CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Langmuir. 2011 May 17;27(10):6330-7. doi: 10.1021/la200422q. Epub 2011 Apr 14.
We report on a new type of liquid crystalline cellulosic films with light controllable reversible wettability. The films are prepared from a thermotropic cellulose derivative functionalized with azo-containing groups. These groups exhibit dynamic changes in interfacial properties in response to UV irradiation. The UV irradiation induces trans-to-cis isomerization in the azobenzene moiety, which causes a conformational change in the upper molecular layers of the thin films. These changes originate a hydrophobic to comparatively hydrophilic transformation of the surface. The reversible wettability of the surface results from the cis/trans photo and thermal isomerization. The UV-vis absorption spectra, as well as contact angle measurements with UV irradiation, clearly support the understanding of the phenomenon. This type of surface design enables the amplification of molecular level conformational transitions to macroscopic changes in interface properties using the means of isomerism. This opens new opportunities in surface engineering using eco-friendly cellulose manipulation.
我们报告了一种新型的具有光控可逆润湿性的液晶纤维素薄膜。该薄膜由功能化的热致各向异性纤维素衍生物制备而成，其中含有偶氮基团。这些基团在界面性质上表现出动态变化，可对紫外光照射做出响应。紫外光照射会诱导偶氮苯部分发生顺反异构化，从而导致薄膜上层分子层的构象发生变化。这些变化会导致表面由疏水性向相对亲水性转变。表面的润湿性是可逆的，这是由于顺反异构化的光和热反应所致。紫外可见吸收光谱以及与紫外光照射相关的接触角测量结果，均清楚地支持了这一现象的理解。这种类型的表面设计能够利用异构化的手段，将分子水平的构象转变放大到界面性质的宏观变化上。这为使用环保型纤维素处理方法进行表面工程开辟了新的机会。
