Pressure-Induced Formation of Diblock Copolymer "Micelles" in Supercritical Fluids. A Combined Study by Small Angle Scattering Experiments and Mean-Field Theory. I: the Critical Micellization Density Concept

Polymer and diblock copolymer phase separation in supercritical (SC) fluids was analyzed by developing a mean-field theory. A phenomenological hole theory that was extended to consider the polymer/solvent/vacancy pseudoternary mixture was used to describe the highly compressible SC fluid. In high density, the homogeneous phase was was favored while polymer aggregation was triggered by the reduced polymer-solvent contacts at low densities. The critical solvent density required for the onset of phase separation (CMD) decreased linearly with temperature, with its slope being tightly dependent on solvent and polymer properties.