SILGRAFUN · Multifunctional graphene/silicone nacre-like composite films

Multifunctional graphene/silicone nacre-like composite films

Lightweight, conductive and mechanically robust composites are key for the development of a variety of hi-tech industries of high socio-economic relevance. When processing such composites, nanoscale events govern the bulk properties and some continue to be not fully understood. This has delayed the industrial uptake of nanocarbons in the composite industry and the fulfilment of the scientific expectation of conferring extraordinary properties to polymers at low filler content. In the case of graphene, it has been found that this transference of properties is mostly limited to the number of layers found in the original graphenic derivative. Unfortunately, predominantly monolayer graphene in high quality and large quantity is still an infrequent product. Additionally, due to its inertness, pristine graphene results incompatible with most solvents and polymers. This entails functionalisations or modifications that are not easily pushed to completion prior to compositing and can hamper the electrical conductivity of the pristine sp2 carbon lattice. Graphene oxide (GO) in contrast, although less conductive when reduced and having limited solubility in organic solvents, is mass-producible. Its oxygen-containing functional groups enable access to high aspect ratio water-based suspensions with monolayer contents above 95%, both crucial characteristics to account for high quality composite production. In this context, SILGRAFUN´s objectives have been to develop a novel strategy for processing both graphene and GO composite films and address their study as multifunctional materials for applications such as anticorrosive coatings, strain sensors or high-K materials. Using polymers containing pyrene- and NH2-dangling units, we have aimed to stabilise graphene and GO, respectively, in organic solvents and polydimethylsiloxane (PDMS)-based polymers. We propose a system in which the polymeric functionalisation that is created on the surface of GO can be opportunely removed: polymer brushes that enable dispersing GO in an organic PDMS matrix can be cleaved through UV-light once their dispersing function has been exploited. Since bulk conductivity and mechanical reinforcement change from the original functionalised state to the photo-cleaved one, in this study we provide an insight into how the nature of the graphene or rGO-interface alters morphologies, and in turn the inter-particle distance, of graphene or rGO/PDMS composites. We believe our study could have a great impact on a new generation of smart graphene-based composites with highly targeted final properties.

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