High-Density Poly(methyl methacrylate) Brushes as Anchoring Surfaces of Nematic Liquid Crystals

Abstract

The orientation of a nematic liquid crystal (LC) on high-density poly(methyl methacrylate) (PMMA) brushes was examined. The nematic LC was injected into the cell consisting of two substrates on which PMMA chains were grafted with a density of 0.299 chains nm-2. It showed degenerate planar orientation, which became uniform on cooling from 120 °C at a magnetic field of 1 T. At ambient temperature, the aligned LC cell showed typical electro-optical properties when driven in the in-plane switching (IPS) mode, indicating that the LC molecules anchored to the brushes with the director parallel to the magnetic field direction. In contrast, at temperatures higher than 65 °C, the transmittance of the cell was time-dependent when driven over a prolonged period, suggesting that the anchoring direction rotated toward the electric field direction. Such temperature-dependent anchoring of the LC can be associated with the viscoelasticity of the PMMA brushes.