8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P8.26Thu 811:10-14:00Structure and dynamics of depletion-inducedprotein-polymer gelsNajet Mahmoudi, 1 Peter Schurtenberger, 2 and Anna Stradner 21 BSS, Cavendish Laboratory, 19, J J Thomson Avenue, CB3 0HE, Cambridge,United Kingdom2 Physical Chemistry, Department of Chemistry, Lund University, Lund, SwedenWe have investigated the phase behaviour of weakly charged protein / polymer mixtures using caseins,which are electrosterically-stabilized self-assembled structures of milk proteins of 200 nmsize, and a low molecular weight (polyethylene oxide). The combination of visual observations,diffusing wave spectroscopy, and confocal microscopy allowed mapping out a state diagram ofaqueous casein / PEO mixtures under different solvent conditions. In high ionic strength conditions,where the electrostatic interactions due to residual charges are sufficiently screened, weobserve the classical sequence of phases/states ranging from a fluid one-phase region via a twophaseregion up to a region where we observe dynamical arrest. Casein-polymer gels have beenshown to stiffen with time, as demonstrated by diffusive wave spectroscopy and rheology, howeverconfocal microscopy indicates that there are no large-scale structural changes. Nevertheless, thegels collapse within several days to weeks. A particularly interesting observation was made at lowionic strength: in these systems, where we have a mixed potential, clusters form, while neitherfluid-fluid phase separation nor gelation could be observed in any of the samples investigated.26