Sullivan Philip A, Rommel Harrison, Liao Yi, Olbricht Benjamin C, Akelaitis Andrew J P, Firestone Kimberly A, Kang Jae-Wook, Luo Jingdong, Davies Joshua A, Choi Dong Hoon, Eichinger Bruce E, Reid Philip J, Chen Antao, Jen Alex K-Y, Robinson Bruce H, Dalton Larry R
Department of Chemistry and Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98105, USA.
J Am Chem Soc. 2007 Jun 20;129(24):7523-30. doi: 10.1021/ja068322b. Epub 2007 May 25.
Extensive experimental and theoretical study suggests that interchromophore electrostatic interactions are among the most severe impediments to the induction and stability of large electro-optic coefficients in electric-field-poled organic materials. In this report, multichromophore-containing dendritic materials have been investigated as a means to minimize unwanted attenuation of nonlinear optical (electro-optic) activity at high chromophore loading. The dendritic molecular architectures employed were designed to provide optimized molecular scaffolding for electric-field-induced molecular reorientation. Design parameters were based upon past experimental results in conjunction with statistical and quantum mechanical modeling. The electro-optic behavior of these materials was evaluated through experimental and theoretical analysis. Experimental data collected from the dendrimer structures depict a reasonably linear relationship between chromophore number density (N) and electro-optic activity (r(33)) demonstrating a deviation from the dipolar frustration that typically limits r(33) in conventional chromophore/polymer composite materials. The observed linear dependence holds at higher chromophore densities than those that have been found to be practical in systems of organic NLO chromophores dispersed in polymer hosts. Theoretical analysis of these results using Monte Carlo modeling reproduces the experimentally observed trends confirming linear dependence of electro-optic activity on N in the dendrimer materials. These results provide new insight into the ordering behavior of EO dendrimers and demonstrate that the frequently observed asymptotic dependence of electro-optic activity on chromophore number density may be overcome through rational design.
广泛的实验和理论研究表明，发色团间的静电相互作用是电场极化有机材料中诱导和稳定大电光系数的最严重障碍之一。在本报告中，对含多发色团的树枝状材料进行了研究，作为在高发色团负载下最小化非线性光学（电光）活性不必要衰减的一种手段。所采用的树枝状分子结构旨在为电场诱导的分子重取向提供优化的分子支架。设计参数基于过去的实验结果，并结合统计和量子力学建模。通过实验和理论分析评估了这些材料的电光行为。从树枝状聚合物结构收集的实验数据描绘了发色团数密度（N）与电光活性（r(33)）之间合理的线性关系，这表明与通常限制传统发色团/聚合物复合材料中r(33)的偶极受挫情况有所不同。观察到的线性相关性在比分散在聚合物主体中的有机非线性光学发色团体系中实际可行的发色团密度更高时依然成立。使用蒙特卡罗建模对这些结果进行的理论分析重现了实验观察到的趋势，证实了树枝状聚合物材料中电光活性对N的线性依赖性。这些结果为电光树枝状聚合物的有序行为提供了新的见解，并表明通过合理设计可以克服电光活性对发色团数密度常见的渐近依赖性。
