关键词: 偶氮苯, 液晶, 异构, 取向, 相转变, 玻璃化转变温度

Abstract: Side chain polymer liquid crystal, poly[ω-(4-methoxy-4-azophenyloxy)hexyl] methacrylate (PMAAZO₆) was synthesized by the reaction of potassium methacrylate and 4-methoxy-4'-(1-bromohexyloxy)azobenzene, then free radical polymerization in THF. The polymer obtained was characterized by GPC, NMR, UV spectra, DSC and optical polarizing microscope. Atypical Schlieren texture was observed. The DSC results showed that T_gof the polymer obtained was 61 ℃, the phase trasition from smectic to nematic phase occurred at 91 ℃, and isotropic temerature was 131 ℃. The film with 2μm thickness was obtained by casting the polymer solution in THFon the clean glass plate. The photoresponsive behavior of the film obtained was examined under different conditions. The UV writing light with λ =366 nm induced phase transition at temperature from room to isotropic temperature. The responsive rate increased as the temperature increased. When polarizing light with λ >400 nm was used as writing light, the mesogenic unit was reoriented consistently by the mechanism of cis to trans transformation, and an ordered domain was formed only below T_gof the polymer, because thermal movement of the polymer segments distroyed the ordered arrangement at the temperatures higher than T_g.

Key words: Azobenzene, Liquid crystal, Isomerization, Orientation, Phase transition, Glass transition temperature