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首页> 外文学位 >Photonic properties of self-assembled organic materials: Supramolecular films, and nanoribbon-templated gels and polymers.
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Photonic properties of self-assembled organic materials: Supramolecular films, and nanoribbon-templated gels and polymers.

机译：自组装有机材料的光子特性：超分子薄膜以及纳米带模板的凝胶和聚合物。

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摘要

Photonic properties were studied in two self-assembled systems: supramolecular rodcoil self-assemblies, and materials templated with dendron rodcoil (DRC) nanoribbons. A rodcoil molecule contains covalently connected rod-like and coil-like segments. The aggregation of rodcoils forms supramolecular polar layered structures with ∞mm symmetry. Nonlinear optical properties of these materials are determined by their molecular characteristics. Several sets of architecturally similar but chemically different rodcoils were studied, and their nonlinear susceptibility was found strongly influenced by molecular hyperpolarizability and layer spacing of the supramolecular materials formed by these molecules. The macroscopic polarization of these materials is relatively low, possibly caused by polydomain structures. To improve the polarization, glass substrates were patterned with periodic arrays of squares with lateral dimensions of 7 and 17μm, created by focused ion beams. The average molecular tilt angle was found smaller in the films on patterned substrates, suggesting that substrate micropatterning enhances overall polarization in these supramolecular films. DRC molecules contain covalently connected dendritic, rod-like, and coil-like segments, and form gels with certain monomers and solvents like styrene or 2-ethylhexyl methacrylate (EHMA). Gelation is triggered by the self-assembly of DRC molecules into a network of ribbon-like nanostructures that are 10nm wide, 2nm thick, and up to 10μm long. DRC nanoribbons improve chain orientation in stretched DRC-polystyrene samples polymerized from DRC-styrene gels, compared with pure polystyrene stretched to the same extent. Linear-shape dyes show significantly larger emission polarization when incorporated in stretched DRC-polystyrene than in stretched pure polystyrene. When subject to a DC electric field, DRC-EHMA gels undergo electrophoresis, creating solid films consisting mostly of oriented DRC nanoribbons. The poled nanoribbon film shows uniform birefringence, and the nanoribbons are oriented along the poling field, suggested by TEM studies of ultramicrotomed samples. DRC gelation process disperses inorganic nanocrystals like ZnO, forming a stable nanocrystal-nanoribbon hybrid material. Similar electrophoresis occurs to the gel containing ZnO, orienting both nanoribbons and ZnO nanocrystals along the poling field. The poled DRC-ZnO film generates ultraviolet lasing emissions, with greatly lowered threshold compared with pure ZnO nanocrystals.
机译：在两个自组装系统中研究了光子特性：超分子棒状线圈自组装和以树枝状棒状线圈（DRC）纳米带为模板的材料。棒状分子包含共价连接的棒状和线圈状链段。棒状线圈的聚集形成具有∞mm对称性的超分子极性分层结构。这些材料的非线性光学特性取决于它们的分子特性。研究了几套在结构上相似但化学上不同的棒状线圈，发现它们的非线性敏感性受分子超极化性和由这些分子形成的超分子材料的层间距的强烈影响。这些材料的宏观极化相对较低，可能是由多畴结构引起的。为了改善偏振，玻璃基板被图案化，形成正方形的周期性阵列，其横向尺寸为7和17μm，由聚焦离子束产生。发现在图案化基底上的膜中平均分子倾斜角较小，这表明基底微图案化增强了这些超分子膜中的整体极化。 DRC分子包含共价连接的树枝状，棒状和线圈状链段，并与某些单体和溶剂（如苯乙烯或甲基丙烯酸2-乙基己酯）形成凝胶。 DRC分子自组装成带状纳米结构的网络会触发胶凝，该结构为10nm宽，2nm厚，最长10μm。与以相同程度拉伸的纯聚苯乙烯相比，DRC纳米带改善了从DRC-苯乙烯凝胶聚合而来的拉伸DRC-聚苯乙烯样品的链取向。当掺入拉伸的DRC-聚苯乙烯中时，线形染料显示出比拉伸的纯聚苯乙烯中显着更大的发射极化。当受到直流电场作用时，DRC-EHMA凝胶会进行电泳，从而形成主要由定向DRC纳米带组成的固体膜。极化的纳米带膜显示出均匀的双折射，并且纳米带沿着极化场取向，这是超微切片样品的TEM研究表明的。 DRC凝胶化工艺可分散无机纳米晶体（如ZnO），形成稳定的纳米晶体-纳米核杂化材料。包含ZnO的凝胶发生类似的电泳，沿着极化场定向纳米带和ZnO纳米晶体。极化的DRC-ZnO薄膜会产生紫外线发射，与纯ZnO纳米晶体相比，其阈值大大降低。

著录项

  • 作者

    Li, Leiming.;

  • 作者单位

    University of Illinois at Urbana-Champaign.;

  • 授予单位 University of Illinois at Urbana-Champaign.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2002
  • 页码 158 p.
  • 总页数 158
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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