Electrografting of thiophene, carbazole, pyrrole and their copolymers onto carbon fibers: electrokinetic measurements, surface composition and morphology

Abstract

In order to improve the surface properties of carbon fiber without affecting the mechanical properties of the reinforcing fibers, various monomers (pyrrole (Py), carbazole (Cz) and thiophene (Th)) were used to electrograft conjugated copolymers. The electrocoated carbon fibers were characterized with respect to their surface morphology and surface composition, using scanning electron microscopy (SEM) and FTIR-reflectance spectroscopy, respectively. In general very homogeneous and continuous coated carbon fiber surfaces were obtained. The pH-dependent zeta ( ζ)-potential measurements were applied to characterize the surface properties of all electrocoated fibers. The performed ζ-potential measurements reflect that the surface state is strongly dependent not only on the composition of the grafted polymers (different homopolymers, copolymers and a single terpolymer), but also on the extent of doping by the counter ion from the supporting electrolyte. Polymers or copolymers formed in solution during the electrografting process were also analyzed using FTIR-reflectance, 1 H NMR and UV–VIS spectroscopy, as well by gel permeation chromatography (GPC) and elemental analysis. Such a detailed investigation of well known electrografted copolymers opens the possibility to use such ‘superior’ materials in the field of carbon fiber reinforced polymeric composite materials. The main advantages of such homogeneous and dense electrocoatings are their thermal stability and the fact that one can design the surface composition and morphology.