CHAPTER

POLYMERS

Syllabus

Copolymerization, some important polymers: natural and synthetic like polythene, nylon, polyesters, bakelite, rubber. Biodegradable and non-biodegradable polymers.

Chapter Analysis

2016 2017 2018

List of Topics D D OD OD D/OD

Polymerization of ethene 1Q (3 marks)* Identification/Structure 1Q 40 1Q 1Q

of monomers in polymers (3 marks)* (3 marks) (3 marks)# (3 marks)

Properties of Polymers 1Q 10. (3 marks)* (3 marks)# Vulcanization of Rubber

(3 marks)#

• One question of 3 marks was asked. First choice have questions on Polymerization of Ethene, Identification of Monomers in polymer and arrangement of polymers in their increasing Intermolecular Forces.
• #One question of 3 marks on Vulcanization of Rubber, Identification of Monomers in polymer and arrangement of polymers in their increasing Intermolecular Forces was asked.

On the basis of above analysis, it can be said that from exam point of view, Identification/Structure of monomers in polymers and Properties of Polymers are the most important topics of the chapter.

Revision Notes

> Polymers: Polymers are defined as the high molecular mass macromolecules, which consists of repeating structural units derived from the corresponding monomers.

➣ Polymerisation: The process by which monomers are converted into polymers is called polymerisation.

<math>nCH_2 = CH_2 \xrightarrow{350 - 570 \text{ K}, 100 - 200 \text{ atm}} (-CH_2 - CH_2 - CH_2)_n</math>

Ethene Polythene

(Monomer) (Polymer)

➣ Natural Polymers : They are found in nature, mostly in plants and animals e.g., proteins, natural rubber etc.

➣ Synthetic Polymers: These are man-made polymers prepared in the laboratory. e.g., polythene, teflon, nylon etc.

➣ Copolymerisation is a polymerisation reaction in which a mixture of more than one monomeric species is allowed to polymerise.

Copolymers: The polymers made by addition polymerisation from two different monomers.

332 Oswaal CBSE Chapterwise & Topicwise Question Bank, CHEMISTRY, Class – XII

<math display="block">nCH_2 = CH - CH = CH_2 + nC_0H_5CH = CH_2 - Polymerisation \rightarrow \begin{bmatrix} CH_2 - CH = CH - CH_2 - CH - CH_2 \end{bmatrix}</math>

1, 3-Butadiene Styrene

Butadiene - styrene copolymer

[Buna-S]

➣ Condensation Polymers: These polymers are formed by the repeated condensation reactions between different bifunctional or trifunctional monomer units usually with elimination of small molecules such as water, alcohol, hydrogen chloride etc. e.g., nylon 6, 6 and nylon, terylene etc.

<math>nH_2N(CH_2)_6NH_2 + nHOOC(CH_2)_4COOH \longrightarrow \{-NH(CH_2)_6NHCO(CH_2)_4CO-\}_n + 2nH_2O</math> Hexamethylene diamine Adipic acid Nylon 6, 6

➣ Condensation Polymers:

1. Polyesters: These are polymers having large number of ester linkages. e.g.,

1. Terylene: It is resistant to action of chemical and solvent. It has a low moisture absorbing power. It is also called dacron. It is used in dress materials like sarees. It is used as a blend with cotton and wool to give terrycot and terrywool.

<math>nHOCH_2 - CH_2 - OH + nHO - C - OH - OH - OH - OH - OH - OH - O</math> Ethylene glycol Terephthalic acid Terylene (Dacron)

1. Glyptal or alkyl resin: These are three dimensional cross-linked polymers. It is tough and flexible. It

is used in adherent paints, lacquers and building materials like asbestos and cement.

<math>\circ</math> O nHO — CH₂ — CH₂ — OH + nHO — ∕n

Ethylene glycol

Phthalic acid Glyptal

1. Polyamides: Those polymers which have large number of amide linkages are called polyamides, e.g.,

1. Nylon-6, 6: It can be cast into sheets or fibres. Nylon fibres have high tensile strength. They are tough and resistant to abrasion. They are also elastic in nature. It is used to make bristles of toothbrush, climbing ropes, fishing nets and parachute fabrics. It is a condensation polymer of adipic acid and hexamethylene diamine.

<math display="block"> \begin{array}{cccccccccccccccccccccccccccccccccccc</math> diamine Nylon-6, 6

1. Nylon-6: It can be cast into sheets and fabrics. It is tough and strong.

Η NOH Beckmann <math>H_2C</math> <math>C=O</math>

Oxidation NH₂OH Rearrangement

<math>O_2</math> <math>H_2SO_4</math> <math>H_2C</math> <math>CH_2</math>

Cyclohexane Cyclohexanone Cyclohexanoxime <math>CH_{2}</math>

Caprolactam