Kinetics and Characterization of Preparing Conductive Nanofibrous Membrane by In-situ Polymerization of Polypyrrole on Electrospun Nanofibers

Abstract Polypyrrole (PPy) is a conductive polymer that can be fabricated into various structures via in-situ polymerization for different applications. However, a kinetics study of its in-situ polymerization is needed for a better understanding of the mechanisms of pyrrole polymerization. This paper develops two different kinetics models based on existing PPy polymerization mechanisms. The most suitable mechanism is first identified by comparing the model results with experimental data. Then, in-situ polymerizations of PPy on electrospun fibrous polyacrylonitrile (PAN) templates were produced at temperatures ranging from 273 to 285 K. The results show that the overall reaction rate of the in-situ polymerization process in the presence of electrospun fibrous template is faster than that without the template. Further investigation confirms that the increase in the overall reaction rate is attributed to the enhanced reactions between oxidized pyrrole oligomers and neutral pyrrole monomers, as the corresponding reaction rate constant and activation entropy increased by 158.2-209.6% and 37.7%, respectively. The reason is that the considerable number of available reaction sites between oxidized oligomers and neutral monomers are created by the fibrous template. In addition, the composite membrane obtained from the in-situ polymerization exhibited well-developed fibrous nanostructure, good electrical conductivity (0.29 ± 0.04 S∙m-1), sufficient mechanical strength (UTS of 8.7 MPa) and relatively stable thermal properties (up to 250°C).