Phase transitions and gelation of silica-polystyrene mixtures in benzene.

We have performed experiments on mixtures of sterically stabilised silica particles and large poly(styrene) polymers in benzene. Using this model system, we were able to independently vary short and long ranged attractive interactions by changing the temperature and/or the polymer concentration. We show that the addition of long ranged attractions to particles with initially only short ranged attractions leads to the appearance of a gas-liquid phase transition. Our results are in accordance with earlier theoretical predictions.