Structure Construction And Performance Control Of Liquid Crystal Polyurethane Materials

This thesis introduced the physical and chemical properties and its influencing factors, synthetic methods and applications of liquid crystal polymer (LCP) and liquid crystal polyurethane (LCPU). And then presents the current research advances and research significance of LCPU material.Three architecture systems were designed, a total of 18 kinds of synthetic LCPU materials were studied to discuss the effects of bisphenol A-based mesogenic unit on LCPU properties and phase transition temperature; flexible spacer length on phase transformation temperature of LCPU with biphenyl; hard segment structure on performance and phase transition temperature of LCPU with biphenyl.System I:bisphenol A, MDI/TDI and diols with different flexible chain lengths (ethylene glycol,1,4-butanediol,1,6-hexanediol, diethylene glycol, dipropylene triethylene glycol) as raw materials, six kinds of polyurethane elastomers were synthesized in the same route. The structure and properties of the products were characterized by FTIR, DSC, POM and other characterization methods. The results showed that only product A-T-E exhibits partially liquid crystal phenomenon with melting point 78 ℃, clearing point 137 ℃, liquid crystal temperature range 59 ℃. It also indicates that the liquid crystal performance of hard segment based on bisphenol A and MDI structure is not strong.System II:three kinds of liquid crystal chain extenders BP2, BP4 and BP6 were synthesized based on biphenol (BP), and then synthesized nine kinds of polyurethane products. Hard segment structure was based on MDI, by changing the species of chlorohydrin (2-chloroethanol,4-chlorobutanol,6-chloro-hexylalcohol) and diols (ethylene glycol,1,4-butanediol,1,6-hexanediol) to adjust the length of the flexible spacer structure of 9 kinds of polyurethanes. Using FTIR,1H-NMR, DSC, POM, TGA, XRD and other analytical tools to characterize the products. The results show that BP2, BP4 and BP6 have significant liquid crystal performance, all can be used as liquid crystal chain extenders. However, the liquid crystal performance of PU products is not obvious.System III:biphenol (BP) is used as substantially mesogenic unit, fixed 6-chloro-hexanol as the chlorohydrin,1,4-butanediol as diols, only changing the type of the diisocyanate (MDI/TDI/IPDI/NDI), four kinds of liquid polyurethane products with different hard segment structure were synthesized in the same routes. The products were characterized by means of FTIR,^-NMR, DSC, POM, TGA, XRD and other analysis methods. The results show significant liquid crystal performance of PU10, as thermotropic nematic liquid crystal polymer, its melting point is 90 ℃, the clearing point 111 ℃, liquid crystal temperature range 21 ℃. It indicates that in the case with the same soft segment, the hard segment structure has a greater impact on the liquid crystal performance of polyurethane. And hard segment based on TDI structure exhibits better liquid crystal performance in this architecture.