Lin W J, Flanagan D R, Linhardt R J
Division of Pharmaceutics, College of Pharmacy, University of Iowa, Iowa City 52242.
Pharm Res. 1994 Jul;11(7):1030-4. doi: 10.1023/a:1018943622498.
The solid-state degradation of poly(epsilon-caprolactone) catalyzed by primary, secondary and tertiary alkylamines was investigated. The degradation process was monitored by weight loss and molecular weight change measured by gel permeation chromatography. Degradation studies were conducted at 37 degrees C in methanol solutions of the alkylamines. Primary alkylamines caused rapid weight loss (i.e., approximately 90% weight loss in 30 days) that depended on alkylamine concentration, molar ratio of alkylamine to poly(epsilon-caprolactone) monomer and alkyl chain length. The secondary alkylamines caused less rapid polymer weight loss (i.e., approximately 90%) weight loss within 80 days). One tertiary alkylamine (N,N-diisopropylethylamine) showed little catalytic effect while a bicyclic tertiary alkylamine (quinuclidine) was about as catalytic as the primary alkylamines. The degradation products isolated when primary alkylamines were used include both esters and amides indicating that nucleophilic attack by the alkylamines competed with the amine-catalyzed methanolysis reaction. Only ester moieties could be identified in the products from reactions containing secondary and tertiary alkylamines, which indicated that they acted as nucleophilic catalysts. All of the primary alkylamines reduced poly(epsilon-caprolactone) molecular weight from about 25,000 to 10,000 within 10 days after which the molecular weight of the remaining solid leveled off even though weight loss continued.
研究了伯、仲和叔烷基胺催化聚（ε-己内酯）的固态降解。通过重量损失和凝胶渗透色谱法测量的分子量变化来监测降解过程。在37℃下于烷基胺的甲醇溶液中进行降解研究。伯烷基胺导致快速的重量损失（即，在30天内约90%的重量损失），这取决于烷基胺浓度、烷基胺与聚（ε-己内酯）单体的摩尔比以及烷基链长度。仲烷基胺导致聚合物重量损失较慢（即，在80天内约90%的重量损失）。一种叔烷基胺（N，N-二异丙基乙胺）显示出几乎没有催化作用，而一种双环叔烷基胺（奎宁环）的催化作用与伯烷基胺相当。使用伯烷基胺时分离出的降解产物包括酯和酰胺，这表明烷基胺的亲核攻击与胺催化的甲醇解反应相互竞争。在含有仲和叔烷基胺的反应产物中只能鉴定出酯部分，这表明它们起到了亲核催化剂的作用。所有伯烷基胺在10天内将聚（ε-己内酯）的分子量从约25,000降低到10,000，此后即使重量损失仍在继续，剩余固体的分子量也趋于稳定。
