IIT JEE13-Chemistry-Hand Out-Chem polymer.pdf

Hand-Out Chemistry Polymer

POLYMER 1.

Polymers are high molecular mass substance consisting of large number of repeating structural units. As polymers are single, giant molecules i.e. big size molecules, they are also called macromolecules

2.

Simple molecules which combine to form polymers are called monomers

3.

Process of formation of polymers from respective monomers is called polymerization

Classification Based On 1.

Source of availability (i)

Natural Polymers: Polymers obtained from nature, mostly plants and animals. Examples: Cellulose, Starch etc.

(ii)

Synthetic Polymers: Polymers prepared in laboratory. Examples: Teflon, Nylon 6, 6, Syntehtic rubber (Buna-S) etc.

(iii) Semi Synthetic Polymer: Polymers derived from naturally occurring polymers by carrying out chemical modifications. Examples: Rayon (Cellulose acetate), Cellulose nitrate, etc. 2.

Structure of Polymter (i)

Linear Polymers: Polymer consist of long and straight chains. Example: High density polythene, polyvinyl chloride, etc.

(ii)

Branched Chain Polymers: Polymers contains linear chains having some branches. Examples: Low density polythene.

(iii) Cross linked or network polymers: Polymers in which monomer units are cross linked together to form a 3 dimensional network polymers. Examples: Bakelite, Melamine, etc. 3.

Mode of Polymerisation: (i)

Addition Polymers: Polymers are formed by the repeated addition of monomers with double and triple bonds. (a)

Homopolymers: Polymers formed by the polymerisation of a single monomeric species. Examples: Polythene, Polystyrene.

(b)

Copolymers: Polymers formed by addition polymerisation of two different monomers. Examples: Buna-S, Buna-N.

(ii)

Condensation Polymers: Polymers formed by repeated condensation reaction between two different bifunctional or tri-functional monomeric units with elimination of simple molecules. Examples: Nylon 6, 6, Nylon 6.

4.

Molecular Forces: (i)

Elastomers: Polymer chain are held together by weakest intermolecular forces. Polymers are rubber-like solids with elastic properties. Examples: Buna-S, Buna-N, Neoprene.

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Hand-Out Chemistry Polymer (ii)

Fibre: Polymers have strong intermolecular force like hydrogen bonding. Fibres are the thread forming solids which possess high tensile strength and high modulus. Examples: Nylon 6, 6, Polyesters

(iii) Thermoplastic polymers: Polymers are held by intermolecular forces which are in between those of elastomers and fibres. These polymers are capable of repeated softening on heating and hardening on cooling. Examples: Polythene, Polystyrene. (iv) Thermosetting Polymers: Polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and eventually undergoes a permanent. Examples: Bakelite, Urea-formaldelyde resins. 1.

LDP Monomer:

Ethene - Under HT HP in presence of peroxide initiator as a catalyst.

User/Properties: Chemicaaly inert, tough but flexible poor conductors electricity, used in square bottles, toys insulation of wires, flexible pipes. Specified under: Polythene, addition polymers, thermoplastic, polymers, branched polymers homopolymers. 2.

HDP Monomer:

Ethene - In presnece of hydrocarbon solvent + Ziegler - Natta catalyst (triethylaluminium and titanium tetrachloride) 333 K - 343 K, 6 - 7 Bar

User/Properties: High density due to close packing chemcially inert more tough and hard. Manufacturing of buckets, dustbings, bottles, pipes etc. Specified under: Addition polymenisation thermoplastic polymers linear polymers, homoporymar. 3.

Polytetrafluroethene (Teflon) Monomer:

n CF2 = CF2 (HP, catalyst) Tetrafluoroethene

Polymer:

[ CF2  CF2 ] Teflon

User/Properties: Chemically inert, making oil seals, gaskets, non-stick surface coated utensils. Specified under: Addition polymers 4.

Polyacrylonitrile Monomer:

n CH2 = CHCN (Peroxide catalyst)

CN Polymer:

[ CH2 – CH ]n Polyacrylonitrile

User/Properties: Used as substitutes for wool in making commercial fibres as orlon acrilan. Specified under: Addition polymerisation.

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Hand-Out Chemistry Polymer 5.

Nylon 6, 6 Monomer:

n HOOC(CH2)4COOH + n H2N(CH2)6NH2 Hexamethylenediamine with adipic acid.

H Polymer:

H

O

O

[ N – (CH2)6 – N – C(CH2)4 – C ]n Nylon 6, 6

User/Properties: Making sheets, bristles for brushes and in textile industry. Specified under: Condensation polymerization fibres, synthetic polymers, polyamides. 6.

Nylon 6 Monomer:

Caprolactum with water at a high temperature H

N H 2C

C=O

H2 C

CH2

H 2C O Polymer:

CH2 H

[ C – (CH 2)5 – N ] n

User/Properties: Manufacture of tyre cords, fabrics and ropes Specified under: Condensation polymerization, fibres, synthetic polyers, polyamides 7.

Dacron Monomer:

Ethylene glycol and terephthalic acid in presence of zinc acetate n HOH2C – CH2OH + n HOOC – C6H5 – COOH

Polymer:

Dacron (terylene)

O [ OCH2 – CH2 – C

O C ]n

User/Properties: Crease reistant, used in blending with cotton and wool fibres, used in safety helmets, etc. Specified under: Condensation polymerization, polyesters fibres. 8.

Bakelite Monomer:

Novolac on heating with formaldehyde

OH CH2

Polymer:

Bakelite

User/Properties: For making combs, electrical switches, computer disces. Specified under: Condensation polymerisation, synthetic polymers, thermosething, polymer, crosslin Chemistry/Class XII

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Hand-Out Chemistry Polymer 9.

Melamine formaldehyde polymer Monomer:

Melamine and formaldehyde (HCHO)

N

H 2N

NH2

N

N NH2

Polymer:

Melamine polymer N

[ HN N

NH – CH2 ]n N

NH

User/Properties: For manufacture of unbreakable crockery. Specified under: Condensation polymerisation of melamine and formaldehyde. 10.

Buna-S Monomer:

1,3-butadiene and styrene nCH2 = CH – CH = CH2

CH – CH2

Polymer:

[– CH2 = CH – CH = CH2CH(C6H5)CH2 –]

User/Properties: Manufacture of autotyres, floortiles, footwear components, resistant to the action of petrol, oil used in making oil seals, tank lining, etc. Specified under: Copolymerization synthetic polymers Elasomer, copolymerization 11.

Natrual rubber Monomer:

Isoprene or (cis-1,4-polyisoprene) CH3 H2C = C – CH = CH2

Polymer:

Natural rubber

User/Properties: Weak van der Waals interactions and has a coiled structure Specified under: Copolymerisation linear polymer elastomers, rubber 12.

Neoprene / olychloroprene Monomer: Polymer:

Chloroprene Cl

[ CH2 – C = CH – CH2 ]n Neoprene

User/Properties: Manufacturing coveyor belts, gaskets and hoses Specified under: Synthetic Rubber, Chloroprene, Eastover

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Hand-Out Chemistry Polymer 13.

Buna-N Monomer:

1,3-butadiene (n CH2 = CH – CH = CH2), acrylonitrile (CH2 = CHCN)

CN Polymer:

[ CH2 – CH = CH – CH2 – CH2 – CH ]n Buna - N

User/Properties: resistant to the action of petrol, lubricating oil and organic solvents. It is used in making oil seals, tank lining, etc. Specified under: Copolymerization, biodegertable polymers. 14.

Poly- hydroxybutyrate-co--hydroxy valerate (PHBV) Monomer:

3-hydroxybutanoic acid and 3-hydroxypentanoic acid.

O – CH – CH2 – C – O – CH – CH2 – C Polymer:

CH3

O

CH2CH3

O n

PHBV

User/Properties: speciality packaging, orthopaedic devices and in controlled release of drugs. Specified under: Biodegradable 15.

Nylong 2-nylon 6 Monomer:

Glycine (H2N – CH2 – COOH), amino caproic acid [H2N(CH2)5COOH]

Specified under: Homopolymers, topes toys fibres 16.

Polypropene Monomer:

Propene

CH3 Polymer:

CH2 – CH

n

User/Properties: As insulator, wrapping material, manufacture of toys, radio and television cabinets. 17.

Polystyrene Monomer: Polymer:

Styrene

C6 H 5

CH2 – CH

n

User/Properties: Rain, coats, hand bags, water pipes Specified under: Linear polymers 18.

PVC Monomer:

Vinyl chloride Cl

Polymer:

CH2 – CH

n

User/Properties: Manufacture of paints and lacquers Chemistry/Class XII

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Hand-Out Chemistry Polymer 19.

Glyptal Ethylene glycol, phthalic acid

Monomer:

OCH2 – CH2OOC Polymer:

CO n

Addition Polymerisation or Chain Growth Polymerisation: Most common mechanism for addition polymerisation reactions is free radical mechanism Step 1: Chain initiating step:

O

O

C6 H 5 – C – O – O – C – C 6 H 5

O 2C6H 5 – C – O

Benzoyl peroxide

2C6H 5 + 2CO2 Phenyl radical

C6H5 + CH2 = CH2 C6H5 + CH2 – CH2 Step 2: Chain propagating step: C6H5 – CH2 – CH2 + CH2 = CH2

C6H5 – CH2 – CH2 – CH2 – CH2

C6H5 –( CH2 – CH2 –)n CH2 – CH2 Step 3: Chain terminating step:

C6H5 –( CH2 – CH2 –)n CH2 – CH2 +

C6H 5 –( CH 2 – CH 2 –)n CH2 – CH 2– CH2 – CH2 –( CH 2 – CH 2 –)n C 6H 5

C6H5 –( CH2 – CH2 –)n CH2 – CH2

Polythene

Vulcanisation of rubber Heating a mixture of raw rubber 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. Q1.

Write an equation for the Chemistry involved when a drop of hydrochloric acid make a hole in nylon stockings.

Ans.

The (— CO — NH —) amide bond in nylon gets hydrolysed.

Q2.

Fibres are of crystalline structure. Why ?

Ans.

Fibres have strong intermolecular forces of attraction which leads to close packing of their chains and impart crystalline structure.

Q3.

Which artificial polymer is present in bubble gum or chewing gum ?

Ans.

Bubble gum or chewing gum contains synthetic Styrene-butadiene rubber.

Q4.

Name the polymer used for making medicinal Capsule.

Ans. Q5.

PHBVUC Polyhydroxy butyrate-CO--hydroxy valerated.Ans. Which colligative property is used to determine the molecular masses of the polymers ?

Ans.

Osmotic pressure is the colligative property used to determine the molecular masses of polymer.

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Hand-Out Chemistry Polymer Q6.

How do double bonds in the rubber molecule influence their structure and reactivity?

Ans. Q7.

Due to presence of double bond the rubber molecule show cis-configuration because which the Why are the No. of 6, 6 and 6 put in the names of nylon-6, 6 and nylon-6 ?

Ans.

both the monomers of nylon-6, 6 namely hexamethylene diamine and adipic acid contain six carbon atom each. The no. of 6 in nylon-6 contains six carbon atom each. The no. of 6 in nylon-6 indicates that its monomer Caprolectum has six carbon atom in its molecule.

Q8.

Could a copolymer be formed in both addition and condensation polymerisation or not ? Explain.

Ans.

Yes, though copolymers are mostly addition polymers like styrcue butadiene rubber and butyl rubber, the term can be used for condensation polymers also eg. for example. (i)

Addition polymerisation of styrene and butadiene form copolymer styrene butadiene rubber. n CH2 = CH — CH = CH2 + n C6H5CH = CH2 ———® C 6 H5 |

(ii)

(— CH2 — CH = CH — CH2)n — CH2 — CH —)n Condensation polymer became thylene diamine and adipic acid form nylon-6, 6. n HOOC — (CH2)4 — COOH + n H2N — (CH6) — NH2 ———® adipic acid hexamethylene — n H2O diamien

Q9.

Ans.

(— NH (CH2)6 — NH — CO — (CH2)4 — CO —)n Arrange the following polymer in increasing order of their molecular forces : (a)

nylon-6, 6, Buna-S, polythene.

(b)

nylon-6, Neoprene, polyvinyl chloride.

(a)

Buna S < Polythene < Nylon-6, 6.

(b)

Neoprene < Polyvinyl Chloride < Nylon-6.

Q10. Explain the difference between Buna— S and Buna — N. Ans.

Buna — N is a copolymer of 1, 3-butadiene and acrylo nitrile, Buna — S is a copolymer of 1, 3-butadiene and styrene.

Q11.

Why should we always use purest monomer in free radical mechanism ?

Ans.

Monomer has to be as pure as possible because the presence of any other molecule during free radical polymerisation can act chain initiator or inhibitor which will interfere with the normal polymerisation reaction.

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