Kevin Mutch

Prof. Julian Eastoe

Colloid-Polymer Mixtures in the Protein Limit.

Kevin completed his undergraduate degree in chemical physics at The University of Edinburgh. He is carrying out his PhD jointly supervised by Julian Eastoe and Jeroen van Duijneveldt in the area of colloid-polymer mixtures in the protein limit.

Colloid-polymer (CP) mixtures have been studied extensively in the last fifty years though mostly in the colloid limit. Asakura and Oosawa [1] published some important results in the 1950’s which suggested a depletion interaction exists in colloidal solutions with added non-adsorbing polymer when the polymer is significantly smaller than the colloid. This is known as the ‘Colloid Limit’ wherein the size ratio, q, of the colloid to polymer is smaller than 1 --- q = 2R_g/s<1 where σ is the colloid diameter and R_g is the polymer radius of gyration. The ‘Protein Limit’ is the case where the polymer is larger than the colloid and this case has been studied much less.

Most of the work carried out in the protein limit thus far has concerned the phase behaviour of such systems [2]. This project aims to extend this to a study of the structure of the CP mixtures using small angle neutron scattering (SANS) and through this, study the effects of changing system parameters such as the solvent quality. Some recent work has demonstrated the applicability of SANS to such studies in the protein limit, using different model colloids [3].

Unlike these systems, which have adopted for example acrylate based colloids, this project will use microemulsions, which are very easy to make. By exploiting the phase diagram, it is also possible to make different sized droplets and due to the small size of microemulsion droplets (typically 5-50nm), large values of q would be accessible.

This work is sponsored by EPSRC and is jointly supervised by Julian Eastoe and Jeroen van Duijneveldt.

[1] J. Chem. Phys, 1954, 22, 1255; J. Polym. Sci., 1958, 33, 183.

[2] Z. Zhang and J. S. van Duijneveldt, Langmuir, 2005, ASAP.

[3] J. Colloid Interface Sci., 2004, 279(2), 447; J. Chem. Phys, 2005, 123(1), 014903; Macromolecules, 2005, 38(1), 151; Macromolecules, 2005, 38, 9783.