Materials World Network: Composite Single Crystals - From Structural Evolution to Mechanical Characterization

The combination of synthetic materials science with design concepts adapted from Nature is a promising route to the development of new materials. Biominerals such as bones, teeth and seashells provide an ideal inspiration for this approach, as illustrated by Nature's ability to manipulate mechanically weak engineering materials such as calcium carbonate to produce hard skeletal materials that exhibit excellent fracture toughness and unique morphologies. One key feature of these composite materials, which is an essential feature of their superior mechanical properties, is their structures involve strong intercalation of organic molecules within the mineral host. Here organics can not only be located between crystalline units as for materials such as nacre, but also within single crystals, as found for example in sea urchin spines. Indeed, single crystal biominerals often occlude up to several weight per cent of macromolecules, which is perhaps surprising given that crystallization is traditionally considered to be a method for purifying solids.

We will investigate the application of this biogenic strategy - the encapsulation of "inclusion materials" within single crystals - to create novel composite materials. Although the potential for synthesizing composite materials based on this approach is enormous, our lack of fundamental understanding means that progress in this field remains largely based on trial-and-error experiments. In this project, we have assembled an international team of researchers uniquely positioned to fill this gap, and by doing so we will develop a comprehensive understanding of 1) the mechanisms by which "inclusion materials" are occluded within a crystal lattice; 2) the internal micro- and nano-structure of the resulting single crystal composites; and 3) how the resulting structures ultimately dictate the mechanical properties of the resulting composite material. Our research strategy is based on a systematic study of the incorporation of a broad range of "inclusion" materials - ranging from molecules to microscopic polymer particles, and from compliant to stiff frameworks. We will design and synthesise bespoke molecules, particles and gels with appropriate chemical structures to promote intercalation, and in doing so develop the first truly unified understanding of how additives are occluded within crystals. It is also expected that novel syntheses of polymeric particles and gels will also result from this approach.

Understanding the strategies by which biominerals form, and how their design leads to superior properties is clearly a complex, multidisciplinary problem, encompassing fields such as crystal growth, materials characterisation, polymer chemistry, and analysis of mechanical properties. This joint NSF-EPSRC research grant involves an international collaboration between a consortium of world-leading research groups based in the USA and the UK, who by working closely together seek to combine the multidisciplinary expertise of each team to address this complex scientific problem and hence enable the rational design of novel biomaterials. Our ultimate goal is to create for the first time a truly unified understanding of how additives - ranging from molecular, to polymeric, to particulate, to compliant and ultimately stiff frameworks - can be incorporated within single crystals, and to determine how this strategy can be applied to the design of new materials with specific mechanical properties. This integrated approach will provide a general methodology for synthesizing composite crystals, contribute to our understanding of the biological systems from which the inspiration came, and will ultimately provide the basis for synthesizing next-generation materials such as artificial bone and tough synthetic dental enamel.

Prof. Armes has worked extensively with many industrial companies, ranging from the world's largest chemical company (BASF) to a single employee SME. Current sponsors include: DSM, P & G, BP, Cytec, Biocompatibles, Reckitt Benckiser, Cabot Plastics, Scott Bader and Vivacta. He sold a U. Sheffield patent application to DSM for 125,000 euros in Sept 2007. This technology is now the basis of a successful anti-reflective coatings business for DSM, which captured 30 % of the global market for high-quality picture glass for fine art within six months of the launch of its first product (ClarylTM; see www.dsm.com). DSM now describes its interaction with Prof. Armes as an exemplar of its recently adopted 'open innovation' policy, which aims to acquire externally-owned IP of potential strategic value. Thus Prof. Armes is well aware of the value of IP protection (he is a named inventor on 16 patent applications) and is undoubtedly 'outward-facing' regarding the potential commercial impact of his work. Moreover, he has recently filed two new U. Sheffield patent applications arising from his joint EPSRC research programme with Prof. Meldrum which underpins the design and synthesis of the diblock copolymer 'nano-objects' described in the present grant application. He has already exploited this strong IP position to leverage £46 K from Scott Bader and £235 K from DSM for industrially-relevant follow-on projects. Prof Meldrum has previously worked with a number of industrial partners, including Nexia Solutions, Unilever (Vlaardingen, the Netherlands and Colworth, UK) and Procter and Gamble. Both Unilever sites funded PhD studentships, as did Nexia Solutions, while technical discussions are ongoing with P&G. She has also recently carried out consultancy work with BP on the topic of the nucleation and growth of gas hydrate compounds.

In 2005 the University of Sheffield sold its entire IP rights to Fusion IP in a ten-year pipeline deal worth £10 M. This AIM-listed company has first refusal to commercialise inventions by University employees arising from Research Council contracts. Prof. Armes is currently negotiating with Fusion IP over the possible formation of a spin-out company to exploit his two new patent applications on the synthesis of diblock copolymer 'nano-objects', which also underpin his scientific contribution to this NSF-EPSRC grant proposal. Alternatively, if a spin-out company is not considered the best business option, Fusion IP can provide appropriate business expertise to aid the negotiation of individual patent licences or outright patent sales. Finally, the Sheffield Polymer Centre (directed by Prof. Armes and managed by Dr. L. R. Sutton) is also a useful vehicle for fielding company-led enquiries for IP generated by U. Sheffield polymer scientists. We have a database of more than 1,000 companies and regularly interact with a wide range of corporate clients. This activity has led to both Beiersdorf and Agilent purchasing samples of Prof. Armes's diblock copolymers for evaluation in specific in-house applications. Thus we have the capacity and infra-structure to respond effectively to external enquiries from third parties. The University of Leeds has a similar pipeline deal with IP Group, which is a privately owned company that has the first right of refusal on the IP generated by both Leeds and nine other UK Universities. The Enterprise and Innovation Office at Leeds University has recently undergone restructuring with a view to streamlining their commercial activities, and has already led to the creation of 47 University spin-out companies including Tracsis, a software company which services global transportation industries, and Chamelic, which manufactures advanced surface coatings based on stimulus-responsive polymers.