Polar anchoring strengths of nematic liquid crystal on high-density polymer brush surfaces

ABSTRACT

Herein, the polar anchoring energy coefficient (A_θ) of nematic liquid crystal (NLC) was examined for high-density polymer brushes via capacitance measurements. The A_θ is 10⁻⁴ J m⁻² for the brushes of poly(methyl methacrylate), poly(ethyl methacrylate) and poly(styrene). The value decreases to 10⁻⁵ J m⁻² for poly(n-butyl methacrylate) and poly(hexyl methacrylate) with lower glass transition temperatures. However, each polymer brush displays a constant A_θ value over a temperature range of −15°C to 90°C, which is hardly affected by the graft density and brush thickness. At 25°C, A_θ is 10 times greater than the corresponding azimuthal anchoring energy coefficient (A_φ); therefore, NLCs on polymer brushes can be preferentially aligned along the in-plane component of the applied field.

Graphical abstract

KEYWORDS:

• Nematic liquid crystal
• polar anchoring strength
• polymer brush
• atom transfer radical polymerisation
• capacitance–voltage curve

Acknowledgments

The authors greatly appreciate Dr. Fumito Araoka and Dr. Satoshi Aya (RIKEN), and Dr. Osamu Sato (LG Japan Laboratry) for their support on experiments and helpful discussion on this research.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental material

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Additional information

Funding

This work was supported by JST Strategic Promotion of Innovative Research and Development [Grant Number JPMJSV0915], Japan.