The Synthesis And Characterization Of Liquid Crystal Polyrotaxane By Virtue Of The Mobility Of Threaded α-cyclodextrins

Cyclodextrins(CDs) can selectively form pseudopolyrotaxane with polymer chains by non-covalently mechanical interlock interaction. In order to promote the stability of this system, bulky groups are usually used to end-cap the pseudopolyrotaxane to prepared so called polyrotaxane(PR). Due to the unique mobility of CDs, PR has enormous potential applications in the field of stimuli-responsive materials, intelligent materials, biomedical materials and liquid crystal materials and so on. There were some pioneer researches regarding the preparation of liquid crstal polyrotaxane. However, these researches still utilized traditional strategy for liquid crystal polymer(LCP) preparation that long and flexible spacer between main chain and mesogens was introduvced in order to suppress "matrix effects". In this paper, PR with high yield were firstly synthesized by in situ Michael addition reaction, then azobenzene mosegens were directly endowed into PR by the esterfication of 4- phenylazo benzoyl chloride and CD’s hydroxyl to prepare azobenzen substituted PR(AzoPR). Furthermore, it was found both PR and AzoPR as novel spacerfree LCP can exhibite liquid crystal phase by virtue of the mobility of threaded CDs. The detailed research results are as follows:Firstly, the vinyl-PEG(v-PEG) and α-CD were self-assembled into pseudopolyrotaxane(PPR) in water, then PPR was in situ terminated by SH-β-CD to synthesize PR with high yield. The influences of the feeding amount, as well as the solvent composition on the yield and the number of threaded CDs were thoroughly investigated. Furthermore, the azo mesogens were introduced PR without any spacer by the esterfication of 4- phenylazo benzoyl chloride and CD’s hydroxyl.Secondly, It was found AzoPR can form thermotropic liquid crystal phase at 180 ℃, and the XRD results showed it exhibited nematic liquid crystal phase. On the other hand, AzoPR also can form lyotropic liquid crystal in DMSO. The thermotropic liquid crystal phase mainly results from coordination of azo mosogen’s π-π stack and the movement of threaded CDs, while its lyotropic liquid crystal phase is ascribed to the movement of CDs.Finally, since the threaded CDs in PR possessed same movement in DMSO with those in AzoPR, PR’s lyotropic liquid crystal phase was also found in DMSO. The liquid crystal structure was observed by TEM, whereas the XRD results showed it exhibited typical hexagonal crystal system.