Synthesis and characterization of poly(ethylene glycol)/poly(L-lactic acid) alternating multiblock copolymers
Synthesis and characterization of poly(ethylene glycol)/poly(L-lactic acid) alternating multiblock copolymers
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DOI：
10.1016/s0032-3861(98)00822-2
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发表时间：
1999-10-01
期刊：
影响因子：
4.6
通讯作者：
Bae, YH
中科院分区：
文献类型：
--
作者：
Huh, KM;Bae, YH
合成了由聚乙二醇（PEG）和聚l -乳酸（PLLA）组成的交替多嵌段共聚物热塑性水凝胶。采用l -乳酸在琥珀酸存在下的缩合反应合成了二羧基低聚聚乳酸。通过改变l -乳酸与琥珀酸的配比，控制PLLA的分子量。以双环己基碳二亚胺和n -二甲基氨基吡啶为催化剂，将PEG与二羧基-PLLA进行缩聚反应，得到了不同嵌段长度的PEG和PLLA交替多嵌段共聚物。采用h -1 nmr和FT-IR对二羧基plas和多嵌段共聚物的化学成分进行了表征，并用凝胶渗透色谱法测定了其分子量和分布。DSC热图显示，多嵌段共聚物中存在高度的相混合和微相分离，表现为非晶相混合区有较大的T-g峰，PLLA组分的结晶微畴有较小的T-m峰。低分子量嵌段共聚物具有水溶性，在较低的临界溶液温度（LCST）下呈云状。然而，高分子量聚合物在水中会膨胀，其光学透明度受温度的影响。这一观察结果可归因于温度升高引起的聚合物链中疏水部分之间疏水相互作用的增强。聚合物的重量膨胀比（吸收水/聚合物）受聚合物组成和分子量的控制。这些嵌段共聚物可能在药物输送和各种其他生物医学项目中提供潜在的应用。1999爱思唯尔科学有限公司版权所有。
Thermoplastic hydrogels of alternating multiblock copolymers, consisting of poly(ethylene glycol) (PEG) and poly(L-lactic acid) (PLLA), were synthesized. Dicarboxylated oligomeric PLLAs were synthesized by the condensation reaction of L-lactic acid in the presence of succinic acid. Changing the feed ratio of L-lactic acid to succinic acid controlled PLLA molecular weights. Alternating multiblock copolymers with different block lengths of PEG and PLLA were obtained from the polycondensation reaction between PEG and dicarboxylated-PLLA in the presence of dicyclohexyl carbodiimide and N-dimethyl aminopyridine as catalysts. The chemical compositions of dicarboxylated PLLAs and multiblock copolymers were verified by H-1-NMR and FT-IR, and the molecular weight and distribution were measured by gel permeation chromatography. DSC thermograms showed that there existed a high degree of phase mixing, as well as microphase separation in the multiblock copolymer, demonstrated by a large T-g peak from the amorphous phase-mixing domain and a small T-m peak from crystalline microdomains of the PLLA component. The block copolymers with low molecular weights were water-soluble and clouded at a temperature which is associated with a lower critical solution temperature (LCST) phenomenon. However, the high molecular weight polymers could swell in water and their optical transparency was influenced by temperature. This observation can be attributed to an enhanced hydrophobic interaction between hydrophobic moieties in the polymer chains, caused by an increase in temperature. The weight swelling ratio (absorbed water/polymer) of the polymers was controlled by polymer composition and molecular weight. These block copolymers may offer potential for applications in drug delivery and various other biomedical projects. (C) 1999 Elsevier Science Ltd. All rights reserved.