Theoretical Study On The Electronic Structure And Conductivity Of Polyaniline, Polyphenylenesulfide And Poly-(Phenylenesulfide Phenylenamine)before And After Doping

Conductive polymer is a very active area of research in recent years. the studies On the structure and conductivity of conductive polymer can contribute to the design and preparation of the new and more useful conductive polymer material. Because of its easy processing, chemical stability and high electrical conductivity after doping, the polyaniline, polyphlene sulpfide and poly-(phenylenesulfide phenylenamine) have been concerned by the chemists. but there is not a systematic theoretical study on the relationship between the structure and the conductivity. Based on the experimental results, we used the neutral and dications polymer as the study model before and after doping, with the method of semi-empirical molecular orbital theory, density functional theory method, combined with periodic boundary conditions oligomers and extrapolation to calculate the polyaniline, polyphenylene sulfide, and the their copolymers such as the geometry and electronic structure, band structure and optical excitation energy, by comparing the geometric structure and band gap of the polymer before and after doping, explaining the relationship between its structure and conductivity.In the experimental, For Polyphenylene sulfide (PPS), polyaniline (PANI) and their copolymers (PPSA), they are electrically neutral the ground state is generally closed shell singlet state before doping; and they can obtained the dication polymer by the oxidative doping (p type). Because it maybe exist closed shell singlet state (bipolaron), open shell singlet and triplet states (polaron) three forms in dication system. Open shell singlet state is multiple references properties, we can use the UHF or UDFT broken symmetry method combined (UHF-BS or UDFT-BS) approximation.We first use of PM3, UPM3, B3LYP and UB3LYP methods to optimize the geometry of the number of different units of PPS, PANI, and PPSA oligomers (n=1-5, from dimer to decamer)respectively before and after doping, by calculating the frequency to find The most stable structures obtained polymer HOMO-LUMO energy gap,the calculation of polymer with different forms of energy band structure, access to relevant polymers HOCO-LUCO band gap Eg by the PM3and B3LYP method with periodic boundary conditions (PBC); it is found that the HOMO-LUMO energy gap and the HOCO-LUCO band gap value of these polymers after doping has significantly decreased compared with that before, qualitative explanation of the experiment phenomenon that the conductivity enhanced after doping, but the quantitative point of view can not be well explained the insulator-conductor transition phenomenon when they are doped. Therefore, in order to better explain this phenomenon, we used the ZINDO//PM3, UZINDO//UPM3-BS, or TD-B3LYP, TD-(UB3LYP-BS) to calculate the S0�'S1vertical excitation energies of PPS, PANI and PPSA with the different oligomers (n=1-5) of before and after doping, and extrapolated the S0�'S1excitation energy of infinite chain polymers. The results showed that the optical excitation energy values of PPS befor and after doping are about3.89eV and1.24eV by TD-(UB3LYP-BS) method, about4.44eV and1.14eV by UZINDO//UPM3-BS method, these are very close to the experimental values of3.9eV and1.2eV, which is well explained quantitatively by the polymer after doping insulator conductor transition phenomenon. As well, the undoped and charge-doped PANI with TD-(UB3LYP-BS) and UZINDO//UPM3-BS two methods extrapolated excitation energy are about3.19eV、0.67eV and4.17eV、1.46eV, experimental value are3.6-3.8eV and1.4-1.5eV; extrapolated excitation energy by TD-(UB3LYP-BS) and UZINDO//UPM3-BS two methods for PPSA and charge-doped PPSA are about3.36eV、4.25eV and1.05eV、0.97eV, respectively, which agree well with the corresponding experimental values>3.5eV and<1.38eV; As a result of the calculation for open shell singlet (two polarons) compared with closed shell singlet closer to the experimental results, and the doped polymer electronic spin density analysis, further confirmed that polarons as the conducting carriers mainly contribute to high conductivity in doped PPS, PANI, and PPSA.There are five chapters in our paper.The first chapter, we introduced the structure of conductive polymers, conductive mechanism, the common doped form and the main fields of application. Then by introduced the structural characteristics and other chemical properties of polyacetylene, polysulfanzene, polyaniline, polyphenylenesulfide and poly(phenylenesulfidephenyleneamine), we propose the design and meaning of our work.The second chapter, we briefly introduced some theoretical calculation method which are used in this paper, including semi-empirical methods, density functional theory and band theory, outlines the basic principles of these methods and the development process. Then, we introduced the specific methods in this article.Chapter Ⅲ to Chapter Ⅴ Results and Discussion section.