Photoinduced reorientation and polarization holography in photo-cross-linkable liquid crystalline polymer films with large birefringence

✍ Scribed by Nobuhiro Kawatsuki; Ayumi Yamashita; Mizuho Kondo; Taro Matsumoto; Tatsutoshi Shioda; Akira Emoto; Hiroshi Ono

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 688 KB
• Volume: 51
• Category: Article
• ISSN: 0032-3861
• DOI: 10.1016/j.polymer.2010.04.043

✦ Synopsis

A new photo-cross-linkable liquid crystalline polymer (PLCP) comprised 4-methoxycinnamoyloxy groups connected with a bistolane side group was synthesized to investigate thermally enhanced photoinduced molecular reorientation of a thin film with linearly polarized (LP) 365 nm light exposure. Due to the axisselective photoreaction of the cinnamate groups followed by the thermally induced self-organization, large molecular reorientation parallel to the polarization of LPUV light (S > 0.6) and large birefringence at the non-resonance region (Dn ¼ 0.34 at 632.8 nm) were obtained. The obtained Dn value is the largest among transparent PLCPs in the visible region. The influence of the degree of photoreaction and the annealing temperature on the thermally enhanced molecular reorientation behavior was explored in detail. Finally, for an application of thin optical devices using the PLCP films, pure polarization holographic gratings with large birefringence, which showed periodic molecularly oriented structure, were fabricated using a 325 nm HeeCd laser in various polarization modes and characterized their optical properties.