STRUCTURE - Tg RELATIONSHIP IN POLYIMIDES.

Abstract

The Tg of polyimides is lowered by a decrease in the rigidity of the chain through the introduction of flexibilizing linkages, or by a reduction of interchain interactions. The interchain interactions in polyimides are charge transfer complexes whose strength is dependent on the electron affinity of the dianhydride and the ionization potential of the diamine. Charge transfer complex formation can be minimized, most effectively, by the introduction of 'separator' groups in the dianhydride which reduce its electron affinity, or by the use of meta diamines which distort the polyimide chain and interfere with chain packing.