SRG Inscription in Supramolecular Liquid Crystalline Polymer Film: Replacement of Mesogens

Abstract

The photoinduced surface relief formation via mass transfer upon irradiation with patterned light has long been a subject of extensive investigation. In azobenzene-containing liquid crystalline materials, UV light irradiation that generates the cis isomer leads to the liquid crystal to isotropic photochemical transition. Due to this phase change, efficiency of the mass transfer to generate a surface relief grating (SRG) becomes markedly greater. We have previously indicated that azobenzene-colored SRG-inscribed film can be bleached by removing a hydrogen-bonded azobenzene mesogen. However, this process largely reduces the height feature of the SRG corrugation. Herein, we propose an extended procedure where a colorless mesogen is filled successively after the removal of the azobenzene side chain. The process involves four stages: (i) SRG inscription in a hydrogen-bonded supramolecular azobenzene material; (ii) crosslinking (insolubilization) of the SRG film; (iii) removal of azobenzene mesogen by rinsing with a solvent, and (iv) stuffing the hollow film with a different mesogen. Although the final stuffing stage was insufficient at the present stage, this work demonstrates the possibility and validity of the strategy of mesogen replacement.

Keywords

• azobenzene
• liquid crystalline polymer
• surface relief grating
• hydrogen bonding