A NEW PHOTODEGRADABLE POLYAMIDE CONTAINING O-NITROBENZYL CHROMOPHORE STEADY-STATE AND LASER FLASH-PHOTOLYSIS STUDIES

A new photodegradable and thermally stable polyamide containing a photosensitive o-nitrobenzyl chromophore (4) was prepared by melt condensation of 4-alpha-methylamino-3-nitro-p-toluoyl chloride (5). On photolysis, 4 undergoes efficient photodegradation and becomes soluble in methanol and aqueous base, whereas the unirradiated polymer is insoluble in both solvents. This solubility difference renders the polymer 4 a potential material for microelectronic applications. The progress of photodegradation can be monitored by measuring the inherent viscosity of the polymer as a function of the irradiation time. The photodegradation pathway of 4 was studied by examining both steady state and laser flash photolysis of a low-molecular-weight model compound, 4-N-benzoyl-alpha-methylamino-3-nitro-N',N-dimethyl-p-tolumide (6). Steady state irradiation of 6 in methanol gives a mixture of N-methylbenzamide (10) and an azobenzenedicarboxylic acid 8. The transient species with an absorption maximum around 440 nm, produced from 6 on photolysis using 20 ps flashes of 355 nm laser light or 10 ns flashes of 308 nm laser light, is attributed to the nitronic acid 12. The formation of 12 is suggested to occur through a very fast singlet route and a slower triplet route.