Photoalignment repeatability of azobenzene sulfonic films
As a liquid crystal photooriented material,azobenzene sulfonic SD1 has the advantages of non-contact,strong anchoring and reorientation,etc.In this paper,the photooriented writing performance of SD1 thin film of azobenzene sulfonic acid was studied under 405 nm linearly polarized light.It is found that the saturation degree of SD1 film decreases continuously with the increase of the number of repeated erasings.After 200 times of repeated erasings(Cumulative energy 1 200 J/cm2),the saturation degree(S)decreases from 0.78 to 0.3,and the orientation velocity decreases from 0.39 s-1 to 0.08 s-1.Furthermore,the UV-Vis absorption spectrum of SD1 film during the repeated orientation process was monitored in real time.It is found that the peak absorbance of UV-Vis absorption spectrum of SD1 film decreases rapidly,then slowly rises and reaches saturation during single orientation,and the overall absorption shows a trend of decreasing.After 200 reorientations,the absorption of SD1 film was gradually reduced,and the absorbance decreased from 0.10 to 0.03.This indicates that the number of trans SD1 molecules in the plane decreases during reorientation,resulting in a decrease in orientation ability,and thus a limited number of overwrites.After turning off the light source for a period of time,the number of molecules in the surface increased to a certain extent.To sum up,the number of in-plane molecules in SD1 films continues to decline during the process of repeated erase by online polarized light.Since the number of in-plane molecules in SD1 films directly affects its orientation ability,this partially reversible change in in-plane molecule number leads to limited SD1 repeatable orientation ability.
万方数据
维普
