Particular examples of diluent comonomers include alkyl (alk)acrylate preferably containing 1 to 12, more preferably 1 to 4, carbon atoms in the alkyl group of the ester moiety, such as a methyl (alk)acrylate and butyl (alk)acrylate; a dialkylamino alkyl (alk)acrylate, preferably containing 1 to 4 carbon atoms in each alkyl moiety of the amine and 1 to 4 carbon atoms in the alkylene chain, e.g. 2(