Valeria Arrighi BSc, PhD, DIC, CChem, FRSC

Profile

• Third Year Study Director
• Deputy head of Materials Chemistry research grouping
• Strategic Funding Group

 Properties of Polymers

Over a number of years, our group has investigated various aspects of physical behaviour from conformation and orientational order, to local structure and dynamics, in a wide range of polymeric materials. Current interests include studies of the miscibility and physical ageing in polymer blends as well as investigations of the mechanical and dynamic properties of nanocomposites. We are also synthesising a range of polyurethane structures aiming to incorporate interesting optical and liquid crystalline properties.

1. Polymer Blends and Nanocomposites

Our work on polymer blends focuses on systems with strong, specific interactions between the blend components (hydrogen bonding). Very few physical ageing studies dealing with polymer blends have been reported in the literature and to date no clear understanding of the relationship between ageing in blends and pure components has been achieved. By altering the chemical structure of one of the polymers or through copolymerisation, we are varying the strength of the interactions and monitoring ageing by using enthalpy relaxation and FTIR. One further area of current interest is nanocomposites. We are incorporating silica nanoparticles into polymer matrices using different methods, including grafting from the surface of the nanoparticle. Our aim is to compare the mechanical, dynamic and ageing behaviour of the different systems with a view to optimise performance.

Figure 1. Effect of temperature on hydrogen bonding interactions in polyethylene oxide) /poly(hydroxy styrene) (PEO/PHS) blends - FTIR data.

2. Polymer Dynamics

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.

1. 'Fast and Slow Dynamics of Isotactic Polypropylene Melts', J. Tanchawanich, V. Arrighi, M.C. Sacchi, M.T.F. Telling and A. Triolo, Macromolecules, 2008, 41, 1560.
2. 'Towards a Universal Approach to Enable Transfer of Equilibrium Constants in Hydrogen Bonded Blends', S. Shenoy, V. Arrighi and J.M.G. Cowie, Macromolecules, 2008, 41, 3769.
3. 'Temperature Dependence of the Primary Relaxation in 1-Hexyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide', O. Russina, M. Beiner, C. Pappas, M. Russina, V. Arrighi, T. Unruh, C.L. Mullan, C. Hardacre, and A. Triolo, J. Phys. Chem. B, 2009, 113, 8469.
4. 'Physical ageing', J.M.G. Cowie and V. Arrighi, in Polymer Physics – from Suspensions to Nanocomposites and Beyond, L.A. Utracki, A.M. Jamieson (eds.), Chapter 9, Wiley (2010).