In situ observation of azobenzene isomerization along with photo-induced swelling of cross-linked vesicles by laser-trapping Raman spectroscopy
In situ observation of azobenzene isomerization along with photo-induced swelling of cross-linked vesicles by laser-trapping Raman spectroscopy
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DOI：
10.1039/c2sm25963j
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发表时间：
2012-08
期刊：
影响因子：
3.4
通讯作者：
Guangyong Shen;Guosheng Xue;Jun Cai;Gang Zou;Yin-mei Li;Min-Cheng Zhong;Qi-jin Zhang
中科院分区：
文献类型：
--
作者：
Guangyong Shen;Guosheng Xue;Jun Cai;Gang Zou;Yin-mei Li;Min-Cheng Zhong;Qi-jin Zhang
采用激光捕获拉曼光谱（LTRS）检测单个囊泡交联膜中偶氮苯的光诱导异构化，该囊泡首先由两亲性共聚物自组装， 聚(N-异丙基丙烯酰胺)-嵌段-聚{6-[4-(4-吡啶偶氮)苯氧基]甲基丙烯酸己酯}(PNIPAM-b-PAzPy6)，然后通过共聚物链中的1,3-二溴丙烷和吡啶基团之间的反应进行交联。本研究工作中为了满足不同柔软度的囊泡的需要，制备了一系列不同交联度的聚合物囊泡。交联度为 0.0% 和 18.7% 的囊泡具有特征性的光诱导膨胀-收缩，而其他交联度较高的囊泡则没有。通过 LTRS 原位观察到偶氮苯的异构化以及不同交联度的单个囊泡的光诱导膨胀。对所得拉曼光谱的分析结果表明，偶氮苯的光致异构化是光致溶胀过程的触发因素，溶胀程度主要取决于交联程度，即聚合物囊泡的柔软度。前一个结果与囊泡溶液的紫外-可见光谱分析得到的结果不同，表明光致溶胀-收缩囊泡可以由少数带有偶氮苯单元的两亲性共聚物构建。
Laser-trapping Raman spectroscopy (LTRS) is adopted to detect the photo-induced isomerization of azobenzene in the cross-linked membrane of a single vesicle, which is self-assembled first by an amphiphilic copolymer, poly(N-isopropylacrylamide)-block-poly{6-[4-(4-pyridyazo)phenoxy]hexylmethacrylate} (PNIPAM-b-PAzPy6), and then cross-linked by reaction between 1,3-dibromopropane and pyridine groups in the copolymer chain. A series of polymer vesicles with different cross-linking degrees were made to meet the need of vesicles with different softness during this research work. Vesicles with 0.0% and 18.7% cross-linking degrees have characteristic photo-induced swelling–shrinking, others with higher cross-linking degrees do not. The isomerization of azobenzene is observed in situ by LTRS along with photo-induced swelling of single vesicles with different cross-linking degrees. Results from analysis of the obtained Raman spectra show that photo-induced isomerization of azobenzene is a trigger of the photo-induced swelling process and the swelling degree is mainly dependent on the degree of cross-linking, namely, the softness of the polymer vesicle. The former result is different from that obtained by analysis of UV-Vis spectroscopy for vesicle solutions and shows that photo-induced swelling–shrinking vesicles can be constructed by amphiphilic copolymers bearing azobenzene units in the minority.