Fabrication of electrically-conducting nonwoven porous mats of polystyrene-polypyrrole core-shell nanofibers via electrospinning and vapor phase polymerization

This paper describes the growth of polypyrrole (PPy) layers over polystyrene (PS) nanofibers via a vapor phase polymerization process. PS nanofibers were produced through electrospinning of PS solutions containing chemical oxidants capable of polymerizing pyrrole monomers. The electrospun PS nanofibers provided a robust and stable template for growth of conducting polymer nonwoven porous mats. A mixture of tetrahydrofuran, acetone, and butanol was able to dissolve both hydrophobic PS and ionic salts (oxidants). Two chemical oxidants widely used in PPy synthesis - ferric chloride and ferric tosylate - were compared. Upon exposure to pyrrole vapor, both oxidants produced PPy conducting polymers over PS nanofibers. The ferric tosylate containing template fibers showed much faster PPy growth kinetics than the ferric chloride containing fibers. The PPy growth on ferric tosylate containing template fibers produced highly faceted fibers and gave a higher degree of crystallization of PPy than the PPy grown with ferric chloride containing templates. The intrinsic doping of PPy was slightly higher in the PPy layers grown with ferric tosylate. The combination of higher degrees of crystallization and doping resulted in a higher conductivity for PS-PPy nanofiber mats produced with ferric tosylate than those produced with ferric chloride.