(a(i))[2]
Draw the structure of the monomer from which the polymer chains are formed.
(a(ii))[1]
State the type of polymerisation that forms these chains.
(a(iii))[2]
Draw the structure of the molecule that cross-links the polymer chains.
(a(iv))[5]
A small by-product molecule is formed during cross-linking. Identify this molecule.
(b)[2]
Once a hydrogel has taken in water, it can be dried and used again many times. Explain why this is possible, referring to the structure on the opposite page.
(c(i))
The extent of cross-linking has little effect on how well the gel absorbs water. Suggest a reason for this.
(c(ii))[3]
Suggest one property of the hydrogel that changes if cross-linking becomes more extensive. Explain how the greater cross-linking causes this change.