Properties of Polymers
Our research focuses on understanding structure-property relationships in polymeric materials, including thermal, mechanical and dynamic behaviour in polymer-polymer mixtures, liquid crystalline polymers, composites and nanocomposites.
Our main area of expertise is in the application of scattering techniques to investigate structure and dynamics of polymers.
1. Polymer Blends and Nanocomposites
In collaboration with Dr Arno Kraft, we have prepared a series of novel nanocomposites using techniques such as such as atom-transfer radical polymerisations (ATRP). Our work in this area aims to understand how covalently bonding chains onto nanoparticles alters their macroscopic properties (ageing, thermal and mechanical) to microscopic behaviour (both structure and molecular dynamics) with a view to optimise performance. Despite the practical importance of polymer-polymer mixtures, very few physical ageing studies of blends have been carried out and there is no clear understanding of the relationship between ageing in blends and pure components. Our work on blends focuses on ageing studies using enthalpy relaxation on systems with strong, specific interactions between the blend components (hydrogen bonding).
Figure 1. Dispersing and grafting PMMA chains on silica nanoparticles enhances mechanical properties. Grafting has the greatest effect.
While the individual repeat units of a polymer chain are chemically simple, their connectivity introduces a complex structural and dynamic behaviour. Understanding polymer motion is a great challenge. Most of the work carried out in our group makes use of quasielastic neutron scattering (QENS), a technique which gives information on high frequency motions taking place on a local scale. The goal of this work is to improve our understanding of mechanical and flow properties in polymers as well as polymer blends and nanocomposites. Systems that are currently under study are blends interacting via hydrogen bonding and the polymer grafted silica nanoparticles prepared in our laboratory.
Figure 2. Natural and synthetic polymers display a range of dynamic processes which can be studied by neutron scattering.
3. Synthesis and Properties of Polyurethanes
Polyurethanes (PUs) are a versatile class of polymers, with wide ranging applications from seals and elastomers (e.g. Spandex) to high performance adhesives and coatings. Given the wide choice of starting compounds (e.g. long chain diols, aromatic or aliphatic diisocyanates), the end properties of the polyurethanes can be easily tailored by varying the chemical structure as well as the ratio of reactants. Using a prepolymer synthetic route (i.e. end capping long chain diols with diisocyanates followed by addition of a chain extender), we are preparing PUs incorporating mesogens and lactic acid oligomers, aiming to generate materials with enhanced mechanical and/or optical properties.
Figure 3. Prepolymer synthetic route for polyurethanes.