Photoinduced polymerization of bisimides as models for new soluble side-chain-substituted negative-type photosensitive polyimides

In this paper, we study the photoinduced polymerization of bisimide models for our new soluble side-chain-substituted negative-type photosensitive polyimides (PSPI) in order to better understand the polymerization behavior of the latter. These model compounds were cross-linked by UV irradiation in the solid state and in N-methyl-2-pyrrolidinone (NMP) solution. Variations in the molecular structure of the photosensitive moieties were explored to change the photosensitivity of models and of polymers. The kinetics of photopolymerization of these bisimide models was investigated by using infrared and UV techniques. The cinnamate and furylacrylate derivatives were found mainly to photodimerize, whereas the two others, acrylate and methacrylate derivatives, photopolymerize. Reaction orders of 1.5 and 2.0 were verified in the case of models but could not be determined for the polymers, due to the restriction of mobility of the photosensitive side groups on the polymer chains (solid-state irradiation) and also because the cross-linked polymer was no longer soluble in NMP and precipitated as it was formed.