Liquid-Liquid Phase Separation, Crystallization, and Solvent Evaporation in Relation to Microsphere Formation from...

Thermally induced phase separation (TIPS) is a convenient method to prepare polymer micro/nanoparticles from synthesized polymers. However, the mapping relationship between the phase separation dynamic in the polymer/solvent system and the morphological structure of further separated polymer micro/nanoparticles from the solvent has not yet been established. Here, UV-vis and DSC were used to characterize the phase separation and crystallization temperatures of polymer/solvent systems. In addition to optical observation, a rotational rheometer was innovatively applied to investigate the TIPS process. The evolution of TIPS in polymer/solvent systems under a sealed environment was thoroughly analyzed. Furthermore, opening evaporation and restricted evaporation were introduced as solid-liquid separation methods to investigate the size distribution, morphology, crystallization, and thermal properties of TIPS products from polymer/solvent systems at different temperatures. Through the comparative analysis, combined with the Flory-Huggins theory, the microsphere formation mechanism of isotactic polypropylene (iPP)/decalin solution in the evaporation process has been successfully summarized.