Qin Lang, Gu Wei, Chen Yingying, Wei Jia, Yu Yanlei
Department of Materials Science, State Key Laboratory of Molecular Engineering of Polymers, Fudan University 220 Handan Road Shanghai 200433 China
RSC Adv. 2018 Nov 19;8(68):38935-38940. doi: 10.1039/c8ra07657j. eCollection 2018 Nov 16.
Light-driven chiral switches have the ability to tune and control the self-organized helical superstructures of cholesteric liquid crystals (CLCs), resulting in the photo-induced reflection wavelength shift of the CLCs. A new type of axially chiral switch functionalized with fluorine atoms to the azobenzene moiety is found to exhibit reversible visible-light-driven photoisomerization due to a separation of the n-π* absorption bands of the and isomers. These chiral switches all have high HTP values and the doped CLCs with 15.8 wt% concentration demonstrates reversible dynamic tuning of the reflection color within the entire visible spectrum driven by 530 nm and 445 nm visible light. It is also noteworthy that the thermal stability is improved thanks to the form of the fluorinated azobenzenes possessing a remarkably long half-life. The newly designed visible-light-driven chiral switches may broaden the application of CLCs, especially in the fields where high energy UV light is unfavorable.
光驱动手性开关能够调节和控制胆甾相液晶（CLC）的自组装螺旋超结构，从而导致CLC的光致反射波长发生偏移。人们发现一种新型的轴向手性开关，其在偶氮苯部分用氟原子进行了功能化，由于反式和顺式异构体的n-π*吸收带分离，该开关表现出可逆的可见光驱动光异构化。这些手性开关均具有较高的螺旋扭曲力（HTP）值，浓度为15.8 wt%的掺杂CLC在530 nm和445 nm可见光驱动下，在整个可见光谱范围内呈现出反射颜色的可逆动态调节。同样值得注意的是，由于氟化偶氮苯的反式结构具有非常长的半衰期，其热稳定性得到了提高。新设计的可见光驱动手性开关可能会拓宽CLC的应用范围，特别是在高能紫外光不利的领域。
