Photoinduced optical anisotropy and reorientation in copolymers containing 4-methoxyazobenzene side groups and methyl methacrylate units using linearly polarized 633 nm light
Photoinduced optical anisotropy and reorientation in copolymers containing 4-methoxyazobenzene side groups and methyl methacrylate units using linearly polarized 633 nm light
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DOI：
10.1016/j.polymer.2006.02.004
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发表时间：
2006-03
期刊：
影响因子：
4.6
通讯作者：
E. Uchida;N. Kawatsuki
中科院分区：
文献类型：
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作者：
E. Uchida;N. Kawatsuki
合成了含有4-甲氧基偶氮苯侧基和甲基丙烯酸甲酯单元的液晶（LC）和非LC共聚物，利用薄膜的偏振吸收光谱比较光致重取向行为。用非偏振的365 nm光照射使共聚物膜中的Z-异构体饱和，随后暴露于线性偏振（LP）的633 nm光，基于轴选择性的Z-至-E光异构化，对于所有Z-异构体膜产生光诱导光学各向异性（ΔA）。当共聚物不表现出LC性质时，ΔA逐渐增加，直到60-80mol%的Z-异构体异构化为E-异构体，但随着进一步的光异构化反应而降低。另一方面，对于LC共聚物，膜的光诱导ΔA的大小持续增加，直到E-异构体形成饱和。对于LC共聚物，观察到光诱导ΔA的热放大，但是对于非LC共聚物，热处理导致光诱导ΔA消失。轴向选择性的Z-to-E光异构化保持了两种异构体的跃迁矩的方向，导致了光诱导ΔA，并在Z-to-E光异构化过程中增加了膜的液晶性质，以诱导介晶基团的自组织。
Liquid crystalline (LC) and non-LC copolymers that contain 4-methoxyazobenzene side groups and methyl methacrylate units were synthesized to compare the photoinduced reorientation behavior using the polarization absorption spectra of thin films. Irradiating with non-polarized 365nm light saturated the Z-isomer in the copolymer films and subsequent exposure to a linearly polarized (LP) 633nm light generated a photoinduced optical anisotropy (ΔA) for all Z-isomer films based on an axis-selective Z-to-E photoisomerization. When a copolymer did not exhibit a LC nature, ΔA gradually increased until 60–80mol% of the Z-isomers isomerized to the E-isomers, but decreased upon further photoisomerization reaction. On the other hand, the magnitude of the photoinduced ΔA of a film continuously increased for LC copolymers until E-isomer formation was saturated. Thermal amplification of the photoinduced ΔA was observed for LC copolymers, but the thermal treatment resulted in the disappearance of the photoinduced ΔA for the non-LC copolymers. The axis-selective Z-to-E photoisomerization that preserves the direction of the transition moment of both isomers caused the photoinduced ΔA and increased the liquid crystalline nature of the film during the Z-to-E photoisomerization to induce the self-organization of the mesogenic groups.