3.12 Polymers

Question 1

What does condensation polymerisation involve?

Answer 1

The reaction of 2 monomers (containing 2 different functional groups) with the loss of a small molecule (H2O or HCl)

Question 2

Which 2 monomers form polyesters?

Answer 2

Dicarboxylic acid/diacyl chloride + diol

Question 3

What are polyesters used for?

Answer 3

Fibres for clothes

Question 4

Which 2 monomers form polyamides?

Answer 4

Dicarboxylic acid/diacyl chloride + diamine

Question 5

What is nylon used for?

Answer 5

Fibres for clothing
Parachutes, tents, ropes

Question 6

What is kevlar used for?

Answer 6

Bulletproof vest
Fireproof/fire resistant

Question 7

Describe the structure and bonding of Kevlar:

Answer 7

• Kevlar chains are planar so can pack closely together
• So intermolecular forces between neighbouring molecules are stronger than in other molecules
• Kevlar also has H-bonds»_space; very strong

Question 8

Where does the H-bond occur in Kevlar?

Answer 8

Between the C=O of one amide link and the N-H of another

Question 9

How reactive are addition polymers and why?

Answer 9

Chemically inert - because the C-C bonds between the repeat units are strong and non-polar (not susceptible to attack by nucleophiles e.g. water)

Question 10

Which catalysts can be used to hydrolyse polyesters and polyamides?

Answer 10

HCl or NaOH (strong aqueous acid/strong aqueous base)

Question 11

Conditions for hydrolysis of polyamides and polyesters:

Answer 11

• HCl/NaOH catalyst (e.g. 6 moldm-3)
• heat and reflux

Question 12

Products of acid hydrolysis of polyesters:

Answer 12

Dicarboxylic acid + diol

Question 13

Products of alkali hydrolysis of polyesters:

Answer 13

Diol + carboxylate salt
(Dicarboxylic acid reacts with the NaOH)

Question 14

Products of acid hydrolysis of polyamides:

Answer 14

Dicarboxylic acid + diammonium ion (NH3+ groups at either end)

Question 15

Products of alkali hydrolysis of polyamides:

Answer 15

Carboxylate salt + diamine

Question 16

Why can condensation polymers be hydrolysed?

Answer 16

The bonds between the repeating units are polar so are susceptible to attack by nucleophiles e.g. water

Question 17

What are the advantages of burying waste polymers?

Answer 17

• relatively cheap
• easy

Question 18

What are the disadvantages of burying waste polymers?

Answer 18

• requires areas of land
• as the waste decomposes it releases methane and toxins which could wash into water supplies