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

P5.148Wed 711:10-14:00Polyelectrolyte-induced aggregation of liposomes:charge patch attraction and cluster phase formationSimona Sennato, 1 Domenico Truzzolillo, 2 and Federico Bordi 11 Dipartimento di Fisica La Sapienza Università di Roma, Piazzale Aldo Moro 2, 00185,Roma, Italy2 Institute of Electronic Structure and Laser, Foundation for Research and Technology,Heraklion, GreeceSelf-assembly of charged liposomal particles with oppositely charged polyions gives rise tofinite-size aggregates, a new ”cluster phase” whose intriguing properties are not yet completelyunderstood. Close to the isoelectric point, vesicles form large aggregates, whose size can beappropriately tuned by varying the concentration ratio, and reaches its maximum at the isoelectriccondition (re-entrant condensation) where charge inversion occurs [1, 2]. Apparently, theformation of the observed kinetically stabilized cluster phase results from some balance betweenlong-range electrostatic repulsion and short-range attraction. On the basis of past investigations onthe re-entrant condensation behavior, we proposed that the aggregation mechanism is connected tothe strong local correlation between polyelectrolyte chains adsorbed on the liposomes’ surface andconsequently to the non uniformity of the charge distribution on the ”polyelectrolyte-decorated”liposomes [2]. Modelling the inter-particle interactions by means of the Velegol and Thwar potential,that describes the effect of a non-uniform surface charge distribution of the particles [3], weexplored by Monte Carlo simulations the aggregation kinetics of polyelectrolyte-decorated colloidsystems and reproduced semi-quantitatively the main features of the re-entrant condensation [4].The observed destabilizing effect of added salt, that manifests itself as an abrupt change in thegrowing dynamics of the aggregates when a ”critical” salt concentration is reached, can also bequalitatively described within this picture.[1] A Grosberg et al Rev. Mod. Phys. 2002, 74 : 329.[2] F Bordi et al J. Phys. : Cond. Mat. 2009, 21 : 203102.[3] D Velegol and P Thwar; Langmuir 2001, 17: 7687.[4] D Truzzolillo et al Eur. Phys. J. E 29 2 (2009) 229-237.148