| 摘要: | 本論文的研究主要分成三個部份，探討電致變色材料雙十二烷基二甲基溴化銨(DDAB)與向列型液晶結合後所形成之電致變色系統，旨在優化其變色性能、反應時間與操作穩定性，以提升未來應用於智慧光學元件之可行性。第一部份以單一成分之向列型液晶5CB摻雜DDAB為研究對象，探討液晶盒厚度與DDAB濃度對電致變色行為的影響。結果顯示，當液晶盒厚度為20 μm、DDAB濃度為25 wt%時，樣品展現最顯著的顏色變化與穿透率下降，且具有良好的變色可逆性。透過偏光顯微鏡與光譜儀分析，適當的液晶盒厚度與DDAB濃度有助於變色均勻性與樣品穩定性。第二部分著重於反應時間之優化，考量實際應用對快速切換的需求，設計多種電壓驅動模式進行比較，包括摻雜離子SDS’、脈衝電壓調控以及Pulse-DC-Reverse (PDR)驅動等方式。結果顯示摻雜離子SDS’不僅無法有效縮短反應時間，反而因離子干擾導致著色時間延長。而施加脈衝電壓則能降低離子累積並提升氧化還原效率。進一步在工作週期(duty cycle)為70%、脈衝電壓為20 V的三段式操作條件下，樣品的總反應時間可縮短至約15秒，且顏色變化穩定，樣品不易損壞，為本研究中兼具變色效率與樣品穩定性的最佳操作參數。第三部分探討液晶材料類型對電致變色行為之影響，實驗選用混合型向列型液晶E7摻雜DDAB，並與5CB之變色效果進行比較。由於E7具有較高的相變溫度，樣品在室溫下易出現液晶排列不均所造成的霧化，並導致變色不可逆。雖可透過加熱改善此問題，但不利於實際應用。因此進一步摻雜手性分子(R5011與S5011)以降低液晶混合物的相變溫度，使液晶分子在室溫下可穩定處於各向同性相。結果顯示液晶E7摻雜DDAB結合手性分子後之樣品透明度明顯改善，且變色反應具良好的可逆性與均勻性。;The research topics in this thesis include three main parts, focusing on the development of an electrochromic system formed by combining electrochromic material didodecyldimethylammonium bromide (DDAB) with nematic liquid crystals. The aim is to optimize its color-changing performance, response time, and operational stability to enhance its potential for future applications in smart optical devices. In the first part, the system composed of a single-component nematic liquid crystal (5CB) doped with DDAB is investigated. The effects of cell thickness and DDAB concentration on the electrochromic behavior are studied. The results show that when the liquid crystal cell thickness is 20 μm and the DDAB concentration is 25 wt%, the sample exhibits the most pronounced color change and transmittance reduction, along with good reversibility. Analysis via polarized optical microscopy and spectrometer indicates that appropriate cell thickness and DDAB concentration contribute to improved color uniformity and sample stability. The second part focuses on optimizing the response time, considering the practical demands for rapid switching. Various voltage driving schemes are designed and compared, including doping with ionic surfactant SDS’, pulsed voltage control, and Pulse-DC-Reverse (PDR) driving. The results reveal that doping with SDS’ not only fails to shorten the response time but also prolongs the coloration time due to ionic disturbances. In contrast, applying pulsed voltage can reduce ion accumulation and enhance redox efficiency. Under a three-stage operation condition with a duty cycle of 70% and a pulsed voltage of 20 V, the total response time of the sample can be reduced to approximately 15 seconds, with stable color change and minimal sample degradation. This represents the optimal operating condition balancing coloration efficiency and sample durability in this study. The third part investigates the influence of different liquid crystal materials on electrochromic performance. A mixed-type nematic liquid crystal (E7) doped with DDAB is compared with 5CB in terms of color-changing behavior. Due to the higher phase transition temperature of E7, samples tend to exhibit haze at room temperature caused by non-uniform liquid crystal alignment, resulting in irreversible color changes. Although this issue can be mitigated by heating, such a requirement is unfavorable for practical applications. Therefore, chiral dopants (R5011 and S5011) are introduced to lower the phase transition temperature of the liquid crystal mixture, enabling a stable isotropic phase at room temperature. The results show that samples composed of E7 doped with DDAB and chiral additives exhibit significantly improved transparency, with reversible and uniform electrochromic responses. |
