Performance‐improved photo‐driven liquid crystal cell using azobenzene‐grafted ladderlike polysiloxane as command layer

Abstract

AbstractIn comparison with our previous work1, the stability of the command layer based on an azobenzene‐grafted ladderlike copoly(hydromethylsilsesquioxane) (PMHSQ) coated on quartz plates, is improved evidently by linking through a coupling reagent (triethoxyvinylsilane) to the backbone. The liquid crystal (LC) cell filled with 4‐cyano‐4′‐pentylbiphenyl (5CB) exhibits a much faster switching behavior, so that activation is unnecessary. The results show that the photo‐driving behavior is strongly dependent on the nature of the LCs as well as the structure of the azobenzene (Az) side chains. The cyanobiphenyl type LC (5CB) with a strong polarity sandwiched between such two command layers changes the alignment between homeotropic and planar modes while TC3 (mainly phenylcyclohexanecarboxylates) with a weak polarity fails to do so. The Az units with longer spacer are more effective to induce changes of the LC alignment. It was found that the phenyl benzoates are not stable to ultraviolet (UV) irradiation and that they absorb the UV light strongly. Thus, we suppose that such negative aspects as the necessary activation and the slow response of our previously studied photo‐driven LC cell using commercial TEB‐30 (mainly cyanobiphenyls and phenyl benzoates as well) are caused by the phenyl benzoate components.