Photoreactive Polymers Containing Various Kinds of Cinnamate Groups with Optical Anisotropy

ABSTRACT

Photoreactive polymers with optical anisotropy, which may be applied as the photoalignment layer for liquid crystal display, were synthesized through two-step reaction between several kinds of epoxies and cinnamate groups. The photoreactive polymer film was formed by spin-coating and then exposed to linearly polarized UV light with the wavelength of 254 or 365 nm. The optical anisotropy of the polymer film caused by the selective cycloaddition of the cinnamate groups was confirmed from the polarized UV-vis spectra. The polymer films irradiated by the polarized UV light showed anisotropic absorbance in the polarized UV-vis spectra, while the polymer irradiated by unpolarized UV exhibited isotropic absorbance. We also confirmed the photoreactive polymer film could align liquid crystal. LC cell fabricated using the polymer films irradiated by linearly polarized UV showed anisotropic transmission of the polarized visible light, while the cell fabricated using the polymer films irradiated by unpolarized UV exhibited isotropic transmission.

Keywords:

• cinnamate group
• liquid crystal display
• optical anisotropy
• photoalignment layer
• photoreactive polymer

Acknowledgments

This research was supported by Gyeonggi Province of Korea through the Materials Research Center for Information Display.