NMR study of poly(gamma-glutamic acid) hydrogels prepared by gamma-irradiation: Characterization of bond formation and scission

Hydrogels were prepared from poly(gamma-glutamic acid) (PGA) solution by ga mma-irradiation of 90 kGy and 170 kGy. The hydrogels were more cross-linked with a higher dosage gamma-irradiation and completely hydrolyzed at 85 deg rees C within 4 hours resulting in homogeneous solution. NMR techniques wer e employed to clarify chemical bond formation and scission involved during gamma-irradiation and hydrolysis. Characterization of these samples was car ried out by taking both liquid state and solid state NMR spectra of PGA and hydrolyzed hydrogels and comparison of these spectra with the solid state NMR spectra of hydrogels. Our results indicate that complicated chemical bo nd formation and scission have occurred during hydrolysis and gamma-irradia tion. The samples prepared with higher dosage of gamma irradiation showed m ore diverse chemical bond formation and scission.