Competitive Dye Adsorption-Desorption on the Isotropic Surface at the Early Stage of the Photoexcitation of Azo Dye-Doped Liquid Crystals

Crystals

Chia-Yi Huang¹  Shih-Hsuan Chen²  KuangYao Lo²  Sheng-Chung Ji²  Wei-Ting Chen² 

[1] Department of Applied Physics, Tunghai University, Taichung 407224, Taiwan;Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan;

关键词: azo dye;    liquid crystals;    photoexcitation;    in situ;    attenuated total reflection (ATR);    adsorption;   

DOI  :  10.3390/cryst10090802

来源: DOAJ

【 摘 要 】

The instantaneous response of liquid crystal (LC) molecules near the dye-adsorbed layer of azo dye-doped LCs (ADDLCs) in early-stage photoexcitation was observed through the pumped-attenuated total reflection (PATR) method. As the sensing depth of the attenuated total reflection (ATR) method is in the order of hundreds of nm, in situ observation using the PATR method directly inspected the restructuring of the adsorbed layer in the early-stage photoexcitation, which demonstrated the competition between adsorption and desorption on the isotropic surface without the interference of the elastic continuum in the bulk of a cell. Analyzing the frequency of the oscillation-like PATR signal, which reflects the evolution of the orientation of the LC molecules, revealed that, depending on the dose of the pump light, the structural evolution of the adsorbed layer is fast at the beginning of photoalignment in ADDLCs and slows down with the accumulation of the adsorbed layer. A suitable intensity of the pump light in the early stage of the photoalignment process can improve the reform of the adsorbed layer to strengthen its anchoring.

【 授权许可】

Unknown