Photorefractive Materials

9815955Yu在这个方案中，寻求设计新型、高性能光折变材料的原则。提出了两类光折变材料：1)高、低玻璃化温度的全功能化光折变聚合物；2)多官能团小分子体系。这些都是为了验证共轭聚合物主链将扮演电荷传输剂的角色，而中性过渡金属络合物(表现出有趣的金属到配体电荷转移(MLCT)过程)将扮演电荷产生物种的角色。这样，可以提高电荷产生过程的量子效率，并且可以最小化暗电流和局域离子偶极场。因此，所得聚合物的PR性能将得到提高。所提出的聚合物体系的玻璃化转变温度可以微调，从而可以合成以Pockel贡献和Kerr贡献为主的PR聚合物，并比较它们的物理性能。系统地研究了影响PR性能的不同参数，如NLO生色团、敏化剂和烷基链间隔基的变化，并定义了它们的结构/性质关联。第二类材料为无定形、低玻璃化温度的小分子体系。它们是单一的多功能分子，包含PR效应所需的所有官能团。这样的体系之一是寡硫苯-NLO分子：无定形材料，其中寡硫苯是光导成分。这些材料旨在测试多功能小分子体系而不是聚合物可能具有类似的公关性能的想法。它们在结构上定义得很好，而且是用于详细物理研究的简单系统。一个额外的好处是，它们也很容易加工成厚膜。除了拟议的合成工作外，还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、两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。将金属络合物引入功能聚合物的想法可能被证明对未来材料的发展至关重要，而不是光折变聚合物系统。多功能光折变小分子体系的概念对于从根本上理解光折变机理和实际应用都是非常重要的。在这些材料的合成中发展起来的新化学将对聚合物合成社区产生影响。

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.***