The azimuthal anchoring coefficient A2 of a nematic liquid crystal (NLC) on high-density polymer brushes was investigated using the threshold voltage for the in-plane switching of LC cells consisting of polymer-grafted substrates. A2 was affected by the bulk glass transition temperature (Tg) of the grafted polymers and decreased with increasing temperature. The NLCs on poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA) and poly(styrene) (PS) brushes had an A2 of 10−5 J m−2 at 25°C. In contrast, the NLC on a poly (hexyl methacrylate) (PHMA) brush exhibited a small A2 (1.1 × 10−6 J m−2) at 25°C and was oriented along the electrodes owing to the brush surface unevenness. With increasing temperature to 90°C, A2 of the NLCs on the PEMA and PS brushes decreased to the values of 10−7 J m−2, and the NLCs were oriented similar to the PHMA brush cell. Although the Tgs of PMMA and PS are similar, at 90°C the A2 of the NLC on the PMMA brush was 4.5 × 10−6 J m−2 and required a magnetic field for LC orientation. Such a difference in A2 is explained by the fact that PS has better compatibility with the NLC than PMMA.
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