Complex viscosity behavior and cluster formation in attractive colloidal   systems
  The increase of the viscosity, which is observed in attractive colloidal systems by varying the temperature or the volume fraction, can be related to the formation of structures due to particle aggregation. In particular we have studied the non trivial dependence of the viscosity from the temperature and the volume fraction in the copolymer-micellar system L64. The comparison of the experimental data with the results of numerical simulations in a simple model for gelation phenomena suggests that this intriguing behavior can be explained in terms of cluster formation and that this picture can be quite generally extended to other attractive colloidal systems. 
F. Mallamace, S. H. Chen, A.Coniglio, L. de Arcangelis, E. Del Gado   and A. Fierro