Poly-DL-lactic acid: polyethylene glycol block copolymers. The influence of polyethylene glycol on the degradation of poly-DL-lactic acid.
Poly-DL-lactic acid: polyethylene glycol block copolymers. The influence of polyethylene glycol on the degradation of poly-DL-lactic acid.
复制标题
DOI：
10.1163/156856294x00121
复制
发表时间：
1994
期刊：
影响因子：
--
通讯作者：
S. S. Shah-S.;K. Zhu;C. G. Pitt
中科院分区：
文献类型：
--
作者：
S. S. Shah-S.;K. Zhu;C. G. Pitt
ABA block copolymers of polyethylene glycol and poly-DL-lactic acid were prepared by ring-opening polymerization of DL-dilactide with alpha,omega-dihydroxy polyethylene glycol, Mn 1000 or 2000. The morphology of the resulting copolymers, with PEG:PLA ratios(mol/mol) of 1:2, 1:3 and 1:4, was characterized by DSC and ESR spectroscopy. The rate of water uptake was biphasic, reflecting the contribution of two processes: rapid diffusion of water into the initially miscible PEG and PLA blocks; then a slower rate of hydration possibly due to phase separation and hydrolytic cleavage of the PLA blocks. The rate of hydrolytic degradation of the block copolymers in DI water at 37 degrees C was measured by two methods: weight loss and colorimetric analysis of the carboxy end group concentration resulting from chain scission of PLA blocks. As a result of phase separation, the rate of scission of PLA blocks in the copolymers was similar to that of the PLA homopolymer. The more rapid onset of weight loss of the copolymers, relative to PLA, is attributed to the greater water solubility of PEG-PLA oligomers and their greater diffusivity in the more highly hydrated copolymers.
