First Principles Study Of Polyphenylene Sulfide And Its Derivatives

Due to stabile conjugated π electrons having the characteristic of quite strong delocalization and polarization, poly-para-phenylene sulfide (PPS), one of conducting polymers, has been widely applied in electricity, magnetism, optics and so on, for example, light emitting diodes (LEDs), field effect transistors (FETs) and nonlinear optical devices. It also has been extensively applied in structural functional macromolecule materials, because of rigidity structure having possessed the feature of high temperature, strong chemical inertness, high flame-retardant, considerable mechanical properties, wonderful dimension stabilization and excellent performance of electricity, etc.We perform ab initio density functional theory to investigate the structural and electronic properties of isolated and crystalline PPS. First, using the GGA approximation for the exchange-correlation potential, the optimal structure for an isolated PPS are generally in good agreement with the theoretical and experimental results, but the band gap is less than the experimental data and it is general fault to calculate the semiconductor materials using local density approximation; From electronic properties of isolated PPS, we can conclude mat by inserting heteroatom sulfur between the phenyl groups, the degree of delocalization of the π electrons is supposed to be reduced, however, the appreciable delocalization of the π electrons along the PPS chain still exists. In crystalline state, we find that intrachain interactions have a significant effect on band structure and density of states, comparing to isolated chain. Then, the ground states of configuration about other polyarylene sulfides are shown and their mechanics properties of Young's modules have also been studied. The results of Young's modules are larger than experimental data, because of our calculating in 0 K, and experimental data in room temperature. In the end, the electronic properties of PPS and PBT, which is formed by PPS doping, are compared and the conductivity of PBT is greater than PPS.