In a selective solvent, diblock copolymer exhibits both bulk phase separation and nano phase separation. The hetero-segment Statistical Associating Fluid Theory (SAFT) is demonstrated to represent the cloud-point pressures of homopolymers and block copolymers in subcritical and supercritical propane. The SAFT framework is also exploited to analyze the Critical Micelle Temperature and Critical Micelle Pressure data measured for polyisoprene and polybutadiene in propane.