Photochemical behavior of poly(organophosphazenes). X. Photo-cross-linking phenomena in poly[bis(4-isopropylphenoxy)0.8 (4-benzoylphenoxy)1.2 phosphazene]

The synthesis and photochemical behavior both in solution and in the solid state of polybis(4-isopropylphenoxy)_0.8 (4-benzoylphenoxy)_1.2 phosphazene] is described. The main reaction of this material under illumination with light of a wavelength longer than 340 nm is the intramolecular abstraction of an hydrogen atom by the excited benzophenone substituent from the 4-isopropylphenoxy moiety geminally substituted on the same phosphorus of the phosphazene chain. In this way highly reactive radical species are produced which induce very efficient photo-cross-linking of the phosphazene copolymer and insolubilization. The efficiency of this process in the solid state is examined in view of the potential application of this material as a polyphosphazene-based negative photoresist.