POLYMETHACRYLATES WITH BENZYLIDENEPHTHALIMIDINE SIDE-CHAINS, 1 - PHOTOCHEMICAL CHARACTERISTICS OF MODEL COMPOUNDS AND POLYMERS

The photochemical behavior of polymers with benzylidenephthalimidine ( BPI) side chains is described, together with the photochemistry of low -molecular BPIs in solution. The stereochemistry of BPIs is critically influenced by their N-substituent; Z-isomer of BPI itself without N-s ubstituent is a thermally stable form, while E-isomer with a Z-stilben e skeleton is more thermally stable for N-substituted BPIs as a result of steric distortion due to repulsive interaction between the N-subst ituent and the benzylidene phenyl ring. UV irradiation of low-molecula r N-substituted BPIs and polymethacrylates with E-BPI side chains in s olution results exclusively in the En photoisomerization without any s ide reaction including photodimerization. Photoirradiation of thin fil ms of BPI polymers leads to photoisomerization at the early stage, fol lowed by the gradual decrease of absorption bands ascribable to BPI mo ieties as a result of [2+2] photodimerization, leading to insolubiliza tion. Quantum efficiencies for the photocrosslinking are much smaller, displaying that the photoisomerization is a predominant reaction even in solid films. Dichroism of the chromophores is induced by linearly polarized light irradiation of thin films of BPI polymers due to the p hotoisomerizability of BPI units. Further discussion is made on factor s affecting the photochemical behavior of BPI polymers.