Synthesis And Properties Of Chiral Liquid Crystal Based On Menthol

Chiral liquid crystals have attracted more and more attention at present. Molecular chirality has a particularly remarkable influence on the macroscopic physical properties of liquid crystal systems. Many physical properties of liquid crystals depend on chir-ality, e.g., certain linear and nonlinear optical properties, the occurrence of ferro-, ferri-, antiferro-and piezo-electric behavior, the electroclinic effect, and even the appearance of new phases. In addition, the majority of optical applications of liquid crystals is due to chiral structures, namely the ther-mochromic effect of cholesteric liquid crystals, the rotation of the plane of polarization in twisted nematic liquid crystal displays, and the ferroelectric and antiferroelectric switching of smectic liquid crystals. In this thesis, we synthesized a series of chiral liquid crystal monomers and side chain liquid crystalline polymers containing menthyl, and their structures and liquid crystal behaviors were identified.This thesis is divided into three parts. In the first part, we synthesized a series of chiral liquid crystal monomers,4-((4-(ethoxy)benzoyl)oxy)phenyl 4-((n-(menthyloxy)-n-oxoacyl) oxy)benzoate (BOP2MBn:BOP2MB1, BOP2MB2, BOP2MB3, BOP2MB4, BOP2MB5, BOP2MB6, BOP2MB10), using menthyl group as chiral primitives,-/-ArCOOArOOCAr-/-as the rigid mesogenic core, ethoxy group as the terminal group. The effect of the length of dicarboxylic acid spacer on liquid crystal properties was discussed. During the heating process, liquid crystal monomers, BOP2MB1, BOP2MB2, BOP2MB3, BOP2MB4, BOP2MB5 present oily streak texture with selective reflection, the monomer BOP2MB6 reveals fingerprint texture, and the monomer BOP2MB10 shows schlieren texture. During the cooling process, monomer BOP2MB1, BOP2MB2, BOP2MB3 show focal conic texture, the monomer BOP2MB4 reveals blue phase and focal conic texture, BOP2MB5 and BOP2MB10 show fingerprint and schlieren texture respectively.In the second part, we synthesized a series of chiral liquid crystal monomers,4-((4-(alkoxy)benzoyl)oxy)phenyl 4-((4-(menthyloxy)-4-oxoacyl) oxy)benzoate (BOPmMB4: BOP1MB4, BOP2MB4, BOP3MB4, BOP4MB4, BOP5MB4, BOP6MB4, BOP7MB4, BOP8MB4, BOP9MB4, BOP10MB4), using menthyl group as chiral primitives,-/-ArCOOArOOCAr-/-as the rigid mesogenic core, alkoxyl group as the terminal group. The effect of the length of alkoxyl group on liquid crystal properties was discussed. This series of liquid crystal monomers present oily streak texture with selective reflection during the heating process, show blue phase and focal conic texture during the cooling process. The length of alkoxyl group on the terminal only make Tm and Ti of liquid crystals shift, and has no effect on the liquid crystal phase.In the third part, we synthesized a series of chiral liquid crystal monomers (M1, M2, M3, M4, Ms, M6) using menthyl group as chiral primitives, a reactive alkene group as end group. A series of Pi-P6 polymers were prepared by graft polymerization using PMHS as backbone.The liquid crystal monomers Mi, M2, M3 present oily streak texture during heating process, reveal blue phase and focal conic texture during the cooling process. M4 presents oily streak texture during the heating process, and reveals blue phase, focal conic texture and SmC* batonnets during the cooling process. M5, M6 present oily streak texture during the heating process, and exhibit blue phase, focal conic texture and twist grain boundary A (TGBA*) during the cooling process. P1?P6 show that this series of polymers present grandjean texture in the liquid crystal range. All liquid crystal monomers and polymers are thermotropic enantiotropic liquid crystal. Chiral nematic liquid crystal of P1?P6 polymers are identified by POM and XRD.