两亲性嵌段共聚物合成及亲疏水链段质量比对自组装形貌的影响

Synthesis of Amphiphilic Block Copolymer and Effect of Mass Ratio of the Hydrophilic and Hydrophobic Segments on the Self-assembly Morphology

通过原子转移自由基聚合(ATRP)方法依次以丙烯酸叔丁酯和甲基丙烯酰氧乙基二茂铁甲酯为单体,以2-溴异丁酸乙酯为ATRP试剂合成了嵌段共聚物聚丙烯酸叔丁酯-聚甲基丙烯酰氧乙基二茂铁甲酯(PtBA-b-PMAEFc),再通过水解脱除叔丁基得到两亲性嵌段共聚物聚丙烯酸-聚甲基丙烯酰氧乙基二茂铁甲酯(PAA-b-PMAEFc)。通过氢核磁共振波谱(~1H-NMR)、凝胶渗透色谱(GPC)对分子的结构、分子量及其分布进行了表征,应用荧光分光光度计测定了聚合物的临界胶束浓度(CMC),通过动态光散射(DLS)、透射电子显微镜(TEM)等仪器研究了分子在水溶液中通过亲疏水作用的自组装行为。研究结果表明两亲性嵌段共聚物PAA-b-PMAEFc的亲疏水链段比例对聚合物在水溶液中的组装形态具有重要影响,当亲水链段和疏水链段质量比较高时,形成囊泡等球状聚集体;当亲水链段和疏水链段质量比较低时,组装体倾向于形成棒状结构。

Self-assembly is generally a spontaneous organization driven by non-covalent interactions including hydrogen bonds,Van der Waals forces and electrostatic force,leading to well-controlled nanostructures and materials.Among the building blocks for self-assembly,diblock copolymers with two segments containing different chemical groups could be applied to prepare multiple responsive materials,which have been widely used in a variety of fields covering adsorbents,catalysts,coatings,biosciences and materials science due to their microscopic dimensions and their responsiveness to specific stimuli.For example,by combining segments with pH-and temperature-responses,it is possible to form macromolecules that response to both temperature and pH.In this paper,amphiphilic block copolymer PAA-b-PMAEFc was obtained by hydrolysis of block copolymer PtBA-b-PMAEFc,which was synthesized by the atom transfer radical polymerization(ATRP)with t-butyl acrylate and 2-(methacryloyloxy)ethyl ferrocene-carboxylate as monomers and ethyl-2-bromoisobutyrate as ATRP agent.Proton nuclear magnetic resonance spectroscopy(1H-NMR)and gel permeation chromatograph(GPC)were used to characterize the chemical structure,molecular weight and molecular weight distribution.The critical micelle concentration(CMC)of the polymer was determined by fluorescence spectrophotometer.The self-assembly behaviors and structures of PAA-b-PMAEFc were investigated by DLS and TEM.The results showed that the proportion of the amphiphilic block copolymer PAA-b-PMAEFc had a significant effect on the assembly in aqueous solution.Vesicles and spherical aggregates form when the mass ratio of the hydrophilic and hydrophobic segments was high,while rod-like structure appeared when the segments mass ratio decreased.