Study On The Structure And Properties Of Thermotropic Liquid Crystalline Polyurethane Elastomers And Its Polystyrene Composite

In this thesis, the research and development of liquid crystalline polyurethaneelastomer (LCPUE) and molecular composite were reviewed. Synthesis, properties andinfluences of LCPUE were concluded, then the wide applying prospect of LCPUE inpreparing composite materials was included. The synthesis of LCPUE:Ⅰ. The butyl1,4-bis(p-hydroxybenzoates) (BHBB) was prepared from 1, 4-butanediol and methylp-hydroxybenzoate, then polyurethane elastomer was synthesized from BHBB andTDI-100.Ⅱ. BMPT was synthesized from methyl p-hydroxybenzoate and p-Phthaloylchloride in 1,1,2,2-tetrachloroethane, then TOBB was prepared from BMPT and1, 4-butanediol with butyl titanate as the catalyzator, the PUE was synthesized fromTOBB and TDI-100. The polymers were characterized by fourrier transform infrared(FT-IR). The molecular weights of the polymers were determined by gel permeationchromatography (GPC). The LC nature and of the PU was confirmed by differentialscanning calorimetry (DSC). Polarizing optical microscope (POM) was used toobserve the structure of the mesophases. The composite of PS and LCPUE wasextruded and injected. The mechanical properties of the composite materials weretested, as well as the thermal properties and microstructure were viewed by DSC,POM and SEM. The PUEs synthesized showed thermotropic liquid crystalline natureat the temperature between melting-point(Tin) and cleaning-point(Ti). The averagemolecular mass of the PUE synthesized were up to 20,000, and the distribution is closeto 1. Otherwise, with the increasing of the number of methylene (from 4 to 6), theenthalpy of the thermal transition(Tin) of the LCPUE will be high, while the there is little influence on the enthalpy of the thermal transition(Ti). With the increasing ofrigidity the Tm and Ti were increased to 188.1℃and 263.3℃respectively, and thetemperature range of the liquid crystalline is widen. The mechanical properties of thecomposite materials have been improved; hardness was improved by 1.5 times. TheLCPUE fiber structure of the composite materials was observed by scanning electronmicroscope (SEM), and the KH-550 improved the compatibility of the LCPUE and PS.The diameter of the fibers is uniform, which is 300nm.