Temperature sensitive polymers with pendant dimethyl maleinimide side groups were prepared by the copolymerization of N-isopropylacrylamide (NIPAAm) with varying amounts of a functional N-substituted acrylamide (2-(dimethyl maleinimido)-N-ethylacrylamide, DMIAAm). The polymers were characterized by H-1-NMR, IR, DSC and TGA. Their relative reactivity ratios have been determined. Aqueous solutions of the copolymers showed lower critical solution temperature behaviour (LCST). The phase transition temperatures of the aqueous solutions of these copolymers decreased with increasing comonomer content and disappeared at DMIAAm contents at or above 15.9 mol-%.