Preparation Of Chiral Liquid Crystal Compounds And Polymers Based On Menthol

Chiral liquid crystals refer to compounds that contain chiral carbon atoms(C*)in molecular structure,these materials not only have the liquid crystalline properties,but also have many excellent optical performances due to the presence of chiral center,and have great potential for application in the aspects of optical devices and display.For example,the majority of optical applications of liquid crystals are due to chiral structures,namely the thermochromic 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 compounds and side chain liquid crystalline polymers containing menthyl,their structures are in accordance with the molecular design.This thesis is divided into three parts.In the first part,we synthesized a series of chiral liquid crystal compounds MnB4B(n=4,5,6,7,8,9,10),using menthyl group as chiral primitives,-/-ArCOOAr-Ar-/-as the rigid mesogenic core,butoxy group as the terminal group.The effect of the length of dicarboxylic acid spacer on liquid crystal properties was discussed.During the heating process,the compounds MnB4B(n=4,5,6)presented a phase transition sequence as Cr-N*-Iso,the compounds M7B4B and M10B4B showed phase process as Cr-SC*-N*-Iso.And a phase transition sequence of compounds M8B4B and M9B4B is Cr-SX*-SC*-N*-Iso.During the cooling process the compound of M4B4B revealed Iso-N*-Cr transition process;Iso-N*-SC*-Cr phase transition for compounds M5B4B;and Iso-N*-SC*-Sx*-Cr process for compounds M6B4B,M7B4B,M8B4B,M10B4B.For liquid crystal compounds MnB4B series,a pronounced odd-even effect on the clearing temperature is observed when the parity of the pacer chain is varied.Compounds with an odd number of spacer length have higher clearing transition temperature than even number which show liquid crystal compounds with an odd spacer length have better order.In the second part,we synthesized a series of chiral liquid crystal compounds MOBnB(n=2,4,6,8,10,12,14,16,18),using menthyl group as chiral primitives,-/-ArCOOAr-Ar-/as the rigid mesogenic core,adipic acid acting as space group,alkoxy group as the terminal group.The effect of the length of alkoxy group on liquid crystal properties was discussed.The results show that during the heating process MOBnB(n=2-4)presented a phase transition sequence as Cr-N*-Iso,the compounds MOBnB(n=6-14)showed phase process as Cr-SC*-N*-Iso.And a phase transition sequence of compounds MOB16B and MOB18B is Cr-SC*-Iso.During the cooling process the compounds of MOBnB(n=2,4,6)revealed Iso-N*-SC*-SX*-Cr transition process;and Iso-N*-SC*-SX*-Cr process for compounds MOBnB(n=8-18).In addition,with the increase of the number of terminal alkoxy groups N*phase narrows,however,SC*phase widens.This shows increase of the number of terminal alkoxy groups favors formation of smectic phase.In the third part,we synthesized a series of chiral liquid crystal monomers MnBAB(n=4,6,8,10),using menthyl group as chiral primitives,a reactive alkene group as end group.A series of P1～P4 polymers were prepared by graft polymerization using silicone oil as backbone.During the heating process,M4BAB presented a phase transition sequence as Cr-N*-Iso;the monomer M6BAB showed phase process as Cr-SC*-N*-Iso;the monomer M8BAB phase process as Cr-SX*-SC*-N*-Iso.And a phase transition sequence of monomer M10BAB is Cr-SX*-SC*-Iso.During the cooling process the monomer of M4BAB revealed Iso-N*-SC*-Cr transition process;and Iso-N*-SC*-SX*-Cr process for monomers MnBAB(n=6,8,10).A series of P1～P4 polymers were prepared by graft polymerization using PMHS as backbone.P1～P4 show that this series of polymers present iridescent texture in the liquid crystal range.Polymers P1～P4 are identified as smectic A liquid crystal.