Structure Regulation of Block Copolymer Assemblies in Emulsion Droplets by Adding a Selective Solvent.

Generally, nanostructured polymer particles are prepared by 3D confined self-assembly (3D-CSA) of block copolymers (BCPs), while micelles are obtained through self-assembly of BCPs in dilute solutions. Herein, a facile yet robust strategy is developed to regulate the assembled structures of BCP, poly(styrene-block-4-vinylpyridine) (PS-b-P4VP), from nanostructured particles to micelles. The assemblies are prepared by an emulsion-solvent diffusion-induced self-assembly route, which is conducted by dialysis. A key feature of this strategy is that a P4VP-selective solvent (e.g., ethanol) is added to the dialysate to tune the interfacial behavior of the droplets and assembled structures of PS-b-P4VP. The authors' results reveal that in the presence of slight ethanol, the surface and internal structural transitions of nanostructured particles are caused by changes in the interfacial selectivity and packing parameter. Interestingly, interfacial instability, which results in the formation of micelles, is observed when the dialysate contains 50 vol% ethanol or more. The reason can be ascribed to the decreased interface tension, which is induced by the increase in ethanol and enhanced solubility of P4VP. This facile strategy provides a new opportunity to bridge the gap between traditional 3D-CSA and solution self-assembly of BCPs, offering a promising route to engineer morphologies and nanostructures of polymeric assemblies.

A Versatile 3D-Confined Self-Assembly Strategy for Anisotropic and Ordered Mesoporous Carbon Microparticles.

Mesoporous carbon microparticles (MCMPs) with anisotropic shapes and ordered structures are attractive materials that remain challenging to access. In this study, a facile yet versatile route is developed to prepare anisotropic MCMPs by combining neutral interface-guided 3D confined self-assembly (3D-CSA) of block copolymer (BCP) with a self-templated direct carbonization strategy. This route enables pre-engineering BCP into microparticles with oblate shape and hexagonal packing cylindrical mesostructures, followed by selective crosslinking and decorating of their continuous phase with functional species (such as platinum nanoparticles, Pt NPs) via in situ growth. To realize uniform in situ growth, a "guest exchange" strategy is proposed to make room for functional species and a pre-crosslinking strategy is developed to preserve the structural stability of preformed BCP microparticles during infiltration. Finally, Pt NP-loaded MCMPs are derived from the continuous phase of BCP microparticles through selective self-templated direct carbonization without using any external carbon source. This study introduces an effective concept to obtain functional species-loaded and N-doped MCMPs with oblate shape and almost hexagonal structure (p6mm), which would find important applications in fuel cells, separation, and heterogeneous catalysis.