Tunable formation of two-dimensional nanostructures and complex crystals <i>via</i> lead( <scp>ii</scp> ) bromide complexation and inclusion crystallization with polystyrene- <i>block</i> -poly(ethylene oxide) in 1,3,5-trimethylbenzene

We report the formation of two-dimensional (2D) hairy nanostructures-irregular nanosheets and polygonal nanoplates-<i>via</i> inclusion crystallization between polystyrene-<i>block</i>-poly(ethylene oxide) (PS-<i>b</i>-PEO) and lead(II) bromide (PbBr₂) in 1,3,5-trimethylbenzene (TMB). The irregular nanosheets are composed of orthorhombic complex crystals with <i>Cmca</i> symmetry and the polygonal nanoplates are composed of hexagonal complex crystals with <i>P</i>6<i>mm</i> symmetry. Systematic variation of the PS-<i>b</i>-PEO/PbBr₂ ratio reveals that both components critically influence the morphology and crystallinity of the resulting structures. At a fixed PbBr₂ concentration (10 mg mL^-1), increasing PS-<i>b</i>-PEO content initially promotes the formation of both nanosheets and nanoplates, but at higher concentrations favors polygonal nanoplates while suppressing irregular nanosheets. Conversely, at a fixed PS-<i>b</i>-PEO level (1 mg mL^-1), increasing PbBr₂ enhances complexation as reflected in UV-vis absorbance spectra, but the formation of complex crystals behaves differently due to polymer saturation and dilution effects. WAXD analysis reveals that inclusion crystallization occurs most efficiently at moderate PbBr₂ loading (0.1 and 1 mg mL^-1) to simultaneously form a high crystallinity of orthorhombic and hexagonal complex crystals. However, excess PbBr₂ leads to the formation of crystalline PbBr₂ domains and results in the formation of irregular nanosheets with low crystallinity without forming polygonal nanoplates. These findings demonstrate that the polymer-to-salt ratio governs the polymorphism behavior and efficiency of inclusion crystallization, and further indicate that PbBr₂ complexation and crystalline ordering are decoupled processes. This work offers mechanistic insights into polymer-salt ratio-controlled inclusion crystallization, providing a tunable approach for constructing anisotropic hairy nanostructures.