Using redox active molecules to build multilayered architecture on carbon fibers and the effect on adhesion in epoxy composites

Carbon fibres with redox-active surface functionalities have shown potential applications in environmental remediation, and as burgeoning materials for structural batteries and super capacitors. In this work we describe the tethering of anthraquinone, capable of a reversible 2 electron transfer in aqueous medium, to the carbon fibre surface, and the corresponding effect on interfacial adhesion. The anthraquinone alone results in a >150% improvement in interfacial shear strength and the redox activity is preserved. Further to this, we then use this conductive film as a means to grow an acrylic acid polymer on top of the anthraquinone base layer, characterised by water contact angle, infrared spectroscopy, and depth-profiling X-ray photoelectron spectroscopy. This outermost layer imparts additional benefit to fibre-to-matrix adhesion and preserves the redox activity of the modified carbon fibers. This work demonstrates the ability to grow dual component and covalently-attached sizings to the carbon fiber surface, without compromising the inherent benefits of the underlying carbon fibers.