Research Areas

Our interests focus on the relationships between hierarchical structure and mechanical function of polymeric materials.  Hierarchical structure in biocomposite systems such as in collagenous connective tissue has many scales or levels, and there are highly specific interactions between these levels. We were among the first to demonstrate that the hierarchical architecture is designed to accommodate a complex spectrum of mechanical property requirements. The hierarchical structure-property relationships have been described in several soft connective tissues: tendon, intestine and invertebral disc.  Numerous levels of organization are found with highly specific interconnectivity and unique architectures designed to give the required spectrum of properties for each oriented composite system. From these lessons in biology, the laws of complex composite systems for functional macromolecular assemblies are considered.

The other area of interest focuses on exploring the structure-processing-property relationships in polymeric materials. Pioneering contributions have been made in understanding the connections between hierarchical structure and irreversible deformation and damage processes, and fracture of polymer blends and composites. New insights have been developed into mechanisms of compatibilisation and toughening of polymer blends. We have pioneered in the development of effective industry/academic research cooperation. As an example, with Dr. S. P. Chum of The Dow Chemical Company, a unique and comprehensive study of the structure-property relationships of metallocene-catalysed ethylene-octene copolymers was carried out, which has led to a definitive theoretical understanding of the connections between microstructure, morphology and mechanical properties. This work has, in turn, produced predictive models which have assisted the development of a new commercially-successful family of ethylene-based elastomers. Motivated by the need for new processing technologies for creating engineered microstructures of incompatible polymers, ground-breaking studies have been undertaken to explore the unique advantages that can be achieved with microlayering coextrusion. This layer-multiplying technology permits continuous processing of sheet or film with hundreds or thousands of alternating layers of two or more polymers. With this technology, we have created engineered microstructures with unique electrical, mechanical and barrier properties. With E. Baer, the hierarchical structure-function relationships in collagenous tissues have been explored. Numerous levels of organization are found with highly specific interconnectivity designed to produce the particular spectrum of properties for each oriented composite system. A further area of interest with J. M. Anderson is in understanding mechanisms of biocompatibility and biodegradation of biomaterials with a view to enhancing their biostability.