GAMMA-IRRADIATION OF CHITOSAN

Chitosan has potential biomedical applications that may require the fi nal products to be sterilized before use. The gamma irradiation of pur ified and highly deacetylated chitosan fibers and films at sterilizing doses (up to 25 kGy) caused main chain scissions. The viscosity avera ge molecular weight of the polymer decreased with increasing irradiati on dose, the radiation yields of scission being 1.16 in air and 1.53 i n anoxia. Preirradiation application of a negative pressure of 100 kPa disrupted the network structure, which may have contributed to the gr eater radiation yield obtained by chitosan fibers in anoxia, Radiation induced scission of the chitosan chains resulted in a lower glass tra nsition temperature (T-g), indicative of higher segmental mobility, Th e T-g was below ambient at an irradiation dose of 25 kGy in air. Irrad iation in air improved the tensile strength of the chitosan him, proba bly due to changes in chain interaction and rearrangement. Irradiation in anoxia did not affect film properties significantly, partly becaus e the preirradiation application of negative pressure had a negligible effect an the structure of the chitosan film. Polymer network structu re and the irradiation conditions are therefore important determinants of the extent of radiation induced reactions in chitosan. (C) 1998 Jo hn Wiley & Sons, Inc.