Preparation And Properties Of Nano-silica Modified Polymer Liquid Crystal Composite Films

Liquid crystal polymer film has both the thermo-color effect of liquid crystals and the film-forming properties of polymers.The material absorption of infrared light is improved by the modified of nano-silica and the modified liquid crystal composite film can be used in the field of infrared detectors.In this paper,the NOA65,RM257/MMA,PVA and RM257/V40BC are used as polymer substrates.According to the formation of chiral nematic liquid crystals based on the adulteration of chiral compounds S811 and nematic liquid crystal 5CB,the liquid crystal composite films with different polymer substrates were prepared by the the modification of nano-silica.The film properties are characterized by FTIR,POM,SEM,DSC,TGA and XRD.The main researches are as follows:?1?In this study,the NOA65 is used as the prepolymer and the chiral nematic liquid crystals formulated with 5CB and S811 is used as the liquid crystal source.The three kinds of NOA65-based polymer dispersed liquid crystal films are successfully prepared by UV polymerization.Then,this paper studies the effect of nano-SiO₂ on the properties of films by adopting the modification of nano-silica.The results show that nano-SiO₂ expands the infrared absorption range of the film,improves the compatibility between the components in the film and reduces the crystallinity of the film.Furthermore,the maximum thermal decomposition temperature of the modified film increases from 349.9?to 618.7?and the maximum weight loss rate of films decreases from 95.2%to 82.2%.?2?In this study,the RM257 and MMA are used as the prepolymer and a chiral nematic liquid crystal prepared by 5CB and S811 as a liquid crystal source.The three kinds of RM257-MMA-based polymer dispersed liquid crystal films are successfully prepared by UV polymerization.Then,this paper studies the effect of nano-SiO₂ on the properties.The results show that nano-SiO₂ expands the infrared absorption range of the film and reduces the compatibility and crystallinity of the components in the film and the maximum thermal decomposition temperature of the modified film increases from 444.2?to 451.4?.?3?In this study,PVA is used as the prepolymer and a chiral nematic liquid crystal prepared by 5CB and S811 is used as the liquid crystal source.The nano-SiO₂prepared by the sol-gel method is used to modify the film and adds hexadecyl trimethyl ammonium bromide?HTAB?and ethyl trimethoxysilane?ECETMS?to the films.By this way,the properties of the film can be characterized.The results show that the compatibility of Nano-SiO₂/PVA/LC film is improved greatly by introducing ECETMS in the composite system.This paper finds that the film has excellent dual-band mid-infrared absorption performance by FTIR and the melting point of composite is improved in the bands of 3.0 to 3.2?m and 8.2 to 10.8?m and the highest absorption rate is 99.0%.Compared with the pure PVA film,the melting point of composite film increases from 90.3?to 135.2?.This paper finds that by adding the modification of ECETMS,the Electro-optical performance is obviously improved base on the analysis of the Electro-optical performance of PDLC.And when the voltage is 16V,the transmittance of the film can reach to 86.7%.?4?In this study,V40BC and RM257 are used as prepolymers,the thermotropic nematic liquid crystal polymer is synthesized based on one-process step.The chiral nematic liquid crystal and nano-silica are prepared from the adulteration of nematic liquid crystal 5CB and chiral agent S811.Then,this paper studies the properties of the modified liquid crystal composite film after its modification.The results show that the film is modified by chiral nematic liquid crystal crystal and nano-SiO₂base on adulteration of them and the thermal stability of the film is improved after modification.