Electronic Structure of Pristine and Highly Doped Conducting Polymers

点击翻译按钮获取中文摘要

9802300 Kertesz This is a theoretical research grant which is funded jointly by the Divisions of Materials Research and Chemistry. The research focuses on two fundamental aspects of conducting conjugated polymers. First, theoretical guidelines will be developed in order to answer the question: Is there a minimum bandgap in this family of novel materials? Despite worldwide efforts to attain a bandgap of 0.5eV or less in conjugated polymers, very few examples of bandgaps exist that are significantly below 1 eV. While attaining a small bandgap in a conducting polymer will probably lead to interesting applications, this problem presents a profound challenge in its own right which is of broad interest. The design of new materials with the desired small bandgap will be possible only through systematic determination of the factors influencing the structure and electronic properties of electroactive polymers including the contributions of heteroatoms and side groups, the effects of topology (ladders, rings, etc), the influence of coplanarity and other conformational degrees of freedom. This leads to the second aspect. The effects of interchain interactions are notoriously difficult to treat theoretically. In this research a fundamental aspect of this problem will be attacked in a novel fashion: the experimental vibrational spectra will be used to obtain the value of interring torsion that would be too sensitive to calculate purely theoretically, but cannot be obtained from experiment. Accurate modeling of IR and Raman spectra, including intensities, as a function of interring coupling, will allow the determination of critical structural data, such as interring bond distances and torsion. Currently, there is a lack of a unified approach in the theoretical modeling of the structure, vibrational spectra and electronic structures of conducting polymers. This project will provide a versatile testing ground for the critical evaluation of various non-local densit y functionals and their applications to organic polymeric materials. Applications include the main types of conjugated polymers. %%% This is a theoretical research grant which is funded jointly by the Divisions of Materials Research and Chemistry. The research focuses on two fundamental aspects of conducting conjugated polymers. First, theoretical guidelines will be developed in order to answer the question: Is there a minimum bandgap in this family of novel materials? Also, the effects of interchain interactions are notoriously difficult to treat theoretically. Thus, second, in this research a fundamental aspect of this problem will be attacked in a novel fashion: the experimental vibrational spectra will be used to obtain the value of interring torsion that would be too sensitive to calculate purely theoretically, but cannot be obtained from experiment. The results of this research should lead to a better understanding of an important class of materials. ***