POLYMERS

GIST

1.

Polymer:

It is a very large molecule having molecular mass 103 - 107 g mol-1. They are
formed by joining together repeating structural units.

2.
(a)

Classification of Polymers:

Based On Source:

(i)

Natural: Found in plants and animals, e.g. Proteins, cellulose, natural

rubber, silk, wool.

(ii)

Synthetic: Man-made e.g. Nylon, polyster, neoprene, Bakelite, Teflon,

PVC, polystyrene.

(b)
(i)

Based On Structure:

Linear Polymers: this consist of long and straight chain repeating

units e.g. Polythene (HDPE), PVC, nylon, polyester.

(ii)

Branched Polymers: This contain linear chains having some branches e.g.
amylopectin, glycogen etc.

(iii)

Cross Linked Polymers: Strong covalent bonds are present

between various linear polymer chains. E.g. Bakelite, urea- formaldehyde polymer,
melamine, formaldehyde polymer etc.
(c) Based On Mode Of Polymerization:

(i)

Addition Polymers: These are formed by the repeated addition of

monomer molecules possessing multiple bonds, e.g., polythene, polypropene,

polystyrene, PMMA (polymethylmethacrylate)

(ii)

Condensation Polymers: These are formed by the repeated

condensation reaction of different bifunctional or trifunctional monomers, with the

elimination of small molecules like water,HCL,NH3, alcohol etc. e.g.
Bakelite,nylon,polyster,urea- formaldehyde resin.
(d) Based On Molecular Forces:

(i)

Elastomers: Forces of interaction between polymer chains is weakest,

e.g. natural rubber, neoprene, vulcanized rubber.

(ii)

Fibers: Strong hydrogen bonds are present between the polymer chains.

They have high tensile strength e.g., nylon.polyster, silk, wool, orlon, rayon etc.

(iii)

Thermoplastics: They are linear/slightly branched chains molecules

capable of repeated softening on heating and hardening on cooling,e.g.,

polythene,PVC, polystrene, polypropene.

(iv)

Thermosetting Plastics: They are cross-linked or heavily

branched molecules, which on heating undergo extensive cross-linkages and become

infusible, e.g., bakelite,urea formaldehyde resin.
(e) Based On Growth Of Polymerization: Depending upon the

mechanism of Polymerization, polymers are classified as

(i)

Addition Polymers Or Chain Growth Polymers:

They follow mostly free radical mechanism.

(ii)

Condensation Polymers or Step Growth Polymers

because they are formed in gradual steps.

POLYMERS
POLYMER
Polythene
Teflon

(Poly
tetrfluoroethene
)
Poly acrylonitrile
Buna S
Buna N
Natural Rubber
Synthetic
Rubber(Neoprene)
Polypropene

MONOMER(Name & Structure)

USES
Addition or Chain Growth Polymer
Ethene CH2=CH2
Insulator, ,Packing material,
Lubricant, Insulator and making non-stick
cooking ware.
Tetrfluoroethene CF2=CF2

Acrylonitrile CH2=CH-CN
Buta-1,3-diene
+ Styrene
CH2=CH-CH=CH2
C6H5CH=CH2
Buta-1,3-diene
+
Acrylonitrile
CH2=CH-CH=CH2
CH2=CH-CN
2-Methylbuta-1,3-diene (Isoprene)
2-Chlorobuta-1,3-diene (Chloroprene)
Propene

CH3-CH=CH2

Polystyrene

Styrene

C6H5CH=CH2

Polyvinyl chloride
(PVC)

Vinyl Chloride CH2=CH-Cl

Terylene(Dacron)

Nylon 6
Bakelite

Phenol + Methanal

Melamine
PHBV (biodegradable)

Melamine + Methanal
3-Hydroxybutanoic acid +
3Hydroxypentanoic acid
Glycine
+ Amino caproic acid
H2N-CH2-COOH
H2N (CH2)5-COOH

Nylon 2 Nylon 6
(biodegradable)

Oil seals, Tank lining

Used for tyres after vulcanisation
Insulator, making conveyor belts and printing
rollers
Ropes, toys,pipes and fibres
Insulator, Wrapping material,toys, Radio and
television cabinets.
Rain coats, Hand bags, Vinyl flooring and water
pipe.

Condensation or Step Growth Polymers

Ethane-1,2-diol + Benzene-1,4-dicarboxylic Used for making fibres, safety belts, tents
acid
Hexamethylenediamine + Adipic acid
NH2(CH2)6NH2
HOOC(CH2)4COOH
Caprolactum

Nylon 66

For syntheticfibres and synthetic wool.

Automobile tyres and Foot wears

For making brushes,paratutes and ropes

Tyrescords,fabrics andropes
Combs,electricalswitches,handles of utensiles
and computer discs
Unbreakable crockery
Specialty packaging, orthopedic devices, In
controlled drug release

Urea-formaldehyde resin

Unbreakable cups , laminated sheet

Binding material
Glyptal
in preparation of mixed plastics and paints
******************************************************************************************
Semi-synthetic poly
Cellulose Acetate (Rayon)
Thermoplastic polymers
Linear or slightly branched / capable of repeatedly softening on heating and hardening on
cooling. Example : Polythene, Polystyrene, Polyvinyls, etc.
Thermosetting polymers
Cross linked or heavily branched molecules, / on heating undergo extensive cross linking in
moulds and again become infusible. These cannot be reused. Examples : Bakelite, Ureaformaldelyde resins.
Homo-polymer &
Homo-polymer Polymer of a single monomeric species. Example : Polythene , PVC
Co-polymer
Co-polymer Polymer of more than one monomer .Example : Nylon66, Bakelite
Initiators
Benzoyl Peroxide [ C6H5CO-O-O-CO-C6H5 ] (in freeradical addition polymerization)
Vulcanisation of Rubber.
Natural rubber is soft at high temp and brittle at low tempand absorbs water. To improve
these physical properties, it is heated with sulphur and an appropriate additive at a
temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the
reactive sites of double bonds and thus the rubber gets stiffened.

VSA

Urea + Formaldehyde
Ethane1,2-diol + Benzene-1,2-dicarboxylic
acid

(1 marks)

1.Name a natural elastomer.

Ans . Natural rubber.
2. Write name of a synthetic polymer which is an ester.
Ans. Nylon 6 or Nylon 6,6.
3. Name of monomer of Nylon 6.
Ans. Aminocaproic acid
4. Write the monomer units of Bakelite.
Ans. Phenol and formaldehyde.
5. Define a copolymer.
Ans.The polymers made by addition polymerisation from two different
monomers are termed as copolymers, e.g., BunaS, BunaN, etc.
6. Write one use of PVC.
Ans: In manufacture of rain coats& vinyl flooring.
7. Define Polymer.
Ans: Polymer is defined as very large molecules having
molecular mass (103107u). These are also referred
to as macromolecules,
8. Give an example of thermoplastics.
Ans: Thermoplastics are polythene, polystyrene, polyvinyls, etc.

9. To which class of polymers does Nylon66 belong?

Ans: Polyamides

10. Name the type of monomers interylene?

Ans: Ethylene glycol and terephthalic acid.
SA1

(2 marks)

1. Arrange the following polymers in increasing order of their intermolecular

forces.

(i) Nylon 6,6, BunaS, Polythene.

(ii) Nylon 6, Neoprene, Polyvinyl chloride.
Ans. (i) BunaS< Polythene<Nylon 6,6
(ii)Neoprene < Polyvinyl chloride< Nylon

2.Classify the following as addition and condensation polymers:

Terylene, Bakelite,
Polyvinyl chloride, Polythene.
Ans. (i) addition polymers :Polyvinyl chloride, Polythene.
(ii) condensation polymers: Terylene , Bakelite.
3.What is a biodegradable polymer ? Give an example of a biodegradable
aliphatic polyester.
Ans. Polymers which disintegrate by themselves over a period of time due to
environmental degradation by bacteria,etc.are called biodegradable
polymers. e.g. PHBV
4.How can you differentiate between addition and condensation polymerization
Ans. In addition polymerization the molecules of the same monomer or diferent
monomers add together on a large scale to form a polymer. The monomers used
are unsaturated compounds, e.g., alkenes, alkadienes and their derivatives.
Condensation polymerisation generally involves a repetitive condensation
reaction between two bifunctional monomers. These polycondensation
reactions may result in the loss of some simple molecules as water,
alcohol, etc., and lead to the formation of high molecular mass
condensation polymers. e.g. , Nylon 6,6.
5.What is meant by PTFE ?Give its popular name.
Ans.Polytetrafluoroethylene.it is called Teflon.
6.Write chemical name of (ZieglerNatta catalyst).
Ans: Triethylaluminium and titanium tetrachloride
7.Write down the two differences between thermoplastic and thermosetting
plastic and examples.
Ans:Thermoplastic 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, polyvinyls, etc.

Thermosetting plastic 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, ureaformaldelyde resins, etc.
8.DifferentiateNovolac and Bakelite on the basis of structure.
Ans: A linear product of Phenol - formaldehyde polymer is
Novolac, used
in paints.
Novolac on heating with formaldehyde undergoes cross linking to form an
infusible solid mass called bakelite. It is used for making combs, phonograph
records, electrical switches and handles of various utensils.
9. Distinguish between the terms homopolymer and copolymer and give an
example of each.
Ans: the addition polymers formed by the polymerisation of a single
monomeric species are known as homopolymers, e.g., polythene.
The polymers made by addition polymerisation from two different
monomers are termed as copolymers, e.g., BunaS, BunaN, etc. 10.
How will you differentiate between LDP and HDP?
Ans: 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
ofdioxygen or a peroxide initiator (catalyst).
Low density polythene is chemically inert and tough but flexible and a poor
conductor of electricity.e.g., squeeze bottles, toys and flexible pipes.
High density polythene: It is formed when addition polymerisation of
ethene takes place in a hydrocarbon solvent in the presence of a catalyst
ZieglerNatta catalyst at a temperature of 333 K to 343 K and under a
pressure of 67 atmospheres. HDP consists of linear molecules and has a
high density due to close packing. It is
more tougher and harder. It is used for manufacturing buckets, dustbins, bottles,
pipes, etc.

SAII

(3 marks)

1.Write the names of monomers of the following polymers:

(i) Nylon 6,6 (ii) Neoprene(iii) Buna N
Ans. (i) hexamethylenediamine and adipic acid.

(ii)

chloroprene.

(iii)1, 3 butadiene and acrylonitrile.

3.How are polymers classified on the basis of structure?
Ans.On the basis of structure, the polymers are classified as below:
(i) Linear polymers such as polythene, polyvinyl chloride,HDP etc.
(ii) Branched chain polymers such as low density polythene,LDP,etc. (iii)Cross
linked polymers such as bakelite, melamine, etc.
4. Write the monomers of the following polymers:
(i) BunaN (ii) Teflon(iii) Neoprene.
Ans.(i) 1, 3 butadiene and acrylonitrile (ii) tetrafluoroethene (iii) chloroprene.
6. Write use of each orion and Nylon6.
Ans: use of orion is clothing as a substitute for wool& for Nylon6.
Nylon6 is as fibrics

use of

8. Explain elastomeric polymers & Fibres

Ans: These are rubber like solids with elastic properties. In these
elastomeric polymers, 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 bunaS,
bunaN, neoprene, etc.
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.

9 . What is the function of sulphur in vulcanisation of rubber? Ans:

Sulphur introduces sulphur bridges.So it is become more tensile
strength,elasticity and resistance to abrasion etc.
10. Write Commercially Importants of following Polymers
(1)Polypropene (2)Polystyrene (3) Glyptal
Ans: (1) Manufacture of ropes, toys, pipes, fibres, etc.
(2)As insulator, wrapping material, manufacture of toys, radio and television
cabinets.
(3) Manufacture of paints and lacquers.
HOTS QUESTIONS
VSA (1mark)
1.What is the main constituent of bubble gum?
AnsStyrene butadiene copolymer (SBR).
2.What is a plasticizer?
Ans; The substances which are added to increase the softness of hard
polymers.
3.Draw the structures of the monomer of PAN.
Ans: CH2=CHCN
4.Give the name of polymer which is used for making non stick utensils.
Ans: Teflon(CF2=CF2)
5.What is the % of sulphur using during in vulcanization of rubber ?
Ans: 3% to 5%
SAI(2 marks)
1.Give the common and the IUPAC name of the monomer of natural rubber.
Ans: cisIsoprene & 2methyl1,3butadiene
2.Discuss the two main purpose of vulcanization of rubber.
Ans: (i)It makes the rubber hard.
(ii)It is more elastic.
(iii)It has more wear and tear resistance.
3.Explain the term Thermosetting polymers and give one example.
Ans: 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, ureaformaldelyde resins, etc.
4. Why should one always use purest monomer in free radical polymerisation?
Ans: Impurities of other substances if present,may inhibit or hinder the
chain propagation.
5.How is dacron obtained from ethylene glycol and terephthalic acid?
Ans: It is the condensation product of ethylene glycol and terephthalic acid
Carried out at 420 to 460K in the presence of catalyst mixture of zinc
acetate and antimony trioxide.
SAII(3 marks)
1.What does the following polymers stand for ?
(i)PVC (ii) DOP(iii) PAN
Ans: (1) Polyvinylchloride
(2)Dioctylphthalate
(3) Polyacrylonitrile
2. Why is Bakelite a thermosetting polymer?
Ans: It is a crosslinked polymer. On heating it sets permanently into a solid.Itcan
not be remoulded by heating again.
3.A regular copolymer of ethylene and vinyl chloride contains alternate
monomers of each type.What is the weight percent of ethylene in this
copolymer?
Ans: the weight percent of ethylene in this copolymer
[28/(28+62.5)]*100
30.93%
Acid
4.C6H10=NOH

polymerisation
B Give the products A& B.

A=Aminocaproic acid
B=nylon6
5.(i) Give an example of a synthetic rubber.

(ii) Mention main advantage of synthetic rubber.

(iii)Arrange the polymers in the increasing order of tensile strength,
Nylon6, BunaS,Polythene.
Ans: (i) synthetic rubber is BunaS
(ii) It is used for making oil seals, tank linings.
(iii) BunaS<Polythene< Nylon6

Polymers
Very Short Answer Type Questions (1 marks)
Q.1 Classify the following as addition and condensation polymers.
Terylene, Bakelite , polyvinyl chloride (PVC),polythene.
Sol. Addition polymers
Polyvinyl chloride and polythene
Condensation polymers
Treylene and Bakelite
Q2. Arrange the following in increasing order of their intermolecular forces.
(i)
Nylon-6,6, Buna-S , polythene
(ii)
Nylon-6 , neoprene , polyvinyl chloride
Sol.

Increasing order of the intermolecular forces of the polymers is as follows

(i)Buna-s < polythene <nylon-6,6
(ii)Neoprene < polyvinyl chloride < nylon-6

Q3. Is a

homopolymer or a copolymer?

Sol. It is a homopolymer because single type of monomer unit i.e., C6H5CH

CH2 undergo polymerisation.
Q4. Define the term polymerisation.

Sol. The process in which small molecules constitute the repeating units in a
polymer are called monomer units and are linked to each other by covalent
bond and this process of formation of polymers from respective monomers
is known as polymerisation.
Q5. In which classes, the polymers are classified on the basis of molecular
forces?
Sol.
i. Elastomers
ii. Fibres
iii. Thermoplastics
iv. Thermosetting polymers.
Q6. Write the name and structure of one of the common initiators used in
free radical addition polymerisation.
Sol. Benzoyl peroxide

Q7. Identify the monomer in the following polymeric structures

Sol. (i)Monomers are HOOC(CH2)8COOH and

Decanoic/Sebanic acid
H2N(CH2)6NH2
Hexamethylene diamine

(ii)Monomers

Q8. In nylon-6,6, what does the designation6,6 mean?

Sol. The amine and acid parts, of the monomers (adipic acid and
hexamethylene diamine which condense to give the polymer, each of them
contain 6 carbons.
Q9. Give an example of elastomers.
Sol. Buna-S, Buna-N, Rubber etc.
Q10. Identify the type of polymer.
--ABBAAABA
Sol. Copolymer.
Q11. Identify the type of polymer
AAAAA
Sol. Homopolymer.
Q12.Give the classification of polymers based on structures of polymers?
Sol. On the basis of structure of polymers are classified as
(i)Linear polymers
(ii)Branched chain polymers
(iii)Cross-linked or Network polymer.
Q13. Which factor impacts crystalline nature to polymer like nylon?
Sol. Strong intermolecular forces like hydrogen bonding, lead to close packing of
chains that impacts crystalline character.

Q14.Which of the following are addition polymers :

;Neoprene?
Sol. Neoprene and Teflon are addition polymers.

Terylene ;Teflon

Q15. Can enzyme be called a polymer?

Sol. Yes, they are biocatalysts which are proteins and therefore they are
polymers.

Q16. Explain the difference between Buna-N and Buna-S.

Sol. Buna-N is a copolymer of 1,3-butadiene and acrylonitrile whereas Buna-S is
a copolymer of 1,3butadiene and styrene.

Q17. What are the monomeric repeating units of nylon-6 and nylon-6,6?

Sol. Nylon-6

Q18. Write the monomers used for getting the following polymers
(i)Polyvinyl chloride
(ii)Teflon
(iii)Bakelite.

Sol.

Q19. A natural linear polymer of 2-methyl-1, 3 butadiene becomes hard on

treatment with sulphur between 373 to 414K and SS bonds are
formed between chains.
Write the structure of the product of this treatment?

Sol.

Q20. Which type of biomolecules have same structural similarity with

synthetic polyamides? What is the similarity?
Sol. Protiens have structural similarity with polyamides because both have amide
linkage.
Q21. What is the repeating unit in the condensation polymer obtained by
combining HO2CCH2CH2CO2H(succinic acid) aand H2NCH2CH2NH2(ethylene
diamine)?
Sol. [-NHCH2CH2NHCOCH2CH2CO---]n--.
Q22. Draw the molecular structure of the monomers of
(1)PVC
(2) Teflon
Sol. (i) CH2=CHCl
Vinyl chloride
(ii)CF2=CF2
Tetrafluroethene.
Q23. Write the structures of monomers used in preparations of (i)Teflon
(ii)PMMA.
Sol. (i)CF2=CF2 tetrafluriethene

COOCH3
|
(ii)Methyl methacrylate, CH2=CCH3.
Q24. Give one example of a condensation polymer.
Sol. Nylon-6,6 is an example of condensation polymer because it is the result of
condensation reaction between adipic acid and hexamethlyendiamine.
Q25. Define plasticizers.
Sol. These organic compounds which added to plastics make them soft and
workable are known as plasticizers e.g., tricresyl phosphate , di-n-octylphthalate.

Q26. Name the main constituent of bubble gum?

Sol. Styrene-butadiene copolymer.
Q27.Write the monomers of the cellulose and polythene?
Sol. Cellulose -D-glucose
Polythene --- Ethane.

Q28. Give an example of a polymer which is used to make cups for hotdrinks?
Sol. Urea-formaldehyde resin.

Q29. Name the monomers of

(i)Nylon 2-nylon-6 polymer
(ii)Teflon.
Sol. (i)Nylon 2-nylon-6 polymer is a polymer of
H2NCH2COOH and H2N(CH2)5COOH.
Glycine
Amino caproic acid.
Q30. Name a synthetic polymer that contains amide.
Sol. Nylon-6,6.

Short Answer Type Questions {2 Marks Questions}

Que.1:- (1) How does vulcanisation change the character of natural rubber?
(2) Why are the number, 6,6and6 put in the names of nylon-6,6 and nylon6?
Sol.:- (1) Valcanisation of natural rubber makes it hard and even more elastic. It
possess more wear and tear properties. It is used in automobile tyres.
(2) Nylon-6,6 and nylon-6 are the polymer of adipic acid, hexamitheylenediamini
and caprolactam respectively. Each of them has 6 carbon atom. Therefore
number 6,6 and 6 put in the names refer to the number of carbon atoms in the
monomers involved.
Que.2:- Explain the term coplymerisation and give two examples.
Sol.:- Coplymerisation is the process in which two or more diffrent monomers
polmerise together to form copolymer. e.g., Buna-S and Bina-N

Que.3:- What are the natural and synthetic polymers ? Give two example of
each type.
Sol.:- (1) Natural Polymers. These are found in plants and animals. e.g.,
cellulose, starch(polymer of glucose),
Protein .
(2) Synthetic Polymers These are man-made polymers that are used in day to
day life and in industries. e.g., Synthetic fibers, synthetic rubber
Que.4:- What are polymers?
Sol.:- The word 'ploymer' is coined from two Greek words 'poly' means 'many'
and 'mer' means 'unit/part'.
Ploymers can be defined as compound of high molecules formed by combination
of large numbe of small molecules. The small molecules which constitute the
reparing unit in polymer are called monomer unit and are linked to each other
by covalebt bond and this process of formation of polymers from respective
monomers is known as polymerisation.
e.g.-

Que.5:- How is the following resin intermediate prepared and which

polymer is formed by this monomer unit?

Sol.:Melamine and formaldehyde are the staring material for this intermediate. Its
polymerisation leads to the formation of melamine polymers.

Que.6:- (1) What is the role of benzoyl peroxide in polymerisation of

ethene?
(2) What are LDP and HDP ? How are they prepared?
Sol.:- (1) Bezoyl peroxide acts as a initiator in the chain reaction. It dessociate to
give radicals.

(2) LDP Low Density Polyethene.

Prepation By Polymerisation of ethene at 350-570 C Teampratur and 10002000 atm high pressure, in the branched presence of peroxide initator: it is a
branched chain polymer.
HDP High Density Polyethene
Preparation Polymerisation of ethene at temprature of 333k to 343k And 6-7
atm prssure in the presence of Ziegler- Natt cataylst. HDp is a linear polymer.
Que.7:- Identify the monomer in the following polymeric sttructures.

Sol.:- (1) (a) Decanedioic acid

HOOC (CH2)8 COOH
(b) Hexamethylenediamine
H2N- (CH2) - NH2
(2) (a) 2,4,6- triamino- 1,3,5- triazine or melamine
(b) Formaldehyde or methanal (HCHO)

Short Answer Type Questions (3 marks)

Q1- Explain the terms polymer and monomer.

Ans- Polymers can be defined as compounds of high molecular mass (103-107 u)

formed by combination of large number of small molecules. The small molecules
which constitute the repeating units in a polymer are called monomer units and
are linked to each other by covalent bond and this process of formation of
polymers from respective monomers is known as polymerization. As polymers
are single, giant molecules these are also called macromolecules.
Q2- Write the names and structures of the monomers of the following
polymers
(i)
Polystyrene
(ii) Teflon
Ans- (i) Polystyrene
Monomer Styrene (Vinyl benzene)
Structure
CH==CH2

Styrene
(ii)

Teflon
Monomer Tetrafluoroethene
Structure
F

F
C == C

F
F
Q3- How are polymers classified on the basis of structure?
Ans- (i) Linear Polymers- These consist of long and straight chains. They have
high densities, high melting points and high tensile strength. Thus, these are well
packed structures e.g., high density polythene, polyvinyl chloride etc. These are
represented as
(iii) Branched Chain Polymers- These contain linear chains having some
branches. Due to their irregularly packed structure they have low tensile
strength, low densities and lower melting point as compared to linear
polymer e.g. low density polythene, glycogen etc. These are depicted as

Diag. BRANCHED CHAIN POLYMERS

(iii) Cross-Linked or Network Polymers- These are usually formed from bifunctional and tri-functional monomers and contain strong covalent bonds
between various linear polymer chains. These are hard and rigid e.g. bakelite,
melamine etc. These are depicted as

Diag. CROSS-LINKED POLYMERS

Q4-Distingush between the terms homopolymer and copolymer and give
an example of each?
Ans- Homopolymers are those polymers whose repeating structural units are
derived from only one type of monomer unit e.g. polythene, PVC, PAN, nylon-6,
Teflon etc. Whereas copolymers are those polymers whose repeating structural
units are derived from different types of monomer molecules e.g. Buna-S, nylon6,6, melmac, polyester etc.
Q5- How do you explain the functionality of a monomer?
Ans- By functionality, we mean the number of bonding sites in a molecule. For
instance, the functionality of ethane, propene, acrylonitrile is one because such
molecules can react at one site while that of adipic acid, 1, 3-butadiene,
hexamethylenediamine is two because they can bond at two positions with other
molecules.
Q6- Draw the schematic representative of linear, branched chain and crosslinked polymers.
Ans- DIAG.
DIAG.
DIAG.
Q7- Write the names and structures of the monomers of the following
polymers
(i) Buna-S
(ii) Buna-N
(iii) Dacron
(iv) Neoprene
Ans- (i) Buna-S
CH2 == CHCH == CH2;
1, 3-butadiene
(ii) Buna-N
CH2==CH2CH==CH2;

C6H5CH==CH2
Styrene

CH2==CHCN

1, 3- butadiene
(iii) Dacron

Acrylonitrile

HOCH2CH2OH;
HOOC(C6H4)COOH
Ethyl glycol
Terephthalic acid
(iv) Neoprene
Cl
CH2==CCH==CH2
Chloroprene
Q8- How does the presence of double bonds in rubber molecules influence
their structure and reactivity?
Ans- Natural rubber is cis-polyisoprene and it is obtained by 1, 4-polymerisation
of isoprene units.
H3C
H
H 3C
H
C==C
CH2
CH2
C==C
~~~ H2C
CH2
C==C
CH2
CH2--~~~
H3C
H
Natural
rubber
The cis-configuration at double bonds does not allow the polymer chains to come
closer for effective interactions and hence intermolecular forces are quite weak.
As a result, natural rubber, cis-polyisoprene has a randomly coiled structure and
hence shows elasticity.
Q9- Differentiate thermoplastics and thermosetting polymers with two
examples of each.
AnsS.No. Thermoplastic Polymer
1
These are linear or slightly
branched long chain molecules.
2
These are capable of repeatedly
softening on heating and
hardening on cooling.
3
Intermolecular forces are
intermediate of elastomer and
fibres.
4
These can be reused e.g.
polythene, polyvinyl chloride
(PVC)

Thermosetting Polymer
These are cross-linked or heavily
branched molecules
On heating, these undergo
extensive cross-linking and
become infusible.
Intermolecular forces are
strongest.
These cannot be reused e.g.
bakelite, urea- formaldehyde
resin.

Q10- Write the free radical mechanism for the polymerization of ethane?
Ans- Alkenes/dienes and their derivatives are polymerized in the presence of a
free radical generating initiator (catalyst) like acetyl peroxide, benzoyl peroxide,
etc e.g. polymerization of ethene to polythene.
It consist of heating or exposing to light a mixture of ethene with a small amount
of benzoyl peroxide (as an initiator).
This process is completed in three steps given below
Step I- Chain Initiating Step
Firstly, the phenyl radical is formed by benzoyl peroxide. Then phenyl radical
added to the double bond of ethene molecule (monomer) to form a new and a
large free radical through homolysis.
O
C6H5COOCC6H5
Benzoyl peroxide
O
2C6H5C--O
2C6H5
Phenyl radical
C6H5 + CH2 == CH2
C6H5CH2CH2
Ethene (Monomer)
Big free radical
Step II- Chain Propagation Step
The new big free radical thus formed in the chain initiating step reacts with
another molecule of etheneto form another bigger sized radical. Thus, the
repetition of this sequence with new and bigger radicals tends to carry the
reaction forward.
C6H5 -- CH2 -- CH2 + CH2 == CH2
C6H5 -- CH2 -- CH2 -- CH2 -- CH2
C6H5 (CH2 -- CH2)n-- CH2 -- CH2
Step III- Chain Termination Step
Ultimately, the growing free radical chain may get terminated by reactions which
consume these free radicals by combination of free radicals in different ways to
form polythene.
C6H5 (CH2 -- CH2)n-- CH2 -- CH2 +
C6H5(CH2-- CH2)n-- CH2-- CH2
C6H5(CH2-- CH2)n -- CH2 CH2
CH2(CH2 -- CH2)n -- C6H5
Polythene

Q11- How can you differentiate between addition and condensation

polymerization?
Ans- In addition polymerization, the molecules of the same or different
monomers add together to form a large polymer molecule without the elimination
of simple molecules like H2O, HCl etc. Condensation polymerisation is a process
in which two or more bifuntional molecules undergo a series of condensation
reactions with the elimination of some simple molecules like H2O, HCl, alcohol
and leading to the formation of polymers.
Q12-Write names of monomers of the following polymers and classify them
as addition and condensation polymers.
(i) Teflon
(ii) Bakelite
(iii) Natural rubber
Ans- (i) Tetrafluoroethene (CF2 == CF2 ) is the monomer of teflon. It is an
addition polymer.
(ii) Formaldehyde and phenol are the monomers of the bakelite. It is a
condensation polymer.
(iii) Isoprene is the monomer of the natural rubber. It is an addition polymer.
Q13- Discuss the main purpose of vulcanization of rubber?
Ans-Vulcanisation is the heating of natural rubber with sulphur and an
appropriate additive at a temperature range between 373 K to 415 K. Sulphur
forms cross-links at the reactive sites of the double bond and thus rubber gets
stiffened i.e. becomes less sticky and plastic, more resistant to swelling by
organic liquids and has enhanced elasticity. Physical properties of rub VBer can
be impured by vulcanization.
Q14- How is Dacron obtained from ethylene glycol and terephthalic acid?
Ans- The following is the equation for the formation of Dacron.
nHOCH2CH2OH + nHOOC

CHOOH

420 460 K

Terephthalic acid
O
--OCH2CH2OC

O
C

+ (2n 1) H2O

Q15-What is biodegradable polymer? Give an example of a biodegradable

aliphatic polymers?
Ans- Biodegradable polymers are those polymers which get decomposed by
themselves over a period of time due to environmental degradation by bacteria.
e.g. PHBV (Poly B-hydroxy butyrate-co-B-hydroxy valerate).
nHO CH CH2 COOH + nHO CH CH2 -- COOH
CH3
3-hydroxybutanoic acid

Polymerisation

CH2CH3
3-hydroxypentanoic acid
--OCHCH2COCHCH2C
CH3

CH2CH3

Q16- Give one example of each

(i) Addition polymers
(ii) Condensation polymers
(iii) Copolymers
Ans- (i) Addition polymers (--CH2CH2--)n

polyethylene

(ii) Condensation polymers

O

--OCH2CH2OC

C
n

Dacron
(iii) Copolymers
--CH2CH==CHCH2CHCH2--

Buna-S