Seppälä Jukka V, Helminen Antti O, Korhonen Harri
Helsinki University of Technology, Department of Chemical Technology, Laboratory of Polymer Technology, P.O. Box 6100, FIN-02015 HUT, Finland.
Macromol Biosci. 2004 Mar 15;4(3):208-17. doi: 10.1002/mabi.200300105.
The major route to convert lactic acid to high-molecular-weight polymers is ring-opening polymerization of lactide. We have investigated alternative synthesis routes based on oligomerization and chain linking to produce high-molecular-weight thermoplastic degradable polymers cost-effectively. Chain linking also offers new possibilities to prepare degradable polyesters for biomedical applications by extending the range of polymer properties achievable. In this paper, we briefly review different chain linking techniques used in our laboratory. Typically, lactic acid prepolymers with molecular weights of around 3,000-15,000 g x mol(-1) have been prepared by direct polycondensation. Hydroxyl terminated oligomers have been chain linked by using diisocyanate coupling agents, preferably 1,4-butane diisocyanate, forming poly(ester-urethanes). Poly(ester-amides) have been prepared by using 2,2'-bis(2-oxazoline) as coupling agent for carboxylic acid telechelic oligomers. Chain linking by end functionalization has been used in the preparation of poly(ester-anhydrides). In addition, a variety of crosslinked degradable polymers and copolymers have been synthesized through different crosslinking routes, by using methacrylic, itaconic or maleic double bonds or triethoxysilane moieties. A biodegradation test and ecotoxicological evaluation of the degradation products were carried out in addition to hydrolysis tests. Lactic acid based chain linked polymers were biodegradable and the degradation products were harmless. In hydrolysis tests, enzymatic degradation was pronounced in the chain linked poly(epsilon-caprolactone).
将乳酸转化为高分子量聚合物的主要途径是丙交酯的开环聚合。我们研究了基于低聚和链连接的替代合成路线，以经济高效地生产高分子量热塑性可降解聚合物。链连接还为通过扩展可实现的聚合物性能范围来制备用于生物医学应用的可降解聚酯提供了新的可能性。在本文中，我们简要回顾了我们实验室中使用的不同链连接技术。通常，通过直接缩聚制备了分子量约为3000-15000 g·mol⁻¹的乳酸预聚物。羟基封端的低聚物通过使用二异氰酸酯偶联剂，优选1,4-丁烷二异氰酸酯进行链连接，形成聚（酯-聚氨酯）。聚（酯-酰胺）通过使用2,2'-双（2-恶唑啉）作为羧酸遥爪低聚物的偶联剂来制备。通过末端官能化进行链连接已用于聚（酯-酸酐）的制备。此外，通过使用甲基丙烯酸、衣康酸或马来酸双键或三乙氧基硅烷部分，通过不同的交联路线合成了各种交联可降解聚合物和共聚物。除了水解试验外，还对降解产物进行了生物降解试验和生态毒理学评价。基于乳酸的链连接聚合物是可生物降解的，并且降解产物是无害的。在水解试验中，链连接的聚（ε-己内酯）中酶促降解明显。
