Alignment Control of Nematic Liquid Crystal using Gold Nanoparticles Grafted by the Liquid Crystalline Polymer with Azobenzene Mesogens as the Side Chains
Alignment Control of Nematic Liquid Crystal using Gold Nanoparticles Grafted by the Liquid Crystalline Polymer with Azobenzene Mesogens as the Side Chains
复制标题
以偶氮苯介晶为侧链的液晶聚合物接枝金纳米粒子对向列液晶的取向控制
DOI：
10.1021/acsami.8b07483
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发表时间：
2018-08-15
影响因子：
9.5
通讯作者：
Xie, He-Lou
中科院分区：
文献类型：
--
作者：
Kuang, Ze-Yang;Fan, Yao-Jian;Xie, He-Lou
采用两相Brust-Schiffrin方法，成功地设计并合成了以偶氮苯介生为侧链的液晶聚合物（LCP）高度接枝的金纳米粒子（表示为Au@TE-PAzo NPs）。单体和聚合物配体的化学结构用核磁共振证实，聚合物的分子量用凝胶渗透色谱测定。透射电镜和热重分析表明，纳米颗粒的粒径为2.5(+/- 0.4)nm， Au@TE-PAzo纳米颗粒中金的含量约为17.58%。所得Au@TE-PAzo NPs能很好地分散在5CB的向列相LC中。在适当的掺杂浓度下，分散良好的混合物可以在LC电池中自动形成完美的各向同性排列。各向同性排列归因于Au@TE-PAzo NPs在衬底上形成的刷状，其中Au@TE-PAzo NPs从混合物逐渐扩散到衬底上。相反，纯侧链lcp不能产生5CB的垂直排列，这表明5CB的排列归因于纳米颗粒与接枝lcp的协同相互作用。此外，Au@TE-PAzo NPs具有优异的成膜性能，因为它们的外围是高密度接枝的lcp，可以通过旋转涂覆形成均匀的薄膜。所得到的薄膜还可以促使向列型5CB的自动垂直对准。此外，在紫外和可见光交替照射下，由于Au@TE-PAzo NPs周围的偶氮苯基的顺式光异构化，SCB的取向在垂直和随机方向之间可逆地切换。这些实验结果表明，这种纳米粒子在构建远程可控光学器件方面具有潜在的应用前景。
The gold nanoparticles highly grafted by a liquid crystalline polymer (LCP) with azobenzene mesogens as the side chain (denoted as Au@TE-PAzo NPs) are successfully designed and synthesized by the two-phase Brust-Schiffrin method. The chemical structures of the monomer and polymer ligands have been confirmed by nuclear magnetic resonance, and the molecular weight of the polymer is determined by gel permeation chromatography. The combined analysis of transmission electron microscopy and thermogravimetric analysis shows that the size of the nanoparticles is 2.5(+/- 0.4) nm and the content of the gold in the Au@TE-PAzo NPs is ca. 17.58%. The resultant Au@TE-PAzo NPs can well disperse in the nematic LC of 5CB. The well-dispersed mixture with appropriate doping concentrations can automatically form a perfect homeotropic alignment in the LC cell. The homeotropic alignment is attributed to the brush formed by Au@TE-PAzo NPs on the substrate, wherein the Au@TE-PAzo NPs gradually diffuse onto the substrate from the mixture. On the contrary, the pure side chain LCPs cannot yield vertical alignment of 5CB, which indicates that the alignment of 5CB is ascribed to the synergistic interaction of the nanoparticles and the grafted LCPs. Moreover, Au@TE-PAzo NPs show excellent film-forming property on account of their periphery of high densely grafted LCPs, which can form uniform thin film by spin-coating. The resultant thin film also can prompt the automatical vertical alignment of the nematic 5CB. Further, upon alternative irradiation of UV and visible light, the alignment of SCB reversibly switches between vertical and random orientation because of the trans-cis photoisomerization of the azobenzene group on the periphery of Au@TE-PAzo NPs. These experimental results suggest that this kind of nanoparticles can be potentially applied in constructing the remote-controllable optical devices.