SYNTHESIS of BIODEGRADABLE COLYMER OF LACTIC ACID HAVING THIOL GROUPS AND EVALUATION OF ITS CHARACTERIZATION

为改善聚乳酸[聚(LA)]的性质并在聚(LA)中引入侧链硫醇基团，通过开环和共聚L-乳酸、乙醇酸(GLC)和半胱氨酸(Cys)，然后脱去甲氧基苄基的保护，合成了L-LA、乙醇酸(GLC)和半胱氨酸(Cys)的无规三元共聚物{聚[LA-随机-(Glc-Cys)]}。通过改变(GLC-Cys)单元的摩尔分数，可以改变改性聚(LA)的溶解性、热转变、降解行为及其膜的水接触角。此外，为了实现硫醇基团在共聚物膜表面的高积累，本论文还研究了AB型L-丙交酯两嵌段共聚物(L-LA)与含侧基硫醇基团的去脂肽的合成。以乙醇钾为引发剂，在四氢呋喃(THF)溶液中聚合了环[GLS-Cys(MBzl)]。得到的聚[GLC-半胱氨酸(MBzl)]的末端羟基被K/N转化为醇钾。以醇盐为大分子引发剂，在四氢呋喃中聚合L-LA，得到具有两个熔融温度的聚[GLC-半胱氨酸(MBZL)]-嵌段聚乳酸。通过对甲氧基苄基的后续脱保护，得到了可生物降解的两亲性AB型嵌段共聚物-聚(GLC-半胱氨酸)-嵌段-聚合物。嵌段共聚物膜表面硫醇基团的积累能力高于无规共聚物膜。

To modify the properties of poly(lactic acid)[poly(LA)] and to introduce pendant thiol groups to poly(LA), the random terpolymer of L-LA, glycolic acid(Glc) and cysteine(Cys) {poly[LA-random-(Glc-Cys)]} was synthesized through ring-opening and copolymerization of L-lactide with cyclodepsipeptide cyclo{Glc-Cys(MBzl) and subsequent deprotection of methoxybenzyl groups. By changing the mol fraction of (Glc-Cys) unit, the solubility, thermal transition, degradation behavior of the modified poly(LA), and the water contact angle of its film could be varied. Moreover, to achieve high accumulation of thiol groups located on the surface of copolymer film, the synthesis of AB-type diblock copolymer of L-lactide (L-LA) and depsipeptide with pendant thiol groups were investigated. Cyclo[Gls-Cys(MBzl)] was polymerized in tetrahydrofran (THF) solution using potassium ethoxide as an initiator. The terminal hydroxyl group of the poly[Glc-Cys(MBzl)] obtained was converted to potassium alkoxide by K/naphthalene. L-LA was polymerized in THF using the polymer alkoxide as a macroinitiator to obtain poly[Glc-Cys(MBzl)]-block-polyLA showing two melting temperatures (Tms). Through subsequent deprotection of methoxybenzyl groups, the biodegradable amphiphilic AB-type block copolymer, poly(Glc-Cys)-block-polyLA, was obtained. The accumulation ability of thiol groups located on the surface of block copolymer film was evaluated to be higher than that of the random copolymer film.