A polymerisable ethylenically unsaturated macromonomer being the reaction product of: i) an adduct formed from the reaction of an unsaturated non-mineral oil reacted with an enophile having an acid, ester or anhydride moiety and ii) an ethylenically unsaturated monomer having a moiety reactive with the acid, ester or anhydride moiety of the enophile and iii) a chain extender material having at least two moieties reactive with the acid, ester or anhydride moiety of the enophile.