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

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 degrees 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 degrees 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. (C) 2011 The Japan Society of Applied Physics