Tunable attractions directing nonequilibrium states in dispersions of hard rods

The effect of attractive interactions on the phase behavior of colloidal hard rods has been studied by the addition of nonadsorbing polymer. In these rod-polymer mixtures, four pathways of phase separation can be distinguished: nucleation and growth, spinodal decomposition, aggregation, and gelation. The first three mechanisms give rise to macroscopic phase separation, whereas for the latter mechanism this is not necessarily the case. The observed phenomena are explained on the basis of an interplay between the position of both the spinodal line and the glass line, the overall composition of the sample, and the range of the potential.