Synthesis And Characterization Of Novel Heterocyclic Liquid Crystal Polymers And Graphene Composites

In this paper,three novel liquid crystal monomers with furan ring as the end group were synthesized and characterized for the first time.At the same time,the polymer and graphene were linked in the form of covalent bond through Diels Alder reaction(DA reaction)using conjugated double bond in furan ring structure.In this paper,the synthesis of new liquid crystal monomers and polymers is reported,and the properties of monomers,polymers and composites are studied by various means.This paper consists of two parts.The first part:three new liquid crystal monomers with furan ring structure were designed and synthesized.Two of them,Mb and Mc,were polymerized with cholesteryl allyloxybenzoate M1 respectively.Two series of side chain liquid crystal polymers were prepared with polymethylhydrosiloxane containing 7 H as the main chain skeleton.The second part:due to the conjugated double bond in the furan ring structure of polymer side chain,it has the ability of DA reaction with reduced graphene oxide(RGO),and bond with the surface and edge of graphene in the form of six membered ring to prepare polymer graphene composite.The molecular structure of the new liquid crystal monomer was determined by FT-IR and 1H-NMR,and the thermodynamic information such as melting point,glass transition temperature and clear point were determined by DSC.The texture characteristics of liquid crystal monomer and polymer were observed by polarized light microscope(POM),and the phase type was determined.The molecular layer spacing was calculated by the diffraction peak obtained by XRD,the phase state of liquid crystal polymer and the structure information of graphene were further determined.The degree of preparation of graphene oxide(GO)and RGO was characterized by Raman spectroscopy,and the DA reaction was confirmed.The thermal decomposition temperature of polymer and composite materials was determined by TGA to analyze the thermal stability of each material.The experimental results show that the structures of the three new liquid crystal monomers are in accordance with the molecular design,and the three monomers have a wide range of liquid crystal phases and high purity.Under POM,three kinds of monomers and two series of polymers show colorful liquid crystal textures,in which the monomers Mb and Md are nematic liquid crystal,Mc is sematic liquid crystal,and the polymers are sematic liquid crystal.The characterization of graphene related materials is mainly based on the Raman spectrum.Through the relative strength of D peak and G peak,we can understand the hybridization of carbon atoms in graphene and prepare for the raw materials of DA reaction.Combined with the results of Raman spectrum and WAXD test,the results show that:GO and RGO are successfully prepared,and the reaction between the polymer and graphene DA is confirmed.TGA test results show that the thermal decomposition temperature of polymer and composite is higher than 320℃,which has good thermal stability,and the thermal decomposition temperature of composite increases with the increase of graphene content in the system.