新型偶氮功能化两亲性嵌段共聚物的合成及其光响应行为

Synthesis and photo-responsive behavior of an novel azobenzene-functionalized amphiphilic copolymer

采用可逆加成-断裂链转移(RAFT)聚合法制备了以苯乙烯-马来酸酐交替共聚物(PSMA)与聚乙二醇甲基丙烯酸酯(MAPEG)组成的共聚物(PSMA-b-PMAPEG),经4-氨基偶氮苯(4-AAB)修饰得光响应性两亲性嵌段共聚物P(St-al-Ma/azo-MaIM)-b-PMAPEG。用红外光谱(FT-IR)、核磁共振(1 H NMR)、凝胶渗透色谱(GPC)对其结构进行表征。此共聚物在水中可自组装形成胶束,由透射电子显微镜(TEM)和动态光散射(DLS)表征可知胶束直径约100nm。用紫外-可见光谱法(UV-Vis)研究胶束溶液的吸光度随光照时间的变化;DLS和扫描电子显微镜(SEM)观察紫外光和可见光辐射对胶束粒径的影响,结果表明,胶束经365nm紫外光照射后,偶氮苯由反式结构转变成顺式结构,粒径增大;再经420nm可见光照射,偶氮苯结构又从顺式转变回反式,粒径减小到初始值。

An amphiphilic block copolymer based on poly(styrene-co-maleic anhydride)-b-poly(single-methoxypoly(ethylene glycol)methyl acrylate)(PSMA-b-PMAPEG),was synthesized by reversible addition fragmentation chain transfer radical(RAFT)polymerization,and was further modified by p-aminoazobenzene to form photo-responsive block copolymer P(St-al-Ma/azo-MaIM)-b-PMAPEG.The block copolymer was characterized by Fourier transform infrared spectroscopy(FT-IR),1 H nuclear magnetic resonance(1 H NMR),and gel permeation chromatography(GPC).Nanosized micelles were formed by self-assembly when the P(SMA/azoMaIM)-b-P(MAPEG)was dissolved in water solution.Transmission electron microscopy(TEM)and dynamic light scattering(DLS)measurements showed that the micelles were regularly spherical in shape with an average diameter of about 100 nm.The photo-responsive behavior of the copolymer was studied by UV-Vis spectroscopy,DLS and scanning electron microscopy(SEM).The UV-Vis spectroscopy indicates that the absorption peak at 360 nm decreased and the peak at 450 nm increased with increasing the irradiation time of 365 nm UV light,and the corresponding absorption peak recovered when the solution continued to be irradiated using 420 nm visible light.The DLS measurements indicated that the size of the micelles increased from about 100 to about300nm when they were exposed under 365 nm light,and the micelles' size decreased from about 300 to about100nm when the irradiation was changed to 420 nm visible light,and these results were confirmed by SEM measurements.The size change of the micelles under the irradiation with different wavelength was caused by the isomerization of azobenzene which changed from trans-form to cis-form by UV irradiation of 365 nm and recovered to trans-form by visible light irradiation of 420 nm.