Role of Surfactants in the Synthesis of Poly(p-phenylene) Film in Microemulsions

Abstract

Poly(p-phenylene) (PPP), electrosynthesized in different microemulsions by the oxidation of benzene in the form of a uniform and adherent film on Pt surfaces is characterized with a view to understanding the role of different types (anionic, nonionic, cationic) of surfactants. The scanning electron microscopy results reveal distinct morphological changes in the films synthesized with cationic, nonionic, and anionic surfactant systems. The evidence from X-ray photoelectron spectroscopy investigations indicates the incorporation of the sulfur species in the film for the case of cationic surfactant while the anionic and nonionic surfactant systems do not show a sulfur signal. IR investigations of the polymer films show a small degree of cross-linked structure with a long backbone containing aromatic rings irrespective of the surfactant whereas 13C cross polarization magic angle spinning NMR (solid state) data support the 1,4 substitution (linkage) in the monomer unit in PPP. Differential thermal analysis/thermalgravimetric analysis indicates a higher thermal stability of PPP due to a longer polymer backbone deposited from the anionic surfactant system. The cyclic voltamograms of the films indicate a progressive change in the redox behavior, which correlates well with the relative stability of the intermediate species with a change in surfactant system.