Topic 35: Polymerisation

Question 1

Definitions I:
(a) Condensation polymerisation
(b) Polyester
(c) Polyamide

Answer 1

Definitions I:
(a) Monomers join, releasing small molecules, e.g., H₂O.
(b) Polymer with ester links, e.g., from diol + diacid.
(c) Polymer with amide links, e.g., from diamine + diacid.

Question 2

Write equations for:
(a) HOCH₂CH₂OH + HOOCCH₂COOH → polyester [1 Mark]
(b) H₂NCH₂CH₂NH₂ + ClOCCH₂COCl → polyamide [1 Mark]

Answer 2

(a) n HOCH₂CH₂OH + n HOOCCH₂COOH → [-OCH₂CH₂OCOCH₂CO-]ₙ + 2n H₂O (1 mark)
(b) n H₂NCH₂CH₂NH₂ + n ClOCCH₂COCl → [-NHCH₂CH₂NHCOCH₂CO-]ₙ + 2n HCl (1 mark)

Question 3

Deduce the repeat unit for HOCH₂CH₂OH + HOOCCH₂CH₂COOH polyester. [2 Marks]

Answer 3

-OCH₂CH₂OCOCH₂CH₂CO- (1 mark)
From ester link between diol and diacid (1 mark)

Question 4

In a lab, identify the monomers in [-NHCH₂CH₂NHCOCH₂CO-]ₙ polyamide. [2 Marks]

Answer 4

H₂NCH₂CH₂NH₂ and HOOCCH₂COOH (1 mark)
Diamine and diacid form amide links (1 mark)

Question 5

Why are poly(alkenes) like poly(ethene) hard to biodegrade? [2 Marks]

Answer 5

Stable C-C bonds, chemically inert (1 mark)
No sites for microbial attack (1 mark)

Question 5

Predict the polymerisation type for:
(a) CH₂=CH₂ [1 Mark]
(b) H₂NCH₂COOH [1 Mark]

Answer 5

(a) Addition, C=C opens (1 mark)
(b) Condensation, -NH₂ and -COOH react (1 mark)

Question 6

Describe the formation of a polyester from HOCH₂CH₂COOH and its repeat unit. [3 Marks]

Answer 6

n HOCH₂CH₂COOH → [-OCH₂CH₂CO-]ₙ + n H₂O (1 mark)
Repeat unit: -OCH₂CH₂CO- (1 mark)
Hydroxycarboxylic acid condenses (1 mark)

Question 7

In a landfill, how does light degrade some polymers? [2 Marks]

Answer 7

Light breaks bonds, forms radicals (1 mark)
Polymer fragments, more degradable (1 mark)

Question 8

Deduce the polymerisation type for [-OCH₂CH₂OCOCH₂CH₂CO-]ₙ and name it. [2 Marks]

Answer 8

Condensation, ester links (1 mark)
Polyester from diol + diacid (1 mark)

Question 9

Explain why polyesters degrade in acidic conditions. [2 Marks]

Answer 9

Ester bonds hydrolyse in H⁺ (1 mark)
Break into diol and diacid (1 mark)

Question 10

Analyse the formation of a polyamide from H₂NCH₂CH₂NH₂ + HOOCCH₂COOH vs. addition polymerisation. [3 Marks]

Answer 10

H₂NCH₂CH₂NH₂ + HOOCCH₂COOH → [-NHCH₂CH₂NHCOCH₂CO-]ₙ + H₂O (1 mark)
Condensation, releases H₂O (1 mark)
Addition: no byproduct, C=C opens (1 mark)

Question 11

Identify the monomers in [-NHCH₂CONHCH₂CO-]ₙ and predict its degradation. [2 Marks]

Answer 11

H₂NCH₂COOH (two units) (1 mark)
Biodegradable via hydrolysis (1 mark)