Homeotropic orientation of nematic liquid crystals induced by dissolving polypropyleneimine dendrimer having peripheral mesogens

Abstract

A mixture of nematic liquid crystals (NLCs) with a small amount of a polypropyleneimine-based liquid crystalline dendrimer (D-6PC5 and D-6PPCN) exhibited spontaneous homeotropic alignment between the native glass substrates. This dendrimer-induced homeotropic alignment required two conditions; 1) the dendrimer completely dissolves in the NLC, and 2) a substrate surface is hydrophilic with the surface free energy above approximately 65 mN·m−1. The interdigitated-electrode cells without any surface treatment of the substrates were fabricated by filling with the LC dendrimer (D-6PC5)/nematic LC mixtures. They exhibited an electro-optical behavior when applying AC, vertical-alignment drive occurred in the cells. Based on these results, we speculated that the dendrimer adsorbs on the substrate surface and acts as a vertical alignment layer.