Non-equilibrium behaviour of colloid-polymer mixtures

✍ Scribed by W.C.K. Poon; A.D. Pirie; M.D. Haw; P.N. Pusey

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 536 KB
• Volume: 235
• Category: Article
• ISSN: 0378-4371
• DOI: 10.1016/s0378-4371(96)00332-9

✦ Synopsis

Moderate concentrations of a small non-adsorbing polymer cause a suspension of colloidal particles to phase-separate into coexisting colloidal fluid and crystal via the 'depletion' mechanism. At higher polymer concentrations, crystallization is suppressed, and a variety of non-equilibrium aggregation behaviour is observed. We report the results of small-angle laser light scattering studies of aggregation in a model system -colloidal PMMA + polystyrene. In all cases, 'rings' in the small-angle scattering are observed. The different temporal behaviour of these small-angle scattering rings allowed us to classify the non-equilibrium region into three regimes, 'nucleationlike', 'spinodal-like' and 'transient gelation'. It is suggested that non-equilibrium behaviour is 'switched on' by a hidden, metastable gas-liquid binodal. Different regimes of aggregation behaviour are controlled by the nucleation-spinodal cross-over and the transient percolation lines within this binodal.