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Adsorption and Complexation of Nano-colloids with Gels

Eloise Stattersfield

Eloise Stattersfield (previous student, left the group in 2003)

Macromolecules are widely used to modify the properties of colloidal systems. Polymers are adsorbed on the surfaces of colloidal particles to alter properties such as rheology and stability. Polymer adsorption onto surfaces is therefore an extensively studied subject. Until recently these studies have primarily focused on polymers adsorbed on flat surfaces or on polymers adsorbed on particles which are much larger than polymer. This project sets out to investigate the case where the colloidal particle is much smaller than the adsorbed polymer. The subject has yet to be widely explored, but applications in water purification, paper production and the role of such systems in biological applications has lead to growing interest in the field. Theoretical predictions were made about the interactions between small colloidal particles and larger adsorbed polymers by Alexander1 and Marques and Joanny2. In 1990 Lafuma, Wong and Cabane3 set out to investigate whether or not the analysis and concepts, which had been developed for polymers, adsorbed on macroscopic surfaces still held for polymers adsorbed on small colloidal particles. They found in this and subsequent work that the small particle will only occupy a part of the polymer chain, leaving space for other particles to adsorb. Further particles lead to formation of macroscopic aggregates or finer structures, such as necklaces of particles on polymer chains. The structures formed are very diverse and depend on the number concentration of the particles, adsorption affinity, inter-particle interactions and the structure of the polymer molecules. 4-12

This project will use rheology, NMR, PCS and neutron scattering to obtain a detailed picture of the interaction between high molecular weight polymers and small colloidal particles. The project will initially make use of systems of well characterised polymers and particles, in order to assemble a clear picture of the mechanisms involved. It will then investigate more complex polymer and particle systems. The aim of the work is to develop a model, which will allow the behaviour of systems of high molecular weight polymers and small colloidal particles to be predicted. One possibility will be to use the particle as a pseudo solvent for the polymer and investigate interaction energies.

Experimental work has found that there is a maximum number of silica particles which may be added to a polymer system before aggregation will occur. This point is characterised by a maximum in the zero shear viscosity of the system, and increases with decreasing particle diameter. Before this point is reached the system is shear thinning in character and after this point the system becomes shear thickening.

NMR results suggest that two different structural regimes may exist These may be one where the PEO is adsorbed around the silica particle and the other where the silica becomes part of the polymer matrix.

These structures will be investigated using Neutron Scattering.

Further Reading

  1. Alexander, S., J. Phys (France) 38, 1977, 977
  2. Marques, C.M., Joanny, J.F., J.Phys (France), 49, 1988, 1103
  3. Lafuma, F., Wong, K., Cabane, B., J.Colloid and Interface Sci., 143, no.1, 1991
  4. Cabane, B., Wong, K., Wang, T.K., Lafuma, F., Duplessix, R., Colloid and Polymer Science, 266 1988, 101-104
  5. Wong, K., Lixon, P., Lafuma, F., Linder, P., Aguerre Charriol, O., Cabane, B., J.Colloid and Interface Sci., 153, no.1, 1992, 55
  6. Spalla, O., Cabane, B., Colloid and Polymer Science, 271, 1993, 357-371
  7. Liu, S.F., Legrand, V., Gourmand, M., Lafuma, F., Audebert, R., Colloid and Surfaces A, 111, 1996, 139-145
  8. Spalla, O., Nabaui, M., Minter, J., Cabane, B., Colloid and Polymer Science, 274, 1996, 555-567
  9. Cabane, B., Wong, K., Linder, P., Lafuma, F., Journal of Rheology, 41(3), 1997, 531
  10. Nowicki, W., Nowicka, G., Colloid and Polymer Science, 273, 1995, 473-479
  11. Furusawa, K., Shou, Z., Nagahashi, N., Colloid and Polymer Science, 270, 1992, 212-218
  12. Liu, S.F., Lafuma, F., Audebert, R., Colloid and Polymer Science, 272, 1994, 196-203

This project is funded by University of Bristol and Kodak Ltd