Photopolymerization of Reactive Amphiphiles: Automatic and Robust Vertical Alignment Layers of Liquid Crystals with a Strong Surface Anchoring Energy

A photopolymerizable itaconic acid-based amphiphile (abbreviated as Ita3C₁₂) consisting of a hydrophilic carboxylic acid, three alkyl tails, and a reactive vinyl function was newly designed and synthesized for the formation of automatic and robust vertical alignment (VA) layer of nematic liquid crystals (NLC). Since a hydrophilic carboxylic acid was chemically attached to the end of Ita3C₁₂, the Ita3C₁₂ amphiphiles initially dissolved in the host NLC medium were migrated toward the substrates for the construction of VA layer of NLC. The alkyl tails of Ita3C₁₂ in the VA layer directly interacted with host NLC molecules and made them to automatically align vertically. Because of the reactive vinyl functions of Ita3C₁₂ amphiphiles, it was possible to stabilize the automatic VA layer by the photopolymerization with methacryl polyhedral oligomeric silsesquioxane (MAPOSS) cross-linkers. The polymer-stabilized robust Ita3C₁₂ VA layer exhibited a strong surface anchoring energy without generating any light scatterings. The automatic fabrication of robust LC alignment layers can allow us to reduce the manufacturing cost and to open new doors for electro-optical applications.