Fu Dengwei, Li Juntao, Wei Jie, Guo Jinbao
College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China.
Soft Matter. 2015 Apr 21;11(15):3034-45. doi: 10.1039/c5sm00128e.
A novel series of photoresponsive chiral switches are fabricated by a facile hydrogen-bonded (H-bonded) assembly method, in which the binaphthyl azobenzene molecule is used as the proton acceptor, and binaphthyl acids with opposite chiral configuration are proton donors. We find that the helical twisted power of H-bonded chiral switches and the helical handedness of induced chiral nematic liquid crystals (N*-LCs) are mainly determined by the terminal flexible chain length in proton donors of binaphthyl acids. Controlling the lengths of the terminal flexible chain leads to different photoswitching behaviors by light irradiation, such as a helical inversion in the N*-LCs and a phase transition from N*-LCs to nematic LCs. This is mainly because of chiral counteraction and intensity attenuation of opposite chiral configurations between the proton acceptor and proton donor during UV-vis irradiation. Additionally, the thermal switching behavior of N*-LCs doped with H-bonded chiral switches is also demonstrated, and the related tuning mechanism may be attributed to the H-bonded effect and the changes in a dihedral angle of the binaphthyl rings. This facile assembly approach provides a new way for the fabrication of functional chiral switches for photonic applications.
通过一种简便的氢键组装方法制备了一系列新型的光响应手性开关，其中联萘基偶氮苯分子用作质子受体，具有相反手性构型的联萘酸用作质子供体。我们发现，氢键手性开关的螺旋扭曲能力和诱导手性向列相液晶（N* - LCs）的螺旋手性主要由联萘酸质子供体中的末端柔性链长度决定。控制末端柔性链的长度会导致光照下不同的光开关行为，例如N* - LCs中的螺旋反转以及从N* - LCs向向列相液晶的相变。这主要是由于紫外 - 可见光照期间质子受体和质子供体之间相反手性构型的手性反作用和强度衰减。此外，还展示了掺杂有氢键手性开关的N* - LCs的热开关行为，相关的调节机制可能归因于氢键效应和联萘环二面角的变化。这种简便的组装方法为制备用于光子应用的功能性手性开关提供了一种新途径。
