觀察藍相液晶於電場作用下之長晶

Abstract

研究藍相液晶之晶體長晶機制與控制晶體長晶一直是相當重要的課題。在本論文中我們由觀察藍相液晶於電場作用下之結構變化出發，並且可控制藍相液晶晶體尺寸與使之具均勻轉向。根據觀察結果，我們並提出電場循環下之長晶機制。藍相液晶於外加電壓下，各轉向之藍相液晶解旋相轉成膽固醇液晶相。當電壓關閉後，因藍相液晶之[220]轉向之晶體可滿足邊界之最小自由能而快速成核，使得晶體尺寸增加，同時此[220]轉向之晶體也抑制了其他晶體轉向之生長。隨著電壓的循環次數增加，[220]晶體尺寸逐漸擴大，並具有晶體轉向一致之效果。此研究也為藍相液晶在光子元件設計開啟了新的一扇窗。

The mechanism of the crystal growth of blue phase liquid crystals (BPLCs) and how to control the crystal growth are important. In this thesis, we start from the observation of the transition of the morphologies of BPLCs under an applied electric field and then we are able to control the domain size and the uniformity of BPLCs. We also propose the mechanism of the crystal growth of BPLCs under an applied electric field. When the voltage is on, the structure of BPLCs transits the blue phase to the cholesteric phase. Then when the voltage is off, the crystal plane of [220] satisfying minimum surface free energy grows rapidly and then the domain size enlarges. Meanwhile, the other orientations of BPLCs are suppressed. As the voltage is on and off several times, the domain size and the uniformity of the crystal plane of [220] are increased. This study opens a new window for BPLC-based photonic devices.