Photorefractive Materials

本研究旨在探索设计新型高性能光折变材料的原理。 提出了两类光折变材料：1）高和/或低Tg的全功能化光折变聚合物和2）多功能小分子体系。 这些被提出来测试的想法，共轭聚合物主链将发挥电荷传输剂的作用和中性过渡金属络合物（表现出有趣的金属到配体的电荷转移（MLCT）过程）将发挥电荷产生物种的作用。 这样可以提高电荷产生过程的量子效率，并使暗电流和局域离子偶极场最小化。 因此，所得聚合物的PR性能将得到增强。 建议的聚合物系统的玻璃化转变温度可以微调，使PR聚合物的主要Pockel贡献或克尔贡献可以合成和它们的物理性能进行比较。 影响PR性能的不同参数，如非线性光学发色团，敏化剂和烷基链间隔的变化，将被系统地研究和定义它们的结构/性能相关性。 第二类材料是无定形的、低Tg的小分子系统。 它们是含有PR效应所需的所有功能的单一多功能分子。 这样的系统之一是低聚噻吩-NLO分子：无定形材料，其中低聚噻吩是光电导组分。 这些材料旨在测试多功能小分子系统而不是聚合物可能表现出相当的PR性能的想法。 这些都是结构上定义良好的，简单的系统，用于详细的物理研究。 一个额外的好处是，它们也很容易加工成厚膜。 结合所提出的合成工作，将对这些材料进行详细的物理表征，包括电光测量、光电导研究、迁移率测量、双光束耦合和四波混频实验以及全息成像。 这项工作的意义在于它为新材料的设计和合成提供了新的思路。 将金属配合物引入功能聚合物的想法可能对未来的材料开发至关重要，而不是光折变聚合物系统。 多功能小分子系统的光折变效应的想法也是重要的PR机制的基本理解和实际应用。 在这些材料的合成中开发的新化学将影响聚合物合成界。

9815955YuIn this proposal, the principles of designing novel, high performance photorefractive materials are sought. Two classes of photorefractive materials are proposed: 1) high and or low Tg, fully functionalized photorefractive polymers and 2) multifunctional small molecular systems. These are presented to test the idea that conjugated polymer backbones will play the role of charge transport agent and the neutral transition metal complexes (which exhibit interesting metal-to-ligand charge transfer (MLCT) processes) will play the role of charge generating species. In this way, the quantum efficiency of thecharge generation process can be enhanced and the dark current and local ionic dipole field can be minimized. Thus, the PR performance of resulting polymers will be enhanced. The glass transition temperatures of proposed polymer system can be fine-tuned so that PR polymers with either dominating Pockel contribution or Kerr contribution can be synthesized and their physical properties compared. Different parameters which affect the PR performance, such as variations of NLO chromophores, sensitizers and alkyl chains spacers, will be systematically investigated and their structure/property correlations defined. The second class of materials are amorphous, low Tg small molecular systems. They are single multifunctional molecules containing all of the functionality necessary for PR effect. One of such systems is the oligothiophene-NLO molecules: amorphous materials where the oligothiophene is the photoconductive component. These materials are designed to test the idea that a multifunctional small molecular system, instead of polymers, may exhibit comparable PR performances. These are structurally well defined, and simple systems for detailed physical studies. An extra bonus is that they are also very easily processed into thick films. Coupled with the proposed synthetic work, the detailed physical characterization of these materials will be carried out, including e-o measurements, photoconductivity studies, mobility measurements, two beam coupling and four wave mixing experiments and holographic imaging. %%%The significance of the proposed work is that it provides novel thinking in new material design and synthesis. The idea of introducing metal complexes into functional polymers may prove vital for future material development other than the photorefractive polymer system. The idea of a multifunctional small molecular system for photorefractive effect is also important both for fundamental understanding of the PR mechanism and for practical applications. The novel chemistry developed in the synthesis of these materials will impact the polymer synthetic community.***