A. Vrij discusses the incompatibility of polymer solutions and colloidal dispersions, focusing on the potential of average force (V(r)) and the second virial coefficient (B₂). He shows that adding particles identical to the pair considered decreases V(r) and B₂, especially for high molecular weight polymers. This destabilization is due to "volume restriction" and "osmotic" effects, leading to polymer expulsion between particles. The predictions align with some experimental results. Light scattering is a useful tool for studying these stability issues. Incompatibility between two polymers in a single solvent, where one is masked, is also discussed. The lecture covers the thermodynamic stability of colloids, the role of steric stabilization, and the effects of polymer addition on colloidal mixtures. It includes examples of hard spheres and polymer molecules, showing how the second virial coefficient and adsorption change with concentration. The lecture also discusses the "osmotic effect" and its role in destabilizing polymer colloids. Experimental evidence, such as creaming rate, flocculation, and microemulsion behavior, supports these findings. Light scattering experiments are used to determine the second virial coefficient and adsorption in polymer colloidal mixtures. The results show that the second virial coefficient can become negative, indicating phase separation. The lecture concludes with the importance of considering both "volume restriction" and "osmotic" effects in understanding colloidal stability.A. Vrij discusses the incompatibility of polymer solutions and colloidal dispersions, focusing on the potential of average force (V(r)) and the second virial coefficient (B₂). He shows that adding particles identical to the pair considered decreases V(r) and B₂, especially for high molecular weight polymers. This destabilization is due to "volume restriction" and "osmotic" effects, leading to polymer expulsion between particles. The predictions align with some experimental results. Light scattering is a useful tool for studying these stability issues. Incompatibility between two polymers in a single solvent, where one is masked, is also discussed. The lecture covers the thermodynamic stability of colloids, the role of steric stabilization, and the effects of polymer addition on colloidal mixtures. It includes examples of hard spheres and polymer molecules, showing how the second virial coefficient and adsorption change with concentration. The lecture also discusses the "osmotic effect" and its role in destabilizing polymer colloids. Experimental evidence, such as creaming rate, flocculation, and microemulsion behavior, supports these findings. Light scattering experiments are used to determine the second virial coefficient and adsorption in polymer colloidal mixtures. The results show that the second virial coefficient can become negative, indicating phase separation. The lecture concludes with the importance of considering both "volume restriction" and "osmotic" effects in understanding colloidal stability.