Optical Anisotropy Control by Self-Organization of Sorbitol Derivative

The orientation birefringence of atactic polystyrene (PS) was enhanced by the addition of 1,3:2,4-bis-O-(benzylidene)-d-sorbitol (DBS). DBS dissolved in molten PS at a high temperature and was segregated as nanofibers by self-organization during cooling. Under shear, the nanofibers oriented along the flow direction without agglomeration and provided a large negative orientation birefringence with weak wavelength dispersion. Furthermore, the relaxation of optical anisotropy was markedly slow following the cessation of flow and deformation, which was attributed to the slow orientation relaxation of the DBS nanofibers. This is a desirable property for the production of retardation films. To achieve a retardation film with extraordinary wavelength dispersion, a material must show large negative birefringence with weak wavelength dispersion; therefore, the addition of DBS is attractive.