Synthesis of aliphatic polyesters by a chain-extending reaction with octamethylcyclotetrasilazane and hexaphenylcyclotrisilazane as chain extenders

Aliphatic HO-terminated polyesters such as poly(diethylene glycol adipate) (PDEGA), poly(ethylene adipate) (PEA), and poly(butylene succinate) (PBS) with molecular weight from 1247 to 1948 were synthesized through condensation polymerization from adipic acid or butanedioic acid with excess diethylene glycol, ethylene glycol, or butylene glycol. From the HO-terminated polyesters, polyesters with high molecular weight were synthesized by a chain-extending reaction with octamethylcyclotetrasilazane (OMCT) or hexaphenylcyclotrisilazane (HPCT) as chain-extenders. Gel permeation chromatography (GPC) characterization shows that the M-n of chain-extended PDEGA is from 12,644 to 32,870, M-w is from 22,786 to 70,048; M-n of chain-extended PEA is 11,368, M-w is 19,877; and the M-n of chain-extended PBS is from 9823 to 39,873, M-w is from 18,823 to 137,192. The chain-extended polyesters were also characterized by H-1-NMR spectrum, IR spectra, and DSC spectra. The multiple peaks at 7.37 and 7.67 ppm in the H-1-NMR spectrum of chain-extended PDEGA and peaks at 3051.1 and 1593.4 cm(-1) in the IR spectrum of the chain-extended PBS show the evidence of the -SiPh2- structure in the polyesters obtained from the chain-extending reaction. DSC study shows that the bulky -SiPh2- units introduced by the chain-extending reaction lower the regularity of the polyester chains, so the melting point of the chain-extended PBS and PEA decreases compared to that of the original HO-terminated PBS and PEA. (C) 2004 Wiley Periodicals, Inc.