A leading expert in a branch of polymer chemistry visited TWI in October to deliver a fascinating talk on polymer-graphene composites.
The invitation to Peter Budd, Professor of Polymer Chemistry at the University of Manchester, was linked with a TWI-partnered PhD programme now underway to develop and assess PA11-graphene composites and coatings and optimise their use for oil and gas applications.
Prof Budd, along with colleagues Prof Ian Kinloch and Dr Oana Istrate, was welcomed to the organisation's Cambridge headquarters by Dr Paul Woollin, TWI Research Director. They were joined by Thomas Raine, student of the University, who has recently begun his PhD in conjunction with TWI, focusing on polymer-graphene composites with improved barrier performance.
The results of Thomas's PhD will be made available for the exclusive benefit of TWI Industrial Members.
In the introduction to his talk, Prof Budd revealed that anyone can prepare graphene with a thickness of tens of nanometres, simply by scribing a pencil across paper or using sticky tape to cleave off layers from graphite. Prof Budd then explained that the 2010 Nobel Prize in Physics had been awarded to Sir Andre Geim and Sir Kostya Novoselov of the University of Manchester for their analysis of graphene's properties, which are indeed impressive. Of notable interest is the 20% elasticity of this single-atomic-layer material, coupled with its impermeability to the smallest molecules, such as helium. Methods for preparation of graphene include solution exfoliation from graphite and the preparation of large sheets through chemical vapour deposition.
Throughout the presentation, Prof Budd referred to relevant research from the University of Manchester and other academic institutions. Graphene and its derivatives have potential applications as ionic conductors, sensors, molecular separation membranes and barrier materials.
In fact, both the opportunity for surface modification and the inherent properties of graphene make it a welcome addition to the area of membrane or barrier research. Membranes are designed to be selectively permeable to one species over another, making them useful in processes from particle filtration to vapour permeation and gas separation.
Prof Budd went on to describe that it is possible to functionalise the graphene surface to the hydrogenated, fluoride or oxide form, thus ensuring increased compatibility with a matrix polymer or facilitating chemical reactions with other moieties.
The selectivity of the graphene complex alters with surface chemistry. Whereas graphene is essentially impermeable to water vapour and helium, a graphene oxide film allows water vapour through. Prof Budd provided examples showing increased selection of hydrogen over carbon dioxide when a graphene oxide film with thickness in the range of 1.8-18nm was present. Other researchers had examined the molecular sieving of organic and inorganic complexes with hydrodynamic radii of the order of 3-6 . Another study described the shutdown of the transport of water by the reduction of graphene oxide to form self-supporting films.
Prof Budd also introduced the concept of organic polymers of intrinsic microporosity in the form of PIM-1. PIM-1 has a contorted structure containing permanent voids, resulting in a material that is selectively permeable to oxygen over nitrogen. The permeability can be altered further by the incorporation of graphene into the PIM-1 matrix. After thermal treatment to carbonise PIM-1, the selectivity for carbon dioxide over methane was evident. Prof Budd identified extreme thermal treatment as being an interesting avenue currently being researched, which could potentially lead to a graphene replacement being prepared from plastic.
In summary, Prof Budd provided an interesting overview to a diverse audience on the potential for selectivity using graphene-based complexes. The presentation culminated in a question and answer session, which was supported further by Prof Kinloch.
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