Vertical alignment of liquid crystals using an in situ self-assembled layer of an amphiphilic block copolymer

We have employed an in situ self-assembled layer of an amphiphilic block copolymer to vertically align liquid crystals (LCs). The amphiphilic block copolymer used consisted of hydrophobic polyethylene (PE) and hydrophilic polyethylene glycol (PEG). The degrees of vertical alignment obtained for various PEG contents and polymer concentrations were compared through polarized optical microscopy, electro-optical measurements, and contact angle measurements. The LC cell prepared using a PEG content of 50% and concentration of 0.05 wt% exhibited the most uniform vertical alignment. Moreover, the electro-optical characteristics of this LC cell were similar to those of a conventional LC cell fabricated using a polyimide alignment layer. This was because the anchoring force for a PEG content of 50% was sufficiently high, allowing for uniform alignment. Since the proposed method involves only the simple doping of a low-concentration (0.05 wt%) amphiphilic block copolymer, it is also cost effective.