Inclusion Crystallization Self-Assembly in Hybrids of Polystyrene- <i>Block</i> -Poly(Ethylene Oxide) and Lead(II) Bromide in Tetrahydrofuran

This study investigates PbBr2 complexation, inclusion crystallization, and block copolymer–directed self-assembly in tetrahydrofuran (THF), using polystyrene-block-poly(ethylene oxide) (PS-b-PEO) as a structure-directing or crystallization-modulating agent. Here, we demonstrate that THF, a neutral solvent, enables a distinct complexation pathway: at low PS-b-PEO concentrations, [PbBr3]− complexes dominate, whereas mononuclear [PbBr4]2– and polynuclear [Pb4Br11]3– and [Pb2Br5]− complexes become more prominent at higher polymer loadings. This solvent environment gives rise to diverse mesoscale morphologies and molecular-scale polymorphs through competing driving forces of crystallization of the PEO-[PbxBry]2x−y complex blocks and the self-assembly tendency of the PS-b-(PEO-[PbxBry]2x−y complex) diblock molecules into micellar aggregates. At low PS-b-PEO concentrations, compact microplates primarily form via nucleation-limited aggregation, coexisting with small amounts of dense polygonal nanoplates and seaweed-like structures. The compact microplates are composed of large hexagonal complex crystals, while the dense polygonal nanoplates contain smaller hexagonal crystals. In contrast, the seaweed-like structures consist of orthorhombic complex crystals. As the PS-b-PEO concentration increases, the self-assembly tendency of the PS-b-(PEO–[PbxBry]2x−y complex) diblock molecules into cylindrical micellar aggregates becomes dominant over crystallization of the PEO–[PbxBry]2x−y complex blocks. Consequently, compact microplates evolve into cheese-like microplates that retain hexagonal symmetry, although their overall abundance significantly decreases. Instead, seaweeds, loose dendrites, and fibers─composed of orthorhombic complex crystals─emerge as the dominant morphologies. These findings shed light on the importance of solvent quality in tuning crystallization pathways and structural hierarchies, providing new insights into the design of inclusion crystallization and soft-matter self-assembly in neutral solvent systems.