Photoresponsive Carbohydrate-based Giant Surfactants: Automatic Vertical Alignment of Nematic Liquid Crystal for the Remote-Controllable Optical Device

Photoresponsive carbohydrate-based giant surfactants (abbreviated as CELA(n)D-OH) were specifically designed and synthesized for the automatic vertical alignment (VA) layer of nematic (N) liquid crystal (LC), which can be applied for the fabrication of remote-controllable-optical devices. Without the conventional polymer-based LC alignment process, a perfect VA layer was automatically constructed by directly adding the 0.1 wt % CELA(1)D-OH in the N-LC media. The programmed CELA(1)D-OH giant surfactants in the N-LC media gradually diffused onto the substrates of LC cell and self-assembled to the expanded monolayer structure, which can provide enough empty spaces for N-LC molecules to crawl into the empty zones for the construction of VA layer. On the other hand, the CELA(3)D-OH giant surfactants forming the condensed monolayer structure on the substrates exhibited a planar alignment (PA) rather than a VA. Upon tuning the wavelength of light, the N-LC alignments were reversibly switched between VA and PA in the remote-controllable LC optical devices. Based on the experimental results, it was realized that understanding the interactions between N-LC molecules and amphiphilic giant surfactants materials for the automatic LC aligninent.