AB2星型杂臂共聚物的合成及其结晶行为

通过分子设计, 用过量丁二酸酐将单硬酯酸甘油酯的两个羟基转变为羧基, 再以辛酸亚锡为催化剂, 二苯醚为共沸脱水剂, 使其进一步与不同分子量的端羟基聚乙二醇在负压下共沸脱水偶联, 成功地制备了一系列AB2星型杂臂共聚物, 并采用1H NMR、XRD、DSC、FTIR和偏光显微镜等手段对产物及其结晶行为进行了研究. 1H NMR测试结果表明, 所得聚合物是以二丁二酸甘油酯为核, 一条硬酯酸烷基(GMS)臂和两条聚乙二醇(PEG)臂构成的AB2星型杂臂共聚物GMS-(SA-PEG)2]. DSC和XRD测试结果表明, 在GMS-(SA-PEG)2中, GMS臂和PEG臂都能结晶; GMS臂的存在不仅影响PEG臂的结晶速度, 同时也影响其结晶的完善程度, 导致结晶温度和结晶熔融温度发生变化; GMS臂相对含量越大, 对PEG结晶行为的影响也越大. 利用偏光显微镜对结晶过程的在线观察结果表明, GMS-(SA-PEG)2的结晶形貌不同于线型聚乙二醇的大球晶, 其先形成细碎的束状晶核, 然后逐步出现生长中的球晶结构, 最后所形成的晶体尺寸有大幅度的减小, 而且其形貌和PEG臂的分子量密切相关. 可见AB2星型杂臂共聚物的结晶是先由GMS臂结晶形成小晶核, 然后再诱导PEG臂球晶的生长. 杂臂的引入对于控制星型多臂共聚物的晶形、晶貌具有重要意义.

Synthesis of AB2 Star-shaped Miktoarms Copolymers and Their Crystallization Behavior

A small molecule(GMS-SA2) with one alkyl chain and two terminal carboxyl groups was synthesized successfully via the reaction of glyceryl monostearate with excessive succinic anhydride.Then,the small molecule was used as a coupling agent to condensate with polyethylene glycols(PEG) with different molecular weights or polyethylene glycol monomethyl ether(PEGm) in the presence of stannous octoate as the catalyst and diphenyl ether the as azeotropic agent to remove water.Thus,the AB2 star-shaped miktoarms copolymers were obtained successfully,and were characterized via 1H NMR,DSC,GPC,XRD,FTIR and micropolariscope,etc.DSC and XRD measurements indicate that the crystallizing temperature and the melting temperature of the AB2 star-shaped miktoarms copolymers were different from those of the corresponding linear PEGs because the existing of GMS-SA2 altered its crystallizing velocity and the perfect degree of crystal.It is very important to control the crystal shape of the star-shaped copolymers through introducing the miktoarms into the copolymers and changing its content in copolymers.