Configuration of a chiral smectic-C film with a circular inclusion : Pathological contribution of spontaneous bend?(Poster session 2, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

Abstract

キラルスメクチックC液晶からなる2次元薄膜中に円形のコロイド粒子が含まれる時の,液晶のc-ディレクタの構造,および粒子表面に生じる欠陥の配置を解析的に考察する.液晶のキラリティに起因する自発的な曲げ変形の存在により,キラルでないスメクチック液晶の場合に期待される四重極の対称性を持った構造とは異なり,より対称性の低い双極子の対称性を持った,表面欠陥を伴う構造が形成される.液晶の自由エネルギーを最小にする表面欠陥の位置は,自発的な曲げ変形の強さ,コロイド粒子の半径のみならず,液晶薄膜の外側の境界の形,および境界条件に(たとえ境界が無限遠にあっても)依存するという,直観的には理解しがたい結果が導き出される.上記の結果は,自発的な曲げ変形に関する自由エネルギーの寄与が原因となっている.

Colloidal dispersions with liquid crystal (LC) hosts have attracted great interest for the last decade, and recent attention has been focused on quasi-two-dimensional (2D) thin films with colloidal inclusions as well as three-dimensional systems. Here we consider a chiral smectic-C (SmC) LC film as the host fluid of the 2D colloidal system. Recently Dolganov et al. showed experimentally that the c-director profile of the chiral SmC film around a circular inclusion adopts dipolar rather than quadrupolar configuration observed in achiral SmC films. They also argued that it might be attributed to spontaneous bend inherent in 2D chiral LC systems. Later, Bohley and Stannarius carried out numerical calculations to show that the presence of the spontaneous bend term in the elastic energy of the c-director indeed brings about dipolar configurations. The aim of the present study is to give an analytic argument on how spontaneous bend influences the c-director configuration and the position of surface defects in a chiral SmC film with a circular inclusion that imposes tangential anchoring.