Glass transition temperatures of poly(itaconic acid ester)s containing pendant cycloalkyl rings

A series of poly(itaconic acid ester)s with pendant cycloalkyl rings, ranging in size from cyclopropyl to cyclododecyl, have been prepared. Two distinct groups have been synthesized; Group I derivatives have the ring attached directly to the main chain through an oxycarbonyl group and Group II polymers have a methylene unit inserted between the ring and the oxycarbonyl group. The glass transition temperatures, T_g, have been measured for polymers in each group. In Group I, T_g increased with ring size up to the dicyclohexyl derivative, but it then decreased with further increase in ring size. The decrease in T_g is due to the inherent flexibility of the ring which leads to internal plasticization of the sample. This effect appears to predominate over ring size in determining the magnitude of T_g, for 7–12 membered rings. Similar trends have been found in the Group II polymers, but the effect of the ring becomes less important the further it is moved away from the chain backbone.