SYNTHESIS AND ENZYMATIC DEGRADATION OF REGULAR NETWORK ALIPHATIC POLYESTERS

Regular network aliphatic polyesters were prepared from glycerol (Yg) and a series of various length aliphatic dicarboxylic acids (HOOC-(CH2 )(n-2)-COOH, n = 4-10, 12 and 14). Prepolymers prepared by melt polyco ndensation were cast from dimethylformamide solution and post-polymeri zed at 230 degrees C for various times to form a network. The resultan t films were transparent, flexible and insoluble in organic solvents. The degree of reaction (D-R) estimated from the infrared absorbance of -OH and >CH2 or drop CH groups increased with increasing post-polymer ization time and length of methylene chain. The heat distortion temper ature also increased with increasing post-polymerization time and was 55, 28, 15, 6, 0, -1, -5, 4 and 32 degrees C for Yg4, Yg5, Yg6, Yg7, Y g8, Yg9, Yg10, Yg12 and Yg14 post-polymerized for 4 h, respectively. W ide angle X-ray scattering patterns showed a distinct single diffracti on peak, suggesting some ordered structure due to the establishment of a regular network. Density, water absorption and weight loss by alkal i hydrolysis decreased with increasing methylene chain length. The enz ymatic degradation was estimated by weight loss of the network films i n a buffer solution of lipase at 37 degrees C. The films of Yg4, Yg5, Yg6 and Yg7 showed no weight loss, but the weight loss increased great ly for Yg8, Yg9 and Yg10, and then decreased abruptly for Yg12 and Yg1 4. This suggests that the enzymatic degradation is affected by network structure, which allows the lipase to penetrate, and by the concentra tion of the enzymatically degradable ester linkage.