Design of polymer-clay nanocomposites via control of phase behaviour

Polymer-clay nano-composites, formed by dispersing suitably modified clay within polymer, are known to exhibit enhanced properties, such as gas impermeability and flame retardance, relative to un-modified polymer. Consequently, these materials have found application in food and drink packaging and construction. However, these materials could potentially have much wider application considering the range of plastic products in use today (e.g. plastic films, membranes and components), and their use in biomedical, pharmaceutical and display technology industries is envisaged. However, current understanding of how these materials can be tailored for particular applications is severely lacking. The problem here is two-fold. Primarily, there is little understanding of how dispersion of clay in these materials can be controlled to achieve a particular morphology or phase. Consequently, there is a lack of understanding about how the phase behaviour of dispersed clay impacts on material properties. Solving these problems will have a dramatic impact on our ability to design and process composite materials for specific applications, and could also reveal additional characteristics that are important in completely novel applications.The primary aim of the work in this proposal is to address the first issue. That is, we wish to understand how these materials can be produced with specific phase morphologies. A secondary aim is to characterise material properties for a range of polymer-clay nano-composites. To achieve our first aim we have devised a novel manufacture technique that should allow straightforward control over the morphology of the final composite materials. This technique has two stages; the first involves control of the phase behaviour of precursor materials, while the second involves 'locking-in' this morphology as the precursor material is transformed into the final composite material. Our precursor materials consist of clay platelets dispersed in a monomer solvent, possibly with added polymer. So the first stage of our proposal is focussed on understanding the complex phase behaviour of these precursor materials. The second stage involves fast 'in-situ polymerisation' to transform the monomer solvent in our precursors completely into polymer - thereby fixing the precursor morphology within the final composite material. So the second stage of our proposal is focussed on understanding this 'fixing' process. Finally, we will analyse the materials produced in terms of their physical properties.The proposed project involves a coordinated program of theory and experiment aimed at gaining fundamental understanding of the physical chemistry (phase behaviour of precursors, kinetics of in-situ polymerisation, and physical properties) of these advanced materials. Moreover, knowledge and expertise generated by this study will have relevance for other materials consisting of disk-like nano-particles immersed in (possibly polymeric) solvent.