manner with respect to the main chain.

– –


H H H H Cl H Cl H

| | | | | | | |

M

i i

(c) Atactic : The monomeric functional groups are arranged in

random manner.

– C – C – C – C – C – C – C – C – | | | | | | | |

Cl H Cl H H H H H

(iii) Molecular weight - Weight average

Weight average molecular weight

relation.

(M w ) can be defined by the following

Ni M2

Ci Mi w

Ci

CiMi

c i Ni M

i

Where, Ci

= Weight concentration of Mi

molecules

c = total concentration of all polymer molecules.

(iv) Number average molecular weight

The number average molecular weight ( M n ) is defined as the total mass (w)

of all the molecules of polymer divided by the total number of molecules present.

Thus,

w N M Mn

Where,

N Ni

Ni Number of molecules of mass M

i.

M n can be determined by measuring the colligative properties like lowering

of vapour pressure, depression of freezing point etc.

(v) Polydispersity index

The weight average molecular mass is always greater than the number average

as the ratio molecular mass. So the ratio of

Mw / Mn

may be used as a measure

of the molecular mass distribution or an index of polydispersity.


The ratio of the weight-average molecular weight (Mw ) to that of number-

average molecular weight

(M n ) is known as polydispersity index (PDI).

1.8 TECHNIQUES OF POLYMERISATION

1.8.1 Bulk polymerisation

Polymerisation of the pure liquid or gaseous monomer is called bulk

polymerisation. It can be used for the production of free radical polymers and some

condensation polymers.

In the reaction only monomer, polymer and initiator are present and therefore

a very pure product is obtained.

The polymerisation is very rapid and strongly exothermic. It can lead to

hazardous temperature build up and run away reactions. Overheating can cause

branching and crosslinking and lead to the formation of gels.

The process produces highly transparent polymers. Example: PS

1.8.2 Solution polymerisation

The monomer is added to an inert solvent with a boiling point that corresponds

to the polymerisation temperature.

During the polymerisation process some solvent evaporates and thus helps

to remove the heat of polymerisation.

Since the boiling point of the solvent is constant, this ensures a constant

polymerisation temperature.

Some difficulty lies in the separation of the residual solvent from the polymer

after completion of polymerisation.

In comparison with bulk polymerisation, solution polymerisation offers easier

temperature control because of the added heat ca pacity of solvent and

lower viscosity.


1.8.3 Suspension polymerisation

Suspension polymerisation is essentially a bulk polymerisation carried

out in droplets in an aqueous solution in which the monomer is

dispersed. The polymer precipitates as fine spherical particles with

diameters of 0.01 to 1.0 nm.

The polymerisation begins by radical initiators in the monomer droplets.

The water absorbs the heat of reaction.

Residual additives need to be removed.

1.8.4 Emulsion polymerisation

Monomer

droplet

Polymerisation

Micelle Micelle with growing polymer chain

Initiation

Surfactant molecule consist of a hydrophilic and hydrophobic part (head & tail)

Head (Polar)

tail (non polar)

Sodium dodecylsulface C12

H25

OSO3Na

O S - +

O O Na

Fig. 1.1 Emulsion polymerisation


It is limited to addition polymerisation. The basic principle is to finely

disperse the water insoluble monomer in water. The dispersion of the monomer

takes place in the presence of surfactant that form micelles.

Water soluble initiator enters the micelle and polymerisation starts. The

monomer consumed in the micellers is replaced by diffusion from the monomer

droplets through the aqueous phase, by this method high molecular weight

polymer is obtained at faster polymerisation rate.

Since each polymerisation sites are isolated. The continuous water phase is an

excellent conductor of heat which removes the heat from system. The dispersion

resulting from emulsion polymerisation is called a latex.

Advantage of this method is that it has better heat control, the size of the

emulsion polymer is usually 0.05 to 5 microns.

1.9 CLASSIFICATION OF POLYMER

Based on origin polymers can be classified as into two types:

(i) Natural (ii) Synthetic

(i) Natural polymer: The polymer obtained from natural source are called

natural polymers.

Examples: Proteins, silk, wool, carbohydrate, DNA.

(ii) Synthetic polymer: It is man-made polymers. Polymer synthesized from

low molecular weight compound called synthetic polymer.

Examples: Polyethylene, polyvinyl chloride, polystyrene.

1.10 CLASSIFICATION OF PLASTICS

Plastics are classified in the following two ways.

(i) Based on structure

(ii) Based on usage

1.10.1 Classification based on structure

Based on the structure and type of resin used for the manufacture of plastics,

plastics are classified into two main types.


(a) Thermoplastics

(b) Thermosetting plastics

Resin

A resin is a basic binding material, which form a part of the plastics, it

undergoes polymerization and condensation reactions during moulding.

(a) Thermoplastic resins

Thermoplastics are prepared by addition polymerization. They can be softened

on heating and hardened on cooling. They are soft and less brittle.

They are generally linear polymers. A weak Vander Waals force is present

between the two adjacent layers. They are soluble in organic solvents.

Examples: PE, PVC, PP, PS, nylons, Teflon, etc.,

– M. – M – M – M – M. –

. . – M – M – M – M.

.

– M –

. . – M – M – M – M – M –

(b) Thermosetting resins (or) Thermosets

Thermosetting plastics are prepared by condensation polymerization.

– M – M – M – M – M –

– M – M – M – M – M –

– M – M – M – M – M –

They are interconnected by strong covalent bonds. They are rigid, strong

and brittle. They got hardened and gain strength on heating. If once set, it

cannot be softened again. They are not soluble in organic solvents. They cannot be

recycled.

Examples : Polyester, Bakelite, epoxy-resin, urea-formaldehyde, etc.


The following table 1.1 gives the difference between thermoplastics and

thermosetting plastics.

Table 1.1 The difference between thermoplastics and thermosetting plastics

S.No. Thermoplastic resins Thermosetting resins

1 They are formed by addition

polymerization.

They are formed by condensation

polymerization

2 They are linear in structure. They are cross linked polymers.

3 These can be reclaimed from

wastes.

They cannot be reclaimed from

wastes.

4 Weak Vander Waals force is

present.

Strong covalent bonds are

present.

5 They are usually soft, weak

and less brittle.

They are usually hard, strong

and more brittle.

6 They soften on heating and

harden on cooling.

They do not soften on heating.

7 They have low molecular weight. They have high molecular weight.

8 They are soluble in organic

solvents.

They are insoluble in organic

solvents.

9 By reheating to a suitable

temperature, they can be reused,

reshaped and thus reused.

They retain their shape and structure,

even on heating. Hence, they cannot

be reshaped and reused.

1.10.2 Classification based on usage

Based on usage plastics are classified into two types.

(i) General purpose plastics

(ii) Engineering plastics

(i) General purpose plastics

General purpose plastics are used for the manufacture of commodity items.

They have low mechanical properties.


They have poor dimensional stability.

Examples : PE, PP, PVC

Properties

They have low abrasion resistance.

They are mostly amorphous polymers.

They have low to medium mechanical properties.

1.11 ENGINEERING PLASTICS

Engineering plastics or performance plastics are a group of materials obtained

from high polymer resins. They possess high toughness and mechanical strength. They

possess higher use temperature. The economy and ease of fabrication have now

made them engineering materials of construction. Not only engineering plastics can

replace metals, but they can also be used along with metals.

1.11.1 Charact]eristics (or) Properties of engineering plastics

Engineering plastics possess

High mechanical strength

High abrasion resistance

Good dimensional stability

High dielectric constants

Fairly good thermal stability

High load-bearing characteristics

Plasticity at some stage of their processing

Readily mouldable characteristics into complicated shapes

Rigidity

Light weight

High performance properties, which permit them to be used in the

same manner as metals, alloys and ceramics.


1.11.2 Applications

They are finding applications in demanding areas like automobiles,

defence, elect r ical and elect r o nics, t ext iles, sat e llit e, r o bo t s,

telecommunications, mountaineering, computer components, etc.

They can be used alone or in conjunction with metals, glasses or

ceramics, etc.

1.12 IMPORTANT ENGINEERING PLASTICS

1.12.1 Nylon (Polyamides)

(i) Nylon-6:6

It is obtained by the polymerization of adipic acid with hexamethylene diamine.

H H O O

n N CH2 6 N n C CH2

4 C

H H HO OH

Hexamethylene Diamine Adipic acid

Polymerization

O O H H

N CH2 N 6

C CH2 C 4

n

2nH2O

(ii) Nylon 6 Nylon 6 : 6

It is prepared by self-polymerization of caprolactam.

CH2

CH2 H O

CH2 CH2 CH2 N C 5 n

CH2 NH

CO Caprolactam

Nylon - 6


(iii) Nylon-11

It is obtained by self-condensation of -amino undecanoic acid.

H

n N ( CH2 )10 C

OH Self - condensation

polymerisation

N ( CH2

)10 C

H O H O n

Properties

They are translucent, whitest, horny and high melting (160 to 264oC)

polymers.

They are insoluble in common organic solvents and soluble in phenol and

formic acid.

They possess high temperature stability.

They possess good abrasion-resistance.

Uses

Nylon-6:6 is mainly used for fibres, which is used in making socks, dresses,

carpets, etc.,

Nylon-6 and Nylon-11 are mainly used for moulding purposes for gears,

bearings, electrical mountings, etc.,

They are used for making filaments for ropes, films, bristles for tooth-

brushes, etc.,

1.12.2 Epoxide (or) Epoxy Resins

Preparation

Epoxy resins are important cross-linked thermosetting resins. They are

polyethers, because R–O–R type is present in the structure. The value of n ranges

from 1 to 20.

Epoxy resins are prepared by the condensation of epichlorohydrin with

bisphenol-A.


n CH2 – CH – CH2 – Cl + nHO

O

CH3

C OH

CH3

Aq. NaOH

– CH2 – CH – CH2 O

OH

CH3

C

CH3

O + nHCl

n

Properties

They have tough.

They have good heat resisting property.

They are flexible.

They have good adhesion property due to the presence of polar nature.

They have good chemical resistance to alkalis, acids, solvents and water

etc., due to the presence of stable other linkage.

Uses

They are employed for the production of components for aircrafts and

automobiles.

They are applied over cotton, rayon and bleached fabrics to impart crease

resistance and shrinkage control.

They are used as laminating materials, used in electrical equipments.

Epoxy resin adhesives are sold in the market as in the name of “Araldite”.

They are used for skid - resistant surfaces for highways.


ANNA UNIVERSITY QUESTIONS

AND EXPECTED QUESTIONS

1. Explain the mechanism of fr ee r adical addit io n polymer izat io n.

[Chen. A.U. Jan. 2010]

2. Distinguish thermoplastics and thermosetting plastics with suitable examples.

[TNV. AU. Jan. 2010]

3. Explain the term functionality of a monomer. Give its significance.

[CBE. AU. May. 2011]

4. Write the mechanism of free radical polymerization. [CBE.AU. May. 2011]

5. What is meant by degree of polymerization? [CBE. AU. July. 2010]

6. Differ ent iat e be t ween addit io n and co ndensat io n po lymer iz at io n.

[CBE. AU. July. 2010]

7. Define the term functionality. [CBE. AU. Feb. 2010]

8. Distinguish between addition and condensation polymerization

[CBE. AU. Feb. 2010]

9. What is co-polymerization. Give examples. [AU, Dec.2002]

10. Explain the mechanism of cationic polymerization with an example.

11. Explain the mechanism of anionic polymerization with an example.

12. Mention the properties and uses of epoxy resin.

13. Write the synthesis, properties and uses of nylon -6:6.


14. Explain bulk, emulsion, solution and suspension polymerization techniques.

15. Write short notes on Tg, weight average molecular weight, tacticity and

polydispersity index.

16. Explain condensation polymerization with an example.

17. Explain addition polymerization with an example.

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P O L Y M E R C H E M I S T R Y 1 . 1 · PDF filep o l y m e r c h e m i s t r y 1 . 1 n unit i polymer chemistry 1.1 introduction