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Updated: Jan 20, 2026

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Surface anchoring of nematic liquid crystal on swollen polymer brush studied by surface forces measurement
Takuya Yanagimachi1, Xiao Li2, Paul F Nealey2
1Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA; Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai, Miyagi 980-8577, Japan; Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai, Miyagi 980-8577, Japan.
Abstract:
Surface anchoring plays a fundamental role in controlling the molecular alignment of a bulk liquid crystal (LC). It has been previously shown that the pretilt angle of a nematic liquid crystal (NLC) can be controlled by changing the grafting density of a liquid crystalline polymer, poly(6-(4-methoxy-azobenzene-4'-oxy) hexyl methacrylate) (PMMAZO). In this study, the thickness of the swollen PMMAZO brush was measured by employing the surface forces apparatus (SFA). NLC 4-cyano-4'-pentylbiphenyl (5CB) and toluene were used as the solvents. It was shown that both 5CB and toluene were good solvents for PMMAZO. The repulsive force in 5CB appeared at D0 = 98.2 ± 4.6 nm for high grafting density (HD) surfaces, and at 32.1 ± 4.5 nm for the low grafting density (LD) surfaces. These results indicated that the PMMAZO molecules extended nearly perpendicular to the HD surfaces, while they laid on the substrate for the LD surfaces. The interaction between 5CB and the mesogenic group of PMMAZO was stronger than that for toluene. These results could support the expected surface anchoring mechanism of 5CB by the PMMAZO brush.
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