Synthesis and Studies of Covalent- and Hydrogen-Bonded Blue Phase Liquid Crystals and its Polymers Containing Bi-mesogenic Cores

• Main Authors: Wei, Chong-Lun, 魏崇倫
• Other Authors: Lin, Hong-Cheu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/60630125151405749867

博士 === 國立交通大學 === 材料科學與工程學系所 === 103 === 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.