A NEW SERIES OF TYPE-II (BENZOPHENONE) POLYMERIC PHOTOINITIATORS

Polyimides derived by the reaction of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) with amino-terminated polyethers have been used as photoinitiators in conjunction with tertiary amine synergists for the polymerization of acrylates. The performance of the new, fully characterized materials was compared with that of benzophenone and BTDA. The performance of the novel photoinitiators was assessed by their ability to cure thin films of multifunctional acrylates. Real time IR spectroscopy and photo-differential scanning calorimetry were used to assess the cure rate and extent of photopolymerization. Cured films were subjected to solvent extraction to determine the level and nature of the extractable components and these were shown not to contain any of the photoinitiator. The polyimide photoinitiators were found to be absent in the extracts. The polymeric photoinitiators were shown to have lower reactivities than benzophenone and BTDA. The reactivity of the new photoinitiators is affected by such factors as the composition of the polyimide and molecular weight (which markedly changes the viscosities of the formulations).