EFFECT OF CRYSTALLINITY ON THE INVIVO DEGRADATION OF POLY(BETA-PROPIOLACTONE) PREPARED BY RADIATION-INDUCED SOLID POLYMERIZATION IN ORGANIC-SOLVENT SYSTEM AT LOW-TEMPERATURE

Poly(β-propiolactone) [poly(PL)] samples with crystallinities of 32-67% were synthesized by radiation-induced solid polymerization at low temperature in the presence of various organic solvents. The crystallinity can be controlled by selection of solvent or by changing the content of solvent. This polymer which has an ester bond in the main chain degrades when implanted subcutaneously in the back of rats, e.g. a poly(PL) with crystallinity of 32% obtained by irradiating to 10 kGy at -78°C in a system containing of 12 ml of CCl4 and 1 ml of PL monomer was perfectly degraded in vivo in the 50th week from the start of the test, in contrast to only 16% for pure poly(PL) with crystallinity of 67%. This finding means that the biodegradability of poly(PL) is strongly dependent upon the crystallinity. The relationship between the biodegradability (y) of poly(PL) after 20 weeks implantation and the crystallinity (x) gave a good straight line, in which the regression line was found to be y = -1.701x + 120.6 and the correlation coefficient (r) was 0.985. © 1990.