Characterization And Control Of Polymer Network Deformation And Its Effect On Electric-optic Properties In Polymer-stabilized Cholesteric Texture

In polymer-stabilized cholesteric texture (PSCT), polymer network can often be distorted during operation effectively changing the network's morphology. The polymer network deformation could result in the changes as follows: LC director distribution, pitch gradient, and anchoring energy of the polymer network, etc., which have a critical influence on the optical properties of PSCT. However, the characterization of polymer network deformation is difficult due to the tiny polymer network dimensions. The polymer network's morphology can be observed by using SEM and confocal microscopy. However, these methods will not work well when the polymer network exhibits transient distortion and would normally destroy the PSCT device.The dynamic response of PSCT is derived from local director reorientation governed by dielectric coupling effect/self-assembly and polymer network deformation.The double exponential equation well fit the measured data of dynamic response time(R2>99%). By simulating the dynamic response processes of reverse-mode PSCT via double exponential rise/decay model, the deformation of polymer networks were quantitatively characterized.Polymer network deformation can be controlled by regulating the electric field strength, frequency of driving signals, ambient temperature and monomer concentration. Within a certain range, decreasing the intensity of electric field,increasing the driving signal frequency, lowering ambient temperature or increasing monomer concentration could decrease the extent of the polymer network deformation,respectively. Smaller polymer network deformation and faster response speed of the polymer network deformation can effectively restrain the hysteresis effect and shorten field-off response time. These results provide useful guidelines for future PSCT fabrication and performance optimization.