光敏性咖啡酸基三元聚酯的制备与自组装

Preparation and self-assembly of ternary polyesters based on 3,4-dihydroxycinnamic acid having photosensitivity

采用熔融缩聚方法合成了3,4-二羟基肉桂酸(DHCA,咖啡酸)、石胆酸(LCA)和聚乙二醇(PEG)的三元类嵌段共聚物P(DHCA-co-LCA)-b-PEG,用傅里叶红外变换(FTIR)光谱、核磁共振氢谱(1 H-NMR)和凝胶渗透色谱(GPC)对该聚酯的结构与分子量进行分析。所合成的聚酯结构,其分子量在2.0×104左右;差示扫描量热(DSC)、紫外光谱(UV)和荧光光谱对聚酯的热和光学性能,随着PEG投料量的增加,聚酯的玻璃化转变温度逐渐降低,荧光发射强度逐渐降低,在λ>310和254nm紫外光照射下可发生光交联和解交联反应,说明该聚酯具备一定的光可逆特性;该聚酯在选择性溶剂中可自组装形成表面光滑的球形胶束,平均直径约378nm,对不同波长的紫外光同样具有一定的响应性。

P(DHCA-co-LCA)-b-PEG polyesters were synthesized by polycondensation of 3,4-dihydroxycinnamic acid(DHCA,caffeic acid),lithocholic acid(LCA) and poly(ethylene glycol)(PEG).The structure and molecular weight of the P(DHCA-co-LCA)-b-PEG polyesters were characterized by Fourier transform infrared(FT-IR),nuclear magnetic resonance(1H-NMR) and gel permeation chromatography(GPC).The thermal and photosensitive properties of the polyesters were investigated by differential scanning calorimeter(DSC),UV spectroscopy and fluorescence spectroscopy.It is proved that glass transition temperature(Tg) and fluorescence emission intensity of the polyesters decreased when PEG increased in feed,but the fluorescence emission intensity of the polyesters obviously higher than DHCA monomer.P(DHCA-co-LCA)-b-PEG polyesters could be photo-crosslinked under λ>310nm UV light and its reversible photo-cleavage could take place under UV light of 254nm.The micelle nanoparticles were obtained by self-assembly at selective solvent.It was found that these nanoparticles have a nice spherical morphology with a smooth surface and possessed a certain photosensitivity based on the analysis of laser light scattering(LLS) and transmission electron microscopy(TEM).Their average diameter was about 378nm.