Synthesis And Properties Of Multi-arm Schiff Base Liquid Crystal Polymers

Due to the liquid crystal(LC)chemistry continuous development,the exploration of new LCs has aroused people attention.The research of LC compounds and LC polymers has become the focus of professional attention.The multi-arm LC compound is a novel LC material which connects multiple LC arms to a central atom or group.The Schiff base LC compound has excellent LC properties and is widely used.The novel LC compound with cholic acid as the central molecule breaks through the limitation of the conventional rod-like LC compound,and the novel LC polymer exhibits excellent LC properties.Based on the related literatures,this paper has synthesized three kinds of Schiff base LC arms and combined them with cholic acid to prepare three-arm Schiff base LC macromolecules through esterification reaction.Then the Schiff base LC polymer with flexible polysiloxane backbone and cyclic polysiloxane backbone has been synthesized.The experimental content in this dissertation is divided into the following two parts:The first part has synthesized Schiff base monophenols 4-p-methoxybenzifloxacin phenol(AS1),4-p-methylphenyl Schiff base phenol(AS2),4-p-chlorophenyl siver Alkali phenol(AS3),then with adipic acid through esterification reaction synthesized liquid crystal arm 4-p-methoxybenzifloxacin phenoxycarbonyl valeric acid(BS1),4-p-methylphenyl Schiff base phenoxycarbonyl Valeric acid(BS2),4-p-chlorophenyl Schiff base phenoxycarbonyl valeric acid(BS3),and finally connected to the center of cholic acid to prepare three-arm liquid crystal compounds with different terminal groups:tris(4-p-methoxyl)Benzifloxacin oxyformylvaleric acid)cholate(CS1),tris(4-p-methylphenylhsinyloxycarbonyl valerate)cholate(CS2),tris(4-pchlorophenylhiver Alkaline oxyformylvalerate)cholate(CS3).The results of FT-IR and 1H-NMR showed that the structure conformed to the molecular design.The result of DSC,POM and XRD showed that CS1-CS3 have liquid crystallinity.CS1 is thermotropic enantiotropic nematic LC which exhibits textured texture.The LC interval during heating is 59.6?,and during cooling is 69.6?.CS2 is thermotropic enantiotropic nematic LC which exhibits textured texture.The LC interval during heating is 57.3? and during cooling is 64.4?.CS3 is thermotropic enantiotropic nematic LC which exhibits textured texture.The LC interval during heating is 65.3?and during cooling is 80.9?.LC interval:CS3>CS1>CS2.The second part has synthesized 4-hydroxyphenyl 4-(allyloxy)benzoate(E),and combined with 1,1,1,3,5,5,5-heptamethyltrisiloxane(PMHS)and 2,4,6,8-tetramethyl-1,3,5,7,2,4,6,8-tetraoxatetrasilocane.A series of polymer precursors PQL(PQL-1,PQL-3,PQL-5,PQL-7),PQH(PQH-1,PQH-2,PQH-3,PQH-4)have been synthesized by side chain copolymerization.The PQL series intermediates were esterified with CS,,CS2 and CS3 in different proportions to synthesize a series of LC polymers PL1(PL1-1-PL1-7),PL2(PL2-1-PL2-7),PL3(PL3-1-PL3-7),the PQH series precursors were esterified with BS1 and CS1 in different proportions to synthesize a series of polymers PH 1(PH 1-1-PH1-4)and PH2(PH2-1-PH2-4).The FT-IR analysis showed that the structure conformed to the molecular design.The results of DSC and POM showed that the PL1,PL2,and PL3 series of polymers are all thermotropic enantiotropic nematic LCs.The LC phase interval in heating are 9.2-70.1?,27.7-59.0?,67.8-77.1?respectively,and the LC phase interval in cooling are 12.2-91.4?,46.1-66.4?,33.1-91.5? respectively.The melting points and clearing spots show decreasing firstly and then rising with the increase of the number of branches.The melting point and clearing point of the polymer with 3 branches is the lowest.The PH1 and PH2 series polymers do not have liquid crystallinity,and the melting points range are 146.85-172.78? and 158.14-170.48? respectively;the melting points of PH1 series increasing with the increase number of branches,and the melting points of PH2 series show decreasing firstly and then rising with the increase of the number of branches.UV absorption red shift:PL3-7>PL1-7>PL2-7,and the absorbance increase as the content of the mesogen units increases.