Study On Optical Properties Of Some Cholesteric Liquid-Crystalline Polymers

In recent years, chiral side-chain liquid crystalline polymers (LCPs) have attracted considerable attention and interest, mainly because of their unique properties, including the selective reflection of light, potical rotation, circular dichroism and ferroelectricity, and their petential applications in numerous areas, especially in the fields of optics, thermoconduction materials, and fast switching.In this paper, one serie of cholesteric liquid crystalline polymers and their purified products by ethanol were chiefly studied. These polymers were synthesized by graft polymerization with two cholesteric liquid crystalline monomers (M1,M2) and one nematic liquid crystalline monomer (M3) using methylhdrosiloxane as backbone. Properties of monomers and polymers, including texture, optical were investigated by polarizing optical microscopy(POM), polarimeter, UV/Vis/NIR spectrophotometer, FT-IR spectroscopy and FT-IR imaging system. Moreover, phase trasitions of liquid crystals were investigated by differential scanning calorimetry(DSC). generic solution measure was not applied when progressing with polarimeter and UV/Vis/NIR spectrophotometer. But solid samples would be directly testing after being prepared to be a film, and this is an innovation in this paper. Especially, FT-IR imaging system is applied for studying properties of cholesteric liquid crystal, which is not seen in any report all over the world, so it will be a new exploration.In addition, compared the results of polarizing optical micropolarscope, polarimetric and selective reflection analysis to the results of the differetial scanning calorimetry (DSC), we found these different datas are interrelated in a certain extent, in particular when phase transition occurred. So the optical rotation and the selective reflection of cholesteric liquid crystals at different temperature relate to the heat motion of moculars.Timingly testing any IR change of cholesteric liquid crystalline monomers and polymers could be put in to effect by FT-IR image system at every temperature. Combined with two-dimensional correlation analysis, the datas offered by FT-IR image system could be discribed the compatibility and the difference of IR absorbence intensity. As a new way to characterize the cholesteric liquid crystal, I believe that FT-IR imaging system will be more valuable and potential in use.