Prismatic Block Copolymer Hexosomes

Bicontinuous Block Copolymer Microparticles through Hydrogen-Bonding-Mediated Dual Phase Separation between Polymer Segments and Fluorinated Additives

Bicontinuous microparticles have advanced transport, mechanical, and electrochemical properties and show promising applications in energy storage, catalysis, and other fields. However, it remains a great challenge to fabricate bicontinuous microparticles of block copolymers (BCPs) by controlling the microphase separation due to the extremely narrow region of a bicontinuous structure in the phase diagram. Here, we demonstrate a strategy to balance the phase separation of BCPs and fluorinated additives at different length scales in emulsion droplets, providing a large window to access bicontinuous microparticles. The key point is to simultaneously introduce contradictory attractive-repulsive interactions between poly(4-vinylpyridine)-containing BCPs and carboxylated perfluorinated additives. Hydrogen bonding between poly(4-vinylpyridine) and carboxyl groups, as an attractive interaction, directs the microphase separation between BCPs and additives. Meanwhile, the repulsive interaction due to the high immiscibility between perfluoroalkyl residues and BCPs induces macrophase separation. The compromise of attractive-repulsive interactions triggers the formation of bicontinuous microparticles in a large phase space. In addition, the vulnerable nature of hydrogen bonding provides a flexible route for reversibly shaping BCP assemblies. This work establishes a platform for fabricating structured BCP microparticles of which the structures are hardly accessible through traditional solution self-assembly.

Photocleavable Polymer Cubosomes: Synthesis, Self-Assembly, and Photorelease

Polymer cubosomes (PCs) are a recent class of self-assembled block copolymer (BCP) microparticles with an accessible periodic channel system. Most reported PCs consist of a polystyrene scaffold, which provides mechanical stability for templating but has a limited intrinsic functionality. Here, we report the synthesis of photocleavable BCPs with compositions suitable for PC formation. We analyze the self-assembly mechanism and study the model release of dyes during irradiation, where the transition of the BCPs from amphiphilic to bishydrophilic causes the rapid disassembly of the PCs. A combination of modeling and experiment shows that the evolution of PCs proceeds first via liquid-liquid phase separation into polymer-rich droplets, followed by microphase separation within this droplet confinement, and finally, membrane reorganization into high internal order. This insight may encourage exploration of alternative preparation strategies to better control the size and homogeneity of PCs.

Impact of channel nanostructures of porous carbon particles on their catalytic performance

Mesoporous carbon particles have great potential due to their unique structural properties as support materials for catalytic applications. Particle shapes and channel nanostructures of mesoporous carbon particles can determine the reactant/product transport efficiency. However, the role of the channel nanostructure in the catalytic reaction has not been much explored. Herein, we introduce a facile method to fabricate a series of porous carbon particles (PCPs) with controlled channel exposure on the carbon surface and investigate the impact of the channel nanostructure of the PCPs on the catalytic activity. By employing a membrane emulsification method with a controlled solvent evaporation rate, we fabricate block copolymer (BCP) particles with uniform size and regulated degrees of cylindrical channel exposed to the particle surface. Followed by the carbonization of the BCP particles, a low amount (1.3 wt%) of Pt is incorporated into the PCP series to investigate the impact of channel nanostructures on the catalytic oxidation reaction of o-phenylenediamine (OPD). Specifically, PCP featuring highly open channel nanostructures shows a high reaction rate constant of 0.154 mM-1 s-1 for OPD oxidation, showing 5.5 times higher catalytic activity than those of closed channel nanostructures (0.028 mM-1 s-1). This study provides a deeper understanding of the impact of channel nanostructure within mesoporous carbon particles on catalytic activity.