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

Wed 711:10-14:00P5.23Charged colloid-polymer binary mixtures: competitionbetween electrostatic and depletion interactionsJose Callejas-Fernandez, 1 Miguel Pelaez-Fernandez, 1 Arturo Moncho-Jorda, 2Sonia García-Jimeno, 3 and Joan Estelrich 31 Universidad de Granada, C/Fuentenueva s/n. Facultad de Ciencias, 18071, Granada,Spain2 University of Granada, Granada, Spain3 Universidad de Barcelona, Barcelona, SpainWe report a study on binary mixtures formed by charged colloids (liposomes) and slightly chargedpolyacrylamide polymers (PAM) of different molecular weight. The main aim is to highlight,experimentally, a noticeable competition between long-ranged repulsive electrostatic interactionsand short-ranged attractive depletion interactions. For this task, colloidal fluids (like Wigner glassat high particle volume fraction) stabilized by electrostatic repulsion are firstly formed and then,increasing amounts of PAM polymers are added. The colloidal structure and the dynamic ofliposomes are analyzed using Static and Dynamic Light Scattering techniques. The experimentaldevice is a 3D-DLS apparatus. The shift of S(q)s peaks to high q values clearly show that thedepletion forces counteract the repulsive electrostatic forces between colloids. Also, the shapeof the dynamic structure factor of the liposomes, f(q, t), that without added polymer resemblethe corresponding to ”arrested particles”, becomes strongly modified by the presence of polymer.We conclude that the initial ”cages”, formed by electrostatic repulsion forces between chargedliposomes, are broken by the presence of the PAM molecules.Acknowledgments: The authors are grateful to MCINN (Project No. MAT2009-13155-C04-02),ERDF Funds and Junta de Andalucía (Excellency Project P07-FQM-02517 and P07-FQM-02496)for financial support. References.[1] A. I. Campbell, V. J. Anderson, J. S. van Duijneveldt, and P. Bartlett, Phys. Rev. Lett.94, 208301(2005).[2] M. Peláez-Fernández, A. Moncho-Jordá, and J. Callejas-Fernández, Europhys. Lett. 90, 46005(2010).ext[3] C. L. Klix, C. P. Royall and H. Tanaka, Phys. Rev. Lett. 104, 165702 (2010).23