Photochemical behaviour of POF-Part VIII. Further investigation on the sensitized photochemistry of poly[bis-(4- isopropylphenoxy)phosphazene].

The photochemistry of poly[bis(4-isopropylphenoxy)phosphazene] (PIPP) sensitized by hexakis(4-benzoylphenoxy)cyclophosphazene and by poly[bis(4-benzoylphenoxy)phosphazene] was investigated both in solution and in film. Air-equilibrated CH2Cl2 solutions of this polymer, also containing the above-mentioned benzophenone-containing phosphazene substrates, were irradiated with light absorbed exclusively by the carbonyl substituent. The irradiation causes a sharp decrease of the viscosity, attributed to chain scission of the PIPP backbone. In this process the solvent plays a key role. On the other hand, no photochemical change was observed for the same pair of molecules in the solid state. X-ray diffraction studies and DSC investigations on PIPP films, doped with benzophenone-substituted cyclo- or poly-phosphazenes, reveal that the lack of photoreactivity is due to phase segregation in these systems.