Nanomovement of Azo Polymers Induced by Longitudinal Fields
Nanomovement of Azo Polymers Induced by Longitudinal Fields
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DOI：
10.1021/ph400052b
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发表时间：
2014-03-01
期刊：
影响因子：
7
通讯作者：
Inouye, Yasushi
中科院分区：
文献类型：
--
作者：
Ishitobi, Hidekazu;Nakamura, Issei;Inouye, Yasushi
在偶氮聚合物薄膜中，通过具有纵向场（E-z）的聚焦激光光斑诱导表面变形。我们发现，由E-z诱导的变形模式强烈依赖于聚合物膜的厚度。当膜厚小于37 nm时，聚合物在聚焦点的中心处形成凹陷，而当膜厚大于37 nm时，聚合物形成突起。这些结果意味着向上和向下的力在聚合物膜内部竞争，并且它们之间的平衡最终决定了膜的表面拓扑结构（凹陷与突起）。我们还发现，变形模式依赖于薄膜上的材料的折射率。计算了聚合物薄膜内部的光场分布，并与实验结果进行了比较，发现各向异性光流动力和光梯度力对聚合物的运动都有重要影响。此外，我们发现，通过改变照射光的波长，光学梯度力施加在不偶氮苯部分的侧链，但聚合物的主链有助于聚合物的运动。
Surface deformations were induced in azo-polymer films by a focused laser spot that has a longitudinal field (E-z). We found that the deformation patterns induced by E-z were strongly dependent on polymer film thickness. The polymer formed a dip at the center of the focused spot when the film thickness is thinner than 37 nm, while the polymer formed a protrusion when the film thickness is thicker than 37 nm. These results imply that upward and downward forces are competing inside the polymer film, and the balance between them finally decides the surface topology (dip versus protrusion) of the film. We also found that the deformation patterns were dependent on the refractive index of the material on the film. We calculated the light field distribution inside the polymer film, and by comparing the experimental results we found that both anisotropic photofluidic force and optical gradient force might play important roles in the polymer movement. In addition, we found by changing the wavelength of the irradiation light that optical gradient force exerted on not the side-chain of the azobenzene moiety but the main chain of the polymer contributes to the polymer movement.