Centre for Water Soluble Polymers

The Centre, in collaboration with groups at University Wales Bangor, has been awarded the status ‘Centre of Excellence for Technology and Industrial Collaboration’ (CETIC) in a programme funded by the Welsh Funding Council, The Welsh Development Agency and The National Assembly of Wales. The Centre receives funding from a variety of sources including UK Government, EPSRC and EU and has extensive links with Industry.

The main research focus has been concerned with the synthesis, characterisation, properties and applications of a broad range of natural and synthetic water soluble polymers.

Chemical characterisation. We have made considerable advances in determining the molecular structure of the complex polysaccharide, gum arabic by developing procedures to fractionate the gum (ion exchange and hydrophobic affinity chromatography) and by performing alkaline and enzyme hydrolysis studies. We have isolated and characterized a specific arabinogalactan-protein fraction responsible for the gum's emulsification properties. A similar approach has more recently been applied to sugar beet pectin which also shows potential as an food emulsifier.

Physicochemical characterisation. Studies have included the determination of the hydrodynamic size, molecular mass and molecular mass distribution of polymers using dynamic light scattering and gel permeation chromatography coupled with various detectors (multiangle laser light scattering, photon correlation spectroscopy, refractive index and UV absorbance) to gain information about the size and shape of macromolecules. A recent project has involved the development of a new integrated flow field flow fractionation multiangle laser light scattering system to determine the molecular mass distribution of very high molecular mass biopolymers and synthetic flocculants.

Properties of polymer solutions. Novel associative thickeners have been synthesised and their shear flow and viscoelastic behaviour and interactions with surfactants determined. Significant progress has been made in the measurement and modelling of the extensional flow properties of a variety of polymer systems. Polymer conformation (polysaccharide coil-helix transitions) and gelation mechanisms have been studied using the ESR nitroxide spin label/spin probe technique and differential scanning calorimetry. This has also enabled significant progress to be made in understanding the nature of the interactions in mixed polysaccharide systems and the development of novel gel structures.

Adsorption of polymers at surfaces. Studies have been undertaken on a wide range of polymers and substrates. Work has mainly involved determination of adsorption isotherms and the use of ESR spectroscopy, photon correlation spectroscopy and fluorescence techniques to monitor the configuration of polymers adsorbed at the solid-liquid interface and to study polymer/polymer and polymer/surfactant competition. Particular emphasis has been paid to the effect of adsorbed layer characteristics on the stability and rheological properties of concentrated suspensions. Significant advances have been made in the understanding of polyelectrolyte adsorption. Recent work has involved the development of novel food emulsifiers based on polysaccharide-protein complexes.

Phase behaviour in polymer/polymer, polymer/particle and polymer/surfactant mixtures. Work has involved an experimental investigation of the flocculation of particles by non-adsorbed polymer and the phase behaviour of mixed systems. Phase separation and colloid aggregation have been explained on a theoretical basis by polymer depletion theories. It has been demonstrated that liquid –liquid phase separation can be used to separate proteins from mixtures. Studies have also been undertaken to investigate how phase separation processes can be exploited in order to produce novel gel structures for food and other applications.

Professor Williams Recent Publications