Abstract
本研究經仔細的分子設計合成十二系列含芳香苯酯液晶基的單體及其側鏈液晶聚合物。結構包括以寡氧乙烯基為間距，其單位(n)為0- 3；液晶基為苯酸苯酯、苯酸聯苯酯、聯苯酸苯酯、聯苯酸酯、聯苯酸聯苯酯；末端旋光基為含1-3 個旋光中心以及4-7個碳原子長的烷基鏈高分子主鏈為聚矽氧烷；高分子共聚合物主鏈為聚二甲基矽氧烷。研究分為三大部份：第一部份為強誘電性液晶單體的合成、液晶相熱行為與光電性質之探討。合成十二系列如前述結構之組合的強誘電性液晶單體。液晶相熱行為經由熱微差掃瞄卡計、偏光顯微鏡以及粉末 X-ray 繞射加以鑑定液晶相的種類與排列結構，並以分子模擬的理論來證明實驗之正確性；探討不同液晶基、間距以及末端旋光基對液晶相行為之影響。而液晶相的光電性質則經由自發極化值、應答時間、傾斜角與介電性質的分析，建立光電測試的技術與設備，並對自發極化值與分子結構作一詳細的討論。結果顯示，在三苯環與四碳烷基鏈長的系統，且較剛硬的聯苯基團靠近末端旋光基，可呈現約 90 ℃且包含室溫的 Sc* 相範圍；而由於強大的偶極與均一的排列，其自發極化值可達約 400 (nC/cm2) ，速度可達約 10ms。而四苯環的液晶基系統，可呈現 200 ℃的溫度相範圍 (其中包括約 100℃以上的 Sc*相)。第二部份為強誘電性側鏈液晶均聚合物之合成與鑑定。將第一部份所合成之十二系列的單體進行與聚矽氧烷之矽氫化接枝反應，可得十二系列強誘電性側鏈液晶均聚合物。其液晶相的鑑定與分析亦以熱微差掃瞄卡計、偏光顯微鏡以及粉末 X-ray 繞射來分析液晶相的種類與液晶分子在聚合物中的排列結構。並討論高分子主鏈對液晶相行為的影響。結果顯示，高分子聚矽氧烷主鏈的導入，不僅擴展了整體液晶相的溫度範圍，並也擴展了 Sc* 相可達約 190℃的範圍。第三部份為強誘電性側鏈液晶共聚合物之合成、鑑定與光電性質探討。選擇具有較大自發極化值的單體進行不同接枝量的聚矽氧烷共聚合物反應。並探討高分子共聚合主鏈對液晶行為的效應。研究結果顯示，降低了液晶含量的比例，可使 Sc* 相範圍往低溫平移，甚至包含室溫的範圍，此現象在三苯環系統中有不錯的效果；四苯環系統由於結晶性高，熔點明顯的出現但不隨接枝量的比例降低而下降，因此對於平移 Sc* 相範圍無太大之功效。粉末 X-ray 繞射測試與分子模擬的分析顯示強誘電性側鏈液晶共聚合物具有微相分離的結構。力。The goal of this research is to develop the ferroelectricliquid crystal and ferroelectric liquid crystalline polymerswhich can exhibit wide chiral smectic C phase range (includingroom temperature), and excellent electro-optical properties.These FLC/FLCPs' structures contain the flexible spacer chain,mesogenic group, chiral moiety and polymeric backbone. Severaldifferent chiral moieties with 1-3 asymmetric centers on thebutyl or heptyl alkyl chains are used. The polymeric backbonesare polymethylhydrosiloxane or copolydimethylsiloxane. Theelectro-optical properties (for example the spontaneouspolarization, response time, tilt angle, and dielectricanalysis) of FLC/FLCPs were also examined. Results obtainedhere show that the most suitable liquid crystalline structuresfor the formation of chiral smectic C phase are those whichconsist of oligo(oxyethylene) spacer, chiral butyl chain lengthcoupling with three to four phenyl rings of ester mesogeniccores. The Sc* phase range can be achieved about 90.The highspontaneous polarization value and quite fast response time arefound in some FLC system with two asymmetric centers on thechiral moiety. Finally, the copolysiloxane as the polymericbackbone is quite helpful for lowering the viscosity and shiftthe Sc* phase range to room temperature of ferroelectric sidechain liquid crystalline polymer system. That is due to themicrophase separation of side chain liquid crystallinecopolysiloxane. The spontaneous polarization value (~200nC/cm2)and less 1ms response time were also achieved. These materialsexhibiting the broad temperature range of Sc* phase andexcellent electro- optical properties simultaneously are highlypotential for the E-O applications.