SHORT-RANGE STRUCTURE OF SIMULATED FLOCS OF PARTICLES WITH BRIDGING POLYMER

Bridging flocculation of colloidal particles by adsorbing polymer is simulated in three dimensions by an off-lattice Monte Carlo model. Polymer chains are modelled as freely jointed, freely rotating, excluded volume random walks of 50 segments in length. Two types of particle-particle interaction are modelled: (i) hard-sphere repulsions, and (ii) soft-sphere repulsions. Particles and polymer interact via a square-well potential. Numerical results are presented for the effects of square-well depth and particle-particle interaction on the conformation of adsorbed polymer and the structure of particle flocs that are formed. The floc structures obtained from modelling particles with soft-sphere repulsions are compared to experimental data from small-angle neutron scattering studies, obtained from the literature. Soft-sphere repulsive interactions results in less compact floc structures, which have a more short-range, fluid-like character than those formed from hard spheres. The structure of flocs obtained from modelling soft spheres is more reminiscent of the floc structure found in experimental systems.