CIE Jun 2013 v2 Paper 4 Q8

Answers available below

Examiners For Use 16 In recent years there has been considerable interest in a range of polymers known as hydrogels. These polymers are hydrophilic and can absorb large quantities of water. (a) The diagram shows part of the structure of a hydrogel. CH CH2 HO CH2 CH2 CH CH2 CH CH2 C CH2 CH2 OH CH2 CH The hydrogel is formed from chains of one polymer which are cross-linked using another molecule. (i) Draw the structure of the monomer used in the polymer chains. (ii) State the type of polymerisation used to form these chains.(iii) Draw the structure of the molecule used to cross-link the polymer chains.UCLES 2013 9701/42/M/J/13<br /> Examiners For Use 17 (iv) During the cross-linking, a small molecule is formed as a by-product. Identify this molecule.[5] (b) Once a hydrogel has absorbed water, it can be dried and re-used many times. Explain why this is possible, referring to the structure on the opposite page.[2] (c) Not every available side chain in the polymer is cross-linked, and the amount of cross-linking affects the properties of the hydrogel. (i) The amount of cross-linking has little effect on the ability of the gel to absorb water. Suggest why this is the case.(ii) Suggest one property of the hydrogel that will change if more cross-linking takes place. Explain how the increased cross-linking brings about this change.[3] [Total: 10]UCLES 2013 9701/42/M/J/13 [Turn over<br /> 18 BLANK PAGEUCLES 2013 9701/42/M/J/13<br />

Show answer