Photochemistry Behaviors And Memory Effects Of Photosensitive Chinnamoyl Moieties

Cinnamoyl moiety could both be photoisomerized and [2+2] cyclized under UV irradiation. These photoreactions could make changable molecular volume which was independent of heat. Thus, cinnamoyl moieties could be applied widely. Photosensitive polymer chains could be oriented by exposed to the linearly polarized ultraviolet light. Since this was reported, a considerable amount of research has been directed towards photo-induced liquid crystal alignment. Photo-orientation becomes a new investigative hotspot because it is an important part of photo-induced liquid crystal alignment. Conversely, photo-de-orientation mechanism was presented in this study. Photosensitive anisotropy materials were synthesized, exposed by UV light and de-oriented because of either photoreaction, then images of difference phase were prepared. Photochemistry Behaviors of cinnamoyl moiety and memory efects of cinnamoyl moiety and PVA were systematicly studied.Results of experiments demonstrated that the existence of free radical initiator could not initiate photodimerization of cinnamoyl moieties. UV-Vis spectral analysis was used for studying the kinetic behaviors of cinnamoyl moiety photoreaction. The photoreaction kinetics of cinnamoyl moiety in solution fit to first order excellently. Cinnamoyl moiety in solid state only involves photodimerization. Different phases of liquid crystal would influence photoreactions of cinnamoyl moiety in liquid crystal phase hugely. These investigations have enabled us to present new data and interpretations regarding the [2+2] photocycloaddition reaction. What's more, it can also be used to analyze the photoreaction of the C=C bond which is expected to control the reflected band and the color of cholesteric liquid crystals. The investigation was taken as the guidance to study memory effects of cinnamoyl moieties, from both liquid crystal and photosensitive polymer.Cinnamoyl moiety liquid crystal was synthesized and memory effect was studied. Dicholesteryl diphenyl cyclobutanediate was synthesized by photodimerization of cholesteryl cinnamate. Glassy cholesteric liquid crystal was prepared. The test showed it could be used as a rewritable color recording material. The principle of glassy liquid crystal was discussed. In-situ studies of structural and morphological changes during the process forming glassy liquid crystal were carried out using synchrotron wide-angle X-ray diffraction (WAXD) techniques and DSC. It can be concluded from DSC and synchrotron WAXD that the crystallization peak moves from high temperature to low temperature with the increasing cooling rate. If the cooling rate is fast enough, it can make the glass transition temperature higher than the crystallization temperature. Thus, glassy liquid crystal was vitrified instead of becoming into crystal state and the cholesteric color was fixed.Photo-de-orientation and memory effect was studied. UV-Vis spectrophotometer with polarization adjunct was used to measure the polarization character of photosensitive film. The Poly (vinyl cinnamate) (PVCi) film and PVA/Cu2+ film were prepared. They were stretched and photoelastic birefringence formed. Then the oriented films were exposed to UV light. The birefringence decreased under the UV irradiation. The results can be obtained quantitatively by a measurement using polarization spectrometer. The conception of birefringence ratio was presented. The birefringence ratio quantization model was established and the model was attested by experiments.