| The molecular arrangement of cholesteric liquid crystal has acertain direction,is not as stable as crystal structure,but is easily influenced by electric,magnetic,temperature,stress and impurities.The different arrangement can lead to many optical changes of the liquid crystal.The kind of array endows the cholesteric liquid crystal with a unique mobility,dielectric and optical properties,and the optoelectronics of the cholesteric liquid crystal has gained wide researchers’ attention.Graphene oxide has good optical,mechanical,thermal properties,which is expected to be used in nano-devices and high-performance batteries and so on.Oxygen groups on graphene oxide’s surface are rich and easily interacted with other active molecular structures.First,the 10-cholesteroxy-10-oxocaproic acid(COOA)was chosen as the filler to fabricate the composite film.The COOA/PAA composite films were prepared by in-situ polymerization method.The structure,composition,fabrication temperature was analyzed by SEM,FTIR and Raman.And the dispersion of liquid crystal molecules in PAA matrix and its effect on the dielectric properties were also investigated.The results showed that the pure liquid crystal phase of COOA appeared between 101 ℃ and 132 ℃,but the texture of liquid crystal in the matrix appeared at 145 ℃.It means that the interaction between COOA and PAA improved the liquid crystal transition temperature.When the temperature was at 145 ℃,the composite film had obvious fluorescence at 420 nm and 580 nm.Polar group –COOH of COOA can improve the dielectric properties of PAA matrix.When the doping amount of COOA was 1wt%,the dielectric constant reached to 12,and the electrical loss was only 0.11.GO,COOA co-doped PAA composite films were prepared by in-situ polymerization.The effects of different ratios of graphene oxide and COOA,preparation temperature were studied.The results indicated that GO can interact with COOA via hydrogen bond on the surface of GO.GO could be reduced to RGO at higher temperature.As the temperature increased,the Tg of the composite film decreased with the increase of film fabrication temperature.When the film was fabricated at 145 ℃,the fluorescence of the composite film showed red shifted obviously compared with COOA/PAA composite film.When the doping ratio of GO and COOA is 1: 1,the composite film exhibited good dielectric properties of ~ 147.The RGO-PEI-COOA/PAA composite films were prepared by in-situ polymerization,and the effects of different content of RGO-PEI-COOA on dielectric properties were studied.It indicated that the composite films showed low dielectric loss,but the improvement of dielectric constant was not obvious owing to the packing of macromolecular chain on reduced graphene. |
