化学学报 ›› 2014, Vol. 72 ›› Issue (5): 602-608.DOI: 10.6023/A14010069 上一篇    下一篇

研究论文

不同亲疏水比例的光响应性嵌段共聚物的合成及溶液组装行为研究

丁妍春, 俞燕蕾, 韦嘉   

  1. 复旦大学材料科学系 上海 200433
  • 收稿日期:2014-01-23 出版日期:2014-05-14 发布日期:2014-03-29
  • 通讯作者: 韦嘉 E-mail:weijia@fudan.edu.cn
  • 基金资助:

    项目受国家自然科学基金(Nos. 21134003,21273048,51225304,51203023)、复旦大学中央高校基本科研业务费青年教师科研能力提升项目(No. 20520133189)和上海市自然科学基金(No. 12ZR1401600)资助.

Synthesis and Self-assembly Behavior of Photo-responsive Diblock Copolymers with Different Hydrophilic/Hydrophobic Ratios

Ding Yanchun, Yu Yanlei, Wei Jia   

  1. Department of Materials Science, Fudan University, Shanghai 200433
  • Received:2014-01-23 Online:2014-05-14 Published:2014-03-29
  • Supported by:

    Project supported by the National Natural Science Foundation of China (Nos. 21134003, 21273048, 51225304, 51203023), Fundamental Research Funds for the Central Universities (No. 20520133189) and Shanghai Natural Science Foundation (12ZR1401600).

以末端带有二硫代酯基团的聚合物PhC(=S)-S-PEO作为大分子链转移剂,利用可逆加成-断裂链转移自由基聚合法(RAFT)合成一系列亲疏水比例不同的嵌段共聚物PEOn-b-PMeA6AB2m,并采用核磁共振(1H NMR)和凝胶渗透色谱(GPC)对产物进行了表征. 运用场发射透射电子显微镜(FETEM)、扫描电子显微镜(SEM)、场发射扫描电子显微镜(FESEM)、光学显微镜、粒径分析仪和荧光光谱研究了聚集体的形貌、粒径及其在光刺激下的响应行为. 结果表明,聚集体形态为胶束,包含大复合胶束. 随着自组装初始浓度的降低、转速的增加,聚集体尺寸降低,分布趋于均一;当亲疏水比例为2.3时,球形复合胶束中出现了花生型、棒状结构. 包覆有尼罗红的聚集体在紫外/可见光的循环照射下,部分尼罗红被释放. 共聚物BCP-S3-0.82形成的自组装体系在紫外光照射下,尺寸较大的复合胶束发生一定程度的不可逆的解离.

关键词: 可逆加成-断裂链转移自由基聚合法, 两亲性嵌段共聚物, 偶氮苯基团, 亲疏水比例, 自组装, 胶束

A series of diblock copolymers, poly(ethylene oxide)-block-poly{6-[4-(4-ethoxyphenylazo) phenoxy] hexyl methacrylate} (PEO-b-PMA6AB2), with different hydrophilic/hydrophobic ratios were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The structures and properties of diblock copolymers were characterized by 1H NMR and gel permeation chromatography (GPC). The self-assembly method was as follows: block copolymers were dissolved in tetrahydrofuran (THF) at first, and then by adding water at the rate of 2.5 μL/s, the aggregates self-assembled when the critical micelle concentration (CMC) was reached. Field emission transmission electron microscope (FETEM), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), optical microscope, particle size analyzer, UV-Vis absorption spectroscope and fluorescence emission spectroscope were used to study the morphology and size of the aggregates and their stimuli-responsive behavior. The SEM and FETEM results showed that polymeric micelles and large compound micelles (LCM) coexisted in the aqueous solution. Furthermore, it was found that the size of the self-assembly reduced with the decrease of initial concentration and the increase of stirring rate, and the distribution tended to be uniform. Meanwhile, the morphology of large compound micelles turned to be different, changing from common sphere to peanut shape or rod-like shape when the hydrophilic/hydrophobic ratio was 2.3. By encapsulating Nile Red into the aggregates, the peanut shape and rod-like shape were captured by fluorescence microscope. UV-Vis absorption spectra of the self-assembly revealed that the photo-responsive behavior of azobenzene moieties in the aggregates was reversible but restricted to some extent. The change on fluorescence intensity of Nile Red encapsulated in the diblock copolymer aggregates indicated that the alternative irradiation of UV and visible light induced the release of Nile Red resulted from the photoisomerization of the azobenzene moieties. In addition, the photo-responsive study showed that large compound micelles self-assembled from BCP-S3-0.82 could dissociate under the irradiation of UV light. Other large compound micelles assembled from the rest of block copolymers also dissociated, but the extent of the dissociation was not as remarkable as BCP-S3-0.82, which had the maximal hydrophobic ratio.

Key words: RAFT, amphiphilic block copolymer, azobenzene moiety, hydrophilic/hydrophobic ratio, self-assembly, micelles