The Concentration And Mobility Of Polaron In Pernigraniline-base Polymer Under Pressure

Polyanilines have much more attention because of its excellent properties,a rich source of material and the prospect of widely Technology applications in conductive polymers, Its conductivity depends primarily on the oxidation of main chain of polyaniline , the higher the degree of oxidation, the stronger conductivity. The redox processes associated with the color change and it is reversible, so the conductivity can be change in a wide range, insulator,semiconductor and metal conductor. Pernigranililine-base (PNB) is the oxidized form of polyaniline, it generated by the emeraldine-base (EB) in which doped with proton acid. To understand the conductivity of polyaniline, We must recognize the carrier type, and its concentration and mobility. Researchers have explored a lot about the conductivity under pressure in the experiments, but its conductive mechanism is no theoretical explanation. We investigated theoretically the relationship between conductivity with pressure of pernigranililine-base.We investigated the oxidized form of polyaniline—pernigranililine-base (PNB) polymer on the basis of the extended Ginder-Epstein model. Firstly, an n-type polaron of pernigraniline-base polymer under different pressure was investigated in an extended Ginder-Epstein model, in which parameter V2,0 was varied to stand for pressure,and analyzed relationship between polaron energy of excitation with pressure, And then Studied relationship between concentration for polarons with pressure; secondly, We studied drift of the polaron in the electric field under high pressure with molecular dynamics simulation, and calculated the mobility of polaron, and then summarized pressure on the conductivity.Firstly, our results showed that: while increasing pressure up to 9.34 GPa, bond-order wave of the polaron had no substantial changes,but the ring-torsion angles of the polymer gradually decreased to zero,excitation energy for a polaron reduced from 1.53eV to 0.99 eV and its concentration increased nine orders of magnitude.Secondly, we used molecular dynamics simulation on the basis of the extended Ginder-Epstein model, while increasing pressure up to 9.34 GPa, the mobility of polaron first increased and then decreased, when pressure was about 4GPa, mobility reached to the maximum 370 cm2/(Vï¹'s); the conductivity increased with the increase of pressure and it increased eight orders of magnitude. Experiments showed that the conductivity of pernigraniline-base polymer with the increase of pressure, Until it reached the saturation when pressure was about 9GPa.