Synthesis And Characterization Of Self-healing Shape Memory Liquid Crystal Elastomer Based On Rigid Main Chain

In this dissertation we reported the preparation of a series of self-healing liquid crystalline elastomers(LCEs) with different hydrogen content. This paper focused on the phase behavior, thermo-responsive, rheological behavior, as well as the self-healing properties of LCEs. The content mainly includes following several aspects.1. Random copolymer Px(PHCS-co- PHUUx, x=0, 1, 2, 3, 4,) were successfully synthesized using the designed monomer 2-[6-(6- methyl- 4- pyrimidine ketone)-urea- hexamethylene carbamate] ethyl acrylate(HUU) and di(hexyl) vinylterephthalates(HCS) via free radical polymerization. Previous research results showed that the steric effect of side group made the main chain of PHCS extended, so that the polymer chains were columnar. The column of polymer chain can be arranged in parallel form a long range ordered columnar liquid crystal phase. A novel cross-linked siloxane-based polymer network P’x(PMHS-g-(PHCS-co-PHUUx), x=0, 1, 2, 3, 4) has been synthesized by the hydrosilylation of polymethylhydrosiloxane(PMHS) partly substituted with HUU and HCS. The crosslinker HUU containing multiple hydrogen bonds and HCS acted as liquid crystalline portion. GPC and 1H NMR are employed to confirm the structure of LCEs.2. The phase transition of these LCEs in detail as well as their LC ordered structure were investigated by one-dimensional wide-angle X-ray diffraction(1D WAXD). The results showed that the increasing of PHUU could promote the development of liquid crystal phase, but the polymer showed the amorphous state while the content of HUU reaches fifteen percent. The ordered phase structure was destroyed. At the same time, the relation between the content of hydrogen with thermo-responsive, self-healing behavior and rheological properties of polymers were also investigated. The results showed the LCEs could self-heal well even in room temperature. In addition, variable temperature infrared results show that the displacement of hydrogen bonding changes with the temperature.3. The phase transition and LC structure for LCEs(P’x) that based on polysiloxane backbones have been carried out by X-ray experiments. Variable temperature 1D WAXD results revealed that the polymer P’x with different hydrogen bonds content that the diffraction peak intensity in the low angle does not change with the change of temperature. Self-healing test results show that polymer could selfheal well even in room temperature. The thermo-responsive of these LCEs is reversible.