Quantitative analysis of native reactive functional groups on carbon fiber surface: An electrochemical approach

Abstract

Quantitative insight into the distribution of different reactive functional groups on carbon fiber surfaces is essential for designing surface modification strategies and tailoring matrix-fiber interactions. In order to determine the amount of –OH, –COOH and –NH2 functionalities on carbon fiber surface, we covalently bound ferrocene structures to these moieties via a set of reactions including acylation, ester coupling and Schiff base formation. Following cyclic voltammetry experiments using the functionalized fibers as working electrodes, the amount of ferrocene structures could be conveniently calculated and the reactive functionalities quantitatively determined in knowledge of their distinct reactivity profile. The electrochemical experiments and proceeding of the corresponding reactions were further substantiated by analyzing the high-resolution C1s, O1s and Fe2p X-ray photoelectron spectra. It appears that the amount of reactive functional groups are quite high (~1.8 × 1014 molecules cm−2), and these functionalities consist mainly of –OH groups (~97%). The amount of surficial –NH2 (~2.7%) and –COOH (~0.3%) groups is rather low. Our study might open up new avenues towards novel functionalization strategies targeting –OH groups, and the electrochemical method can provide new insights into the functional group profile when carbon fiber surface is oxidized, as we show on a case study.