Toru Fujisawa

Light-scattering-mode optical switching and image storage in polymer/liquid crystal composite films by means of photochemical phase transition

Abstract Photochemical phase transition behavior triggered by photoisomerization of a guest azobenzene doped in nematic (N) liquid-crystalline (LC) domains was investigated in isotropic (I) acrylate polymers with alkyl side chains on their surfaces. These polymer/LC composite films were prepared by in situ thermal polymerization-induced phase separation method (thermal PIPS) from their starting mixtures containing a di- and a mono-functional acrylate monomer. Strong light-scattering states of the intrinsic composite films were transformed into complete transparent states by photochemical N–I phase transition of the LC domains within the polymer matrices that was induced by the trans–cis photoisomerization. Recovery process from the transparent state to the initial light-scattering state was strongly influenced by the alkyl side chains. While the composite film with short alkyl side chain acted as an all-optical switching material because the optical switching could be achieved reversibly and repeatedly between the two different optical states, the composite films with long alkyl side chain showed an ability of optical image storage with high contrast based on light-scattering mode.

Reversible optical control of transmittance in polymer/liquid crystal composite films by photoinduced phase transition

We have demonstrated reversible change in transmittance of composite films, which are composed of an isotropic (I) polymer matrix and a host nematic (N) liquid crystal (LC) containing donor–acceptor type azobenzene LCs (AzoLCs) as photoresponsive molecules, by means of reversible phase transition in the LC domain. The composite films were prepared by in situ thermal polymerization-induced phase separation (PIPS) method from their homogeneous mixtures. Photoisomerization of AzoLCs was induced within the polymer network, and the resultant effect brought about isothermal change in transmittance. The photoinduced reversible and repeatable changes between opaque light scattering and clear transparent states were achieved effectively by irradiation with a monochromatic light at 366 nm. These changes are attributed to photochemical N–I phase transition and rapid thermal I–N phase transition in the host LC domain based on reversible change in molecular sharp of the guest AzoLCs. The optical effects were influence...

AN ANALYSIS OF PHOTO-POLYMERIZATION INDUCED PHASE SEPARATION PROCESS IN LIQUID CRYSTAL/POLYMER COMPOSITE FILMS

Abstract The various diacrylates having different alkyl side-chain are systematically synthesized to investigate the relation between solubility in diacrylates for liquid crystals and phase separation process. In order to analyze the kinetics in photo-polymerization induced phase separation for a homogeneous mixture consisted of liquid crystals and monomers, time resolved confocal laser scanning microscopy with a high resolution is used. The difference between binodal decomposition and spinodal decomposition can be observed for the first time in the system of LC/monomer mixture. The occurring either spinodal or binodal decomposition in the phase separation process depends on the number of methylen in side-chains in diacrylates.

P‐66: Molecular Dynamics Simulation of Interface between Liquid Crystal and Polyacrylate with Alkyl Sidechain

We have performed molecular dynamics simulation of interface between liquid crystal and polyacrylate with different alkyl sidechain length, and qualitatively observed the same orientational behavior as experimental results. We also have analyzed the structure of the interface, concretely the distribution of orientational order parameter near the interface and the relationship between orientational direction of liquid crystal molecules and sidechain.

A Study of Reflectivity on the Liquid Crystal/Polymer Composite Films

Abstract We have studied the reflectivity on the liquid crystal/polymer composite films. The reflectivity is remarkably affected by the morphology and the birefringence of liquid crystals. It is expected that paper-like displays are realized by the controlling morphology and using higher birefringence liquid crystals.