Macromolecular Architecture-Directed Crystallization: Heterogeneous and Homogeneous Crystallization in Miktoarm Star Copolymers

Understanding how polymer architecture affects crystallization behavior is crucial for developing advanced functional materials. In this study, we investigate a series of miktoarm star-shaped copolymers composed of polystyrene (PS) and poly-(ethylene oxide) (PEO), with systematically varied PEO content (18-86 wt %) and a fixed PS arm length. Using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and small- and wide-angle X-ray scattering (SAXS/WAXS), we elucidate how intramolecular confinement within star-shaped architectures influences crystallization. At high PEO content, a core-shell morphology supports heterogeneous nucleation and bulk-like spherulitic growth. As PEO content decreases, homogeneous nucleation becomes dominant, and crystallinity is significantly suppressed due to increased confinement and reduced domain size. Our results demonstrate that molecular architecture profoundly influences the nucleation mechanism, crystallization temperature, and crystalline domain structure in PS-PEO miktoarm copolymers, offering a platform for tuning various properties of polymer materials.