| The polymer/liquid crystal composite material is a two-phase system containing liquid crystal and polymer.Due to the special photoelectric anisotropy characteristics of liquid crystal materials,polymer/liquid crystal composite materials can respond to an external electric field and freely switch between a transparent state and an opaque state.The polymer/liquid crystal composite material has a simple preparation process and stable performance,and can be made into a large-sized flexible device.It not only has many applications in smart dimming glass,optical modulators,and flexible displays,but also has huge potential in the field of aircraft strong light protection.Polymer dispersed liquid crystal is the focus of the current development of electrically driven color changing materials.However,the current polymer/liquid crystal composite film has a low contrast and a narrow optical modulation band,which hinders the practical application of the material.On the other hand,the theoretical research on the optical response of the polymer/liquid crystal composite film to the external field is relatively slow,and it has limited guidance for further optimizing the electro-optic modulation properties of the polymer/liquid crystal composite material.Therefore,how to better analyze the optical response mechanism of polymer/liquid crystal composite materials,and then improve the electro-optic modulation performance of the materials is an urgent problem to be solved in the development of polymer/liquid crystal composite materials.In response to the above problems,this paper adopts the method of polymerization induced phase separation to develop a new polymer/liquid crystal composite film with high contrast and wide optical band modulation by compounding with functional nanomaterials.Polymer/liquid crystal composites are divided into polymer dispersed liquid crystals and polymer stabilized liquid crystals.First,the optical response characteristics of the two materials are analyzed.For polymer dispersed liquid crystals,starting from the effect of external field free energy and elastic free energy on the direction of liquid crystal droplets,the relationship function between the order parameters of liquid crystal droplets and the external field is obtained.Furthermore,the change of the ordered parameters of polymer dispersed liquid crystal with the external field is simulated.From the thermodynamic point of view,the response behavior of the polymer stabilized liquid crystals to the external field is analyzed.The distribution of the liquid crystal director under the external field is simulated.The study of optical response characteristics enriches the theoretical system of polymer/liquid crystal composite films,and provides the necessary theoretical basis and guidance for the optimization of electro-optic modulation properties of materials.Then the polymer/liquid crystal composite material with high contrast is prepared by the multiple texture conversion of cholesteric liquid crystal,and the influence of chiral additive content on the electro-optic performance of the polymer/liquid crystal composite film is studied.The electro-optical test results show that the optimal addition amount of the chiral additive is 4wt%,the on-state transmittance of the polymer dispersed liquid crystal with this addition is only 3.2%,and the contrast ratio reaches 19.17.After adding 4wt% of chiral additives,the threshold voltage of polymer stabilized liquid crystal dropped significantly.When the on-state transmittance was basically unchanged,the offstate transmittance decreased by as much as 20%,and the contrast reached 14.41.The polymer/liquid crystal composite film based on cholesteric liquid crystal greatly improves the electro-optic performance of the material.Finally,the inorganic semiconductor nanoparticles of antimony tin oxide with ultraviolet and infrared light shielding properties are doped into the polymer dispersed liquid crystal to prepare a polymer dispersed liquid crystal film with wide optical band modulation.The addition of nanoparticles leads to a decrease in the threshold voltage of polymer dispersed liquid crystals,which further optimizes the electro-optic performance and enhances the applicability of polymer dispersed liquid crystal films.At the same time,without affecting the visible light transmittance,the doping of tin antimony oxide effectively improves the optical shielding effect of the polymer dispersed liquid crystal in the infrared band,in which the near infrared shielding effect is greatly increased,and the average transmittance is from 28% fell to 13%,and the largest fell from ～42% to 15%.The transmittance of the sample in the mid-infrared band gradually decreases to a stable value as the content of antimony tin oxide increases.A novel polymer dispersed liquid crystal material with broad-band optical modulation of ultraviolet-visible-infrared light was developed by doping. |
PDF Full Text Request