Control of Dispersion and Shapes of Metallic Nano-particles Generated in Polymer-metal Complex Systems and Development of Functional Materials for Optical Devices.

观察到单轴拉伸和银分散聚酰亚胺薄膜在可见光和近红外区的光学透过率各向异性。用一步法制备了聚酰胺酸膜，即用6~25mol%的硝酸银溶液对聚酰胺酸膜进行热固化和单轴拉伸。在固化过程中，具有棒状结构的聚酰亚胺链沿拉伸方向取向，并伴随着细长形状的银纳米粒子的析出。对于厚度为14.8μm、透过率为80%垂直于拉伸方向的薄膜，在850 nm处获得了大于320：1(25db)的透过率各向异性，并且在150℃下热处理1h后仍保持其光学性质。这种薄膜满足了将薄膜偏振器插入硅基波导中形成的凹槽中的所有要求。另一方面，以含金属盐或有机金属络合物的聚酰胺酸S为原料，采用热固化法制备了含8种金属(Au、Ag、Pd、Cu、Al、Co、Fe、Ni)的氟化聚酰亚胺薄膜。考察了金属粒子的化学状态、平均尺寸和空间分布，并与主体聚酰亚胺薄膜的热性能和光学性能进行了比较。析出的金属粒子增加了聚酰亚胺的平均折射率。所有薄膜在可见光区的透明度都比主体聚酰亚胺低得多。然而，除含金薄膜外，其他含金属薄膜在近红外区(1550 Nm)的透过率均大于80%。观察了由六氟乙酰丙酮钴制备的聚酰亚胺在磁场作用下入射光的偏振旋转。这可以看作是含钴纳米粒子引起的光学法拉第效应。

Anisotropy in optical transmittance in the visible and near-infrared region was observed for uniaxially drawn and silver-dispersed polyimide films. The films were prepared in a one step operation, that is thermal curing and simultaneous uniaxial drawing of poly(amic acid)films dissolving 6〜25mol% of silver nitrate. The polyimide chains having a rod-like structure were oriented along the drawing direction during curing accompanying with the precipitation of silver nano-particles having elongated shapes. An anisotropy in transmittance of larger than 320 : 1(25dB)was obtained for a 14.8μm-thick film at 850nm with an transmittance of 80% perpendicular to the drawing direction, and its optical properties were retained after annealing at 150°C for 1h. This film suffices all the requirements for a thin-film polarizer inserted into a groove formed in silica-based waveguides. On the other hand, eight kinds of metal(Au, Ag, Pd, Cu, Al, Co, Fe, Ni)containing fluorinated polyimide films were prepared by thermal curing of poly(amic acid)s containing metallic salts or organo-metallic complexes. The chemical states, average sizes, and spatial distribution of the metallic particles were examined, and the thermal and optical properties of the films were compared with those of the host-polyimide. The precipitated metal particles increase the averaged refractive indices of the polyimides. All the films showed much less transparency in the visible region than the host-polyimide. However, the metal-containing films, except for the gold-containing film, showed transmittance higher than 80% in the near-infrared region(at 1550nm). Rotation of polarization of incident light was observed for a polyimide prepared from cobalt(hexafluoroacetylacetonate)by applying a magnetic field. This can be regarded as the optical Faraday effect caused by cobalt-containing nano-particles.