Study On Electro-optic Properties Of Polymer Network Liquid Crystal

Polymer Network Liquid Crystal(PNLC)can be prepared by curing the mixture of the host liquid crystal and polymer monomer,and then polymerizing under the ultraviolet light.The liquid crystal molecules are distributed in the polymer network and formed by the polymerization effect.The optical interface can be generated by the refractive index inconsistency between the polymer and liquid crystal molecules,which has a strong scattering for the incident light and presents an opaque film at voltage-off state.When the appropriate voltage is applied,the orientation vectors of the dielectric anisotropic liquid crystal molecules are arranged along the electric field direction,then the transparent state can be obtained.Thus,PNLC is as optical thin film with scattering opacity and transparency states.The anchoring energy of polymer network on liquid crystal molecules has a decisive influence on the electro-optical characteristics of PNLC film,and it has a great influence on the hysteresis effect and the residual birefringence,as well.The different kinds of polymer monomers have the different structures and physicochemical properties,thus the anchoring energy of the polymer network for liquid crystal molecules is also in-equable.These ultimately result in the different properties for different PNLC films.This work investigated five kinds of polymer monomers with different functional groups and structures.The detailed studies of different UV curing temperature,proportion of light initiator,polymerization of monomers with different proportion on PNLC electro-optical characteristics were in progress.Moreover,the influence of membrane of the parent compound on the improvement of the electro-optical characteristics of PNLC film were investigated.As a result,when the ratio of liquid crystal and polymeric monomers is 12:1,the temperature is 67 ?and the content of RG184 of the light primer is 0.2%,the better electro-optical characteristics can be obtained.The results show that the contrast ratio increases with the increasing curing temperature at UV exposure state.As the temperature is higher,the contrast ratio decreases on the contrary.The more rigid polymeric monomers polymerize,the higher the threshold and operating voltages of PNLC film should be,but there is a shorter response time.The larger the viscosity,the longer the response time can be;The higher the functional degree,the more double bonds will be involved in the curing reaction;The greater the shrinkage,the smaller the polymer mesh aperture can be formed,and the faster response time can be achieved.Besides,as the polyoxyethylene sorbitan dehydration single oleate(TWEEN 80)was added into the PNLC matrix,the threshold voltage and operating voltages can be reduced by ?5×.Besides,there are some other improvements,such as hysteresis effect and contrast ratio.After attempt,as the mixture ratio is 10:1 for monomer and TWEEN 80,the comprehensive electro-optic properties of PNLC are best under the condition of different PNLC thicknesses.This work provides the theoretical and experimental bases for further investigation of polymer monomer,and the needed PNLC film can be prepared based on the investigated contents.It has an important guiding significance for the future design of PNLC film.