Beyond simple depletion: phase behaviour of colloid-star polymer mixtures

Significant progress has been made in the last decade in understanding mixt ures of hard-sphere colloids and (smaller) non-adsorbing, ideal, linear pol ymers. We introduce extra complexity into this simple model system by repla cing the linear polymers with star-branched polymers with increasing functi onality but constant radius of gyration. The observed phase diagrams, inter preted in light of what is known about hard-sphere colloid plus linear poly mer and binary-hard-sphere mixtures, suggest that 32-arm stars are close to behaving hard-sphere-like in colloid-star mixtures at this size ratio.