The present talk is aimed at theoretical and experimental determination on thermodynamic phase diagrams of binary crystalline polymer blends and dynamics of phase transitions involving the competition between liquid-liquid phase separation and liquid-solid phase transition, specifically solidification of polymer crystals driven by thermal-quenching. We will discuss i) thermodynamic phase equilibria of crystalline polymer blends, ii) development of diverse crystal polymorphs during isothermal quenching, and iii) dynamics of hierarchical morphology subjected to thermal gradient driven by liquid carbon dioxide (CO2) spraying. To elucidate formation of diverse crystal polymorphs, phase diagrams of binary azobenzene/diacrylate mixture as well as azobenzene/nematic liquid crystalline solution were first established experimentally and tested theoretically in the context of combined free energy of Flory-Huggins theory for liquid-liquid demixing and phase field theory for crystallization. In an effort to understand the effect of local thermal gradients on hierarchical organization of single crystal polymorphs, the azobenzene/nematic liquid crystal blend sample was sprayed with compressed CO2. The liquid CO2 spraying generates spatial variations of local temperatures leading to local thermal gradients, which in turn drives the faceted single crystals to undergo hierarchical organization into a so-called ‘spherulite’. The present paper is the first to demonstrate the development of single crystal polymorph upon spraying with liquid CO2, thereby creating localized thermal gradients. Of particular interest is the formation of a hierarchical spherulitic structure composed of lamellar aggregates, whereby discrete single crystal polymorphs grow on the nematic defect (i.e., disclination), fanning out from a common core. It should be emphasized that the present aggregate model of discrete single crystals is an alternative account for spherulitic growth.Supported by NSF-DMR1502543