Highly Photosensitive Surface Relief Gratings Formation in a Liquid Crystalline Azobenzene Polymer: New Implications for the Migration Process

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• 作者：Nobuyuki Zettsu ; Toshinobu Ogasawara ; Ryusuke Arakawa ; Susaku Nagano ; Takashi Ubukata ; Takahiro Seki
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：June 26, 2007
• 年：2007
• 卷：40
• 期：13
• 页码：4607 - 4613
• 全文大小：221K
• 年卷期：v.40,no.13(June 26, 2007)
• ISSN：1520-5835

文摘

We have recently demonstrated a markedly photosensitive surface relief gratings (SRG) formationin thin films of liquid crystalline azobenzene-containing polymers, which proceeds from a cis-rich state of theazobenzene [Zettsu et al. Adv. Mater. 2001, 13, 1693; Macromolecules 2004, 37, 8692]. Such polymers exhibitedunexpected enhancements in the sensitivity to light for the completion of SRG formation, the required energydose being ~10³-fold lower than that for other azobenzene polymers systems widely employed. Here we reportdetailed results on the systematic explorations for understanding the migration mechanism. The cis-isomer contentat the initial state and irradiation intensity crucially influenced the migration efficiency and the resulting reliefstructure in nonlinear manners. The Zisman plot showed that the light irradiation leads to a large change in thecritical surface tension. Such results strongly suggest that the photochemically induced phase transition and theresulting spatial modulations in the physical properties in the film play the essential roles for the SRG formation.On the basis of this knowledge, the SRG formation via a sensitized excitation was demonstrated for the first timeby incorporation of a near-infrared absorbing dye.