Enhancement of Polymer Structural Ordering in Polymer-Stabilised Blue Phases for Improved Electro-Optical Properties

Hirotsugu Kikuchi,Shizuka Anan,Takahiro Ashimine,Hiroki Higuchi,Yasushi Okumura,Zehui Qin

doi:10.3390/sym13050772

Abstract

Polymer-stabilised blue phase (PSBP) could be employed in novel fast response optical and photonic devices. It is inferred that inside PSBPs, the polymers are selectively aggregated by location in −1/2 disclinations, which are defects coexisting with the blue phase as a periodic lattice, thereby extending the temperature range of the blue phase. The polymer aggregate structure in PSBPs strongly affects their physical properties. In this study, we employed a non-destructive synchrotron ultra-small-angle X-ray diffraction analysis to investigate the effect of polymerisation rates on the polymer aggregate structure in PSBPs prepared with monomers of different polymerisation rates and examined the structure formation process of the polymer during polymerisation. When methacrylate monomers, which exhibit a relatively low polymerisation rate, were used to form polymers in PSBP, the resulting polymer was more selectively aggregated at disclinations in the PSBP. Furthermore, the electro-optical effect in the PSBP was successfully improved by reducing the polymer concentration in the PSBPs prepared with the optimised monomer combinations.

Highlights

Introduction and Sadahito UTOIntroducing chiral symmetry into nematic liquid crystals induces twisted molecular arrangements
The aggregation structures of polymers inside polymer-stabilised blue phase (PSBP) were evaluated by synchrotron The aggregation structures of polymers inside PSBPs were evaluated by synchrotron
The PSBPs were prepared with various combinations of acrylate and ultra-small-angle X-ray diffraction (USAXD) analyses

Summary

Introduction

Introducing chiral symmetry into nematic liquid crystals induces twisted molecular arrangements. Double-twisted arrangements, which cannot continuously fill the three-dimensional space, predominate over simple twists. The cholesteric blue phase, hereafter referred to as the blue phase, is a liquid-crystal phase caused by the frustration between double-twisted molecular arrangements and the uniformity of the three-dimensional (3D) space, i.e., defect-free structure of molecular arrangement [1,2,3]. Since the blue phase is a result of the preference of the double-twisted structure over the uniformity of the 3D space, it necessarily coexists with defects, i.e., −1/2 disclinations. The main feature of the blue phase is that it spontaneously forms a three-dimensional periodic lattice, which has been confirmed by real space observation [4], and thereby defects form a three-dimensional periodic lattice. PSBP is optically isotropic when no electric field is applied, and birefringence occurs when an electric field is applied

Objectives

Methods

Findings

Discussion

Conclusion