Fabrications and Properties of Colorless Polyimide Films Depending on Various Heat Treatment Conditions via Crosslinkable Monomer

Poly (amic acid) (PAA) was prepared by reaction of bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetra-carboxylicdianhydride(BTDA) containing double bond for crosslinking and bis[4-(3-aminophenoxy)phenyl] sulfone(BAPS) in N,N-dimethylacetamide(DMAc). The cast film of PAA was heat-treated at different temperatures to create polyimide (PI) films. With increasing thermal crosslinking temperatures from 250 to 350 degrees C. the thermo-mechanical properties. degree of crosslinking, and optical transparency of the cross-linked PI were investigated. The maximum enhancement in the thermo-mechanical properties was observed at a heat treatment condition of 350 C. However. the optical transparency was found to be optimal for 250 E heat treatment. The degree of crosslinking in NMR was determined to be 85% to 93% with increasing annealing temperature conditions from 250 to 350 degrees C.