ABSTRACT:The aggregation structure and electro-optical properties of polymer/liquid crystal (LC) composite films were investigated. The aggregation structure of the composite film strongly depended on the components ratio of matrix polymer and low molecular weight liquid crystalline materials. The continuous LC phase was formed in a three dimensional polymer network when the LC weight fraction was above around 50wt%. Also, the aggregation structure of the composite film could be controlled by controlling the solvent evaporation velocity during the film preparation process. The finer matrix polymer fibrils were formed in the case of the faster solvent evaporation velocity. The composite films exhibited reversible light scattering-light transmission switching upon electric ·field -OFF and -ON states, respectively. The light scattering properties of the composite film with a continuous LC phase were strongly dependent on the spatial distortion of nematic directors as well as the mismatch in refractive indices between matrix polymer and LC upon an electric field -OFF state. By controlling the polymeric wall thickness of the composite film below the wavelength (632.8nm) of an incident He-Ne laser beam, the composite films which show a remarkably high transmittance and contrast were successfully realized. The polymer/liquid crystal (LC) composite films developed by Kajiyama et al. In 1979 1 have continuous LC channels in a three dimensional polymer network in the case of the LC weight fraction above around 50wt%. Since the matrix polymer mechanically supports the LC phase and protects it from the environment, this composite film was named as the self-supported LC (SSLC) or the bicontinuous LC (BCLC) film. The SSLC composite film could be prepared by the water-casting method. 2 Anisotropic electric and optical characteristics of the LC materials have been widely applied to various electro-optical systems. The most common LC display system is twisted-nematic (TN) system. 3 This TN system is based on the principle that the twisted LC alignment can rotate the plane of the polarized light by 90°. This system needs two polarizers that cause a low contrast and a narrow view angle. Another important invention for the LC display of nematic LC was the use of dynamic scattering mode (DSM). 4 In this system, the application of a high-enough electric field induces the light scattering by the turbulence of LC which is caused by an electric current effect. LC displays with large-area, high contrast and wide-view angle have been requested for a long time. For the past around 10 years, new types of LC display devices being composed of (polymer/LC) composite films, nematic curvilinear aligned phase (NCAP), 5 > polymer dispersed LC (PD LC), 6 and SSLC 7 -10 >
An estimate for the amount of singlet, triplet and quintuplet character of the wavefunction of a nearest-neighbour pair of spins in a two-sublattice Heisenberg antiferromagnet of spin-1 molecules has been made. The results are applied to Ic-oxygen.
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