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.