PBS and PBSA were irradiated with gamma up to a 400 kGy dose. Gel content appeared at approximately 100 kGy dose with a higher gel content for PBSA. Charlesby-Pinner analysis indicated that chains scission predominated over crosslinking. Dispersity was increased by branching, that increased molecular weight until gelation, and by chain scission that decreased molecular weight. Careful analysis of the chemical structure by NMR showed that new species appeared with irradiation and some species increased whereas other decreased with the increase in dose. The same species were present in PBS and PBSA and the same variation in species took place in both polymers. From NMR results a mechanism for PBS and PBSA chain scission was proposed. Thermal properties were affected by irradiation, especially crystallization temperature, that decreased significantly with the increase in dose. Mechanical properties were strongly decreased by irradiation and both polymers became fragile at relatively low doses.
1Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Delegación Coyoacán, C.P. 04510, CDMX, Mexico