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

A new photodegradable and thermally stable polyamide containing a phot osensitive o-nitrobenzyl chromophore (4) was prepared by melt condensa tion of 4-alpha-methylamino-3-nitro-p-toluoyl chloride (5). On photoly sis, 4 undergoes efficient photodegradation and becomes soluble in met hanol and aqueous base, whereas the unirradiated polymer is insoluble in both solvents. This solubility difference renders the polymer 4 a p otential material for microelectronic applications. The progress of ph otodegradation can be monitored by measuring the inherent viscosity of the polymer as a function of the irradiation time. The photodegradati on pathway of 4 was studied by examining both steady state and laser f lash photolysis of a low-molecular-weight model compound, alpha-methyl amino-3-nitro-N',N-dimethyl-p-tolumide (6). Steady state irradiation o f 6 in methanol gives a mixture of N-methylbenzamide (10) and an azobe nzenedicarboxylic acid 8. The transient species with an absorption max imum 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 attri buted to the nitronic acid 12. The formation of 12 is suggested to occ ur through a very fast singlet route and a slower triplet route.