Photoalignment in Ultrathin Films of a Layer-by-Layer Deposited Water-Soluble Azobenzene Dye

详细信息    查看全文

• 作者：Rigoberto Advincula ; Mi-Kyoung Park ; Akira Baba ; and Futao Kaneko
• 刊名：Langmuir
• 出版年：2003
• 出版时间：February 4, 2003
• 年：2003
• 卷：19
• 期：3
• 页码：654 - 665
• 全文大小：1038K
• 年卷期：v.19,no.3(February 4, 2003)
• ISSN：1520-5827

文摘

The photoalignment of alternate layer-by-layer (LBL) deposited water-soluble azobenzene dye, directred 80 (DR80), and polycations have been investigated. The ultrathin films were probed by polarizedirradiation, UV-vis spectroscopy, and angle-dependent optical retardation measurements using a hybridliquid crystal (LC) cell. Dye aggregates within layers were found to reorient anisotropically with polarizedirradiated visible light. The selective photoisomerization process primarily enhances the E-isomer, givinghigh dichroism with the long axes of the azobenzene dye oriented perpendicular to the polarization vectorof irradiated light (actinic light). The degree of photoalignment was dependent on the number of adsorbedlayers, aggregation behavior, and type of polycation pairs in contrast to spin-coated or Langmuir-Blodgett(LB) films. Atomic force microscopy (AFM) before and after photoisomerization showed lateral expansionof the morphological features consistent with greater anisotropic ordering. These results correlated withthe in-plane azimuthal LC photoalignment behavior in hybrid LC cells. Interesting trends were observed,including thickness-dependent photoalignment behavior, different irradiation stabilities, phase shift, andread-write capabilities as photoactive ultrathin films.