Hybrid Hairy Two-Dimensional Nanostructures with Tunable Morphologies by Inclusion Crystallization of Lead Bromide...

We report the formation of hybrid hairy nanostructures composed of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) and lead bromide (PbBr₂) complexes in 1,3,5-trimethylbenzene (TMB). In this system, TMB acts as a selective solvent (good for the PS block and bad for the PEO block) while serving as a nonsolvent for PbBr₂. Although PbBr₂ is insoluble in neat TMB, its complexation with PS-b-PEO promotes the formation of the [PbBr₃]^- and [PbBr₄]^2- complexes. These complexes coordinate with the ether groups of the PEO block, forming host-guest interactions that drive the inclusion crystallization of two-dimensional (2D) hybrid nanostructures, including irregular nanosheets and polygonal nanoplates. The morphology of these nanostructures strongly depends on the PS-b-PEO/PbBr₂ weight ratio. Higher ratios (20/100 and 20/200) favor irregular nanosheets, while lower ratios (20/10) favor polygonal nanoplates. Structural analysis reveals that the irregular nanosheets adopt an orthorhombic Cmca lattice (a = 23.53 Å, b = 4.20 Å, c = 33.22 Å), whereas the polygonal nanoplates exhibit a hexagonal P6mm lattice (a_hex = 13.954 Å, γ = 120°). Both types of 2D structures are decorated with ultrasmall PbBr₂ nanoparticles encapsulated by PS-b-PEO chains. The PEO blocks coordinate to nanoparticle surfaces, while PS blocks swell in the TMB. This synergistic process integrates PbBr₂ complexation, host-guest coordination, inclusion crystallization, and block copolymer-mediated nanoparticle assembly. In spin-coated films, polygonal nanoplates preferentially adopt edge-on orientations, while irregular nanosheets lie flat-on. These findings offer insights into block copolymer templating of 2D organic-inorganic hybrid nanostructures.