Abstract
Drying and imidization of PMDA–ODA solutions in NMP were investigated by a novel custom designed measurement system that tracks real time weight, thickness, surface temperature, and in-plane and out-of-plane birefringence. At low temperature drying stage, the weight and thickness reductions occurred rapidly as a result of solvent evaporation. All the parameters started leveling off while the out of plane birefringence steadily increased and reached a plateau at longer drying times. When the temperature was increased for imidization reaction, additional weight loss accompanied by temporary reduction of birefringence was observed due to evaporation of bound solvent as solvent molecules decomplexed from the polymer chains and plasticized the film. During the latter stage, out-of-plane birefringence rose rapidly due to increased intrinsic birefringence of the polymer chains due to imidization reaction and orientation of polymer chains with their chain axes preferentially oriented in the film plane. Throughout...
Published Version
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