氫鍵及共價鍵雙桿狀藍相液晶及其高分子材料之合成與研究

Abstract

藍相液晶具有獨特的光電特性及其特殊紋理，許多專家對於藍相液晶的研究十分看好，藉由新材料的開發與合成，藍相液晶相當有潛力成為下一代液晶顯示器的前瞻材料。 在 Chapter 2 中，探討了新穎性雙節棍型分子結構 (bi-mesogenic core) 以製備藍相液晶 (blue phase liquid crystal) 材料之研究，並引進不同對掌中心 (chiral center) 位置及個數用以產生新穎自組裝之藍相液晶與特殊光電材料性質，並研究對掌中心的位置及個數對藍相液晶溫寬的影響。 Chapter 3 中，首次將壓克力基引進雙節棍型分子結構中製備出第一個藍相液晶單體 (blue phase monomer) 材料，並以此藍相液晶單體聚合後得到藍相液晶共聚高分子，研究不同的共聚比例對於高分子藍相液晶溫寬的拓展趨勢。 Chapter 4 裡，探討將氫鍵引進雙節棍型分子結構中以產生新穎自組裝之氫鍵藍相液晶，並首次以此氫鍵藍相液晶與前述共價藍相液晶材料性質做比較，藉由理論模擬計算來了解液晶分子的雙軸性 (biaxiality), 彎曲角 (bent angle) 及 偶極矩(dipole moment) 對於藍相液晶溫寬的穩定影響。

Two series of novel asymmetrical single- and double-chiral liquid crystal diads using a central linker to link two different mesogenic cores were successfully synthesized. The effects of the position of chiral centers and the number of aromatic rings on the mesomorphic and electro-optical properties were investigated. According to our experimental results and molecular modeling, the mesomorphic properties and temperature ranges of BPs will be affected by the values of biaxiality and dipole moment, along with the bent shape of molecular geometry. Therefore, we demonstrated the first example of asymmetrical single- and double-chiral liquid crystal diads involved chiral centers located at the central linker to exhibit BPs, including the mesophases of BPI and BPIII, which might offer new BP single-components to the future applications of eutectic liquid crystal mixtures with wide BP ranges. Novel blue phase (BP) reactive monomers M1 and M2 containing a bi-mesogenic core are first reported by introducing two end-attached acrylic spacers with different lengths. Due to the self-assembly of bi-mesogenic cores with the same side-by-side end-attached acrylate spacers in homopolymers P1 and P2, no blue phase could be induced by homopolymerization of M1 and M2. However, by interrupting the self-assembly of bi-mesogenic cores with different side-by-side spacer lengths of copolymers P12, double-twisted cylinders of BPIII could be further extended by copolymerization of M1 and M2 with different molar ratios. With M1:M2 = 5 : 5 (molar ratio) in both side-chain copolymers P12(soln:5/5) and P12(photo:5/5) rather than binary mixture M1/M2(5/5), the widest BPIII ranges of 5.3 °C and 3.8 °C could be obtained by solution- and photo-polymerization, respectively. A series of novel asymmetric hydrogen-bonded (H-bonded) dimeric complexes D/P and D/P* (proton donors D = A, A*, AF and AF*) were synthesized and self-assembled by appropriate molar ratios of H-donors (A, A*, AF and AF*) and H-acceptors (P and P*). In addition, the influences of the lateral fluoro-substituent of H-donors, the number (along with the position) of chiral centers and the molar ratio of H-donors and H-acceptors on the mesophasic behaviours (e.g., BPs) of asymmetric H-bonded dimeric complexes are investigated.