Hierarchically Porous Carbon Materials from Self-Assembled Block Copolymer/Dopamine Mixtures

Structural Evolution of a Polystyrene-Block-Poly(Ethylene Oxide) Block Copolymer in Tetrahydrofuran/Water Cosolvents

This study aims to quantitatively investigate the effect of water content on the self-assembly behavior of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) in tetrahydrofuran/water cosolvents by small-angle X-ray scattering. PS-b-PEO chains preferentially form fractal aggregates at a dilute concentration in neat tetrahydrofuran (THF). By adding a small amount of water into THF, PS-b-PEO forms gelled networks. The gelled networks have correlated inhomogeneities, which were generated through mesophase separation. These gelled networks are not present when PS-b-PEO is dissolved in THF/methanol and THF/ethanol cosolvents. The substitution of water with 12 M HCl reduces the viscosity of the gelled networks. Those results indicate that the gelled networks of PS-b-PEO need hydrogen bonds formed from surrounding water molecules to be bridging agents, which connect different PEO block chains together. Upon increasing the water content in THF/water cosolvents, dispersed micelles with a core-shell conformation or aggregated micelles preferentially coexist with fractal aggregates.

Polymer Brush-Induced Hollow Colloids via Diffusion-Controlled Silication

We report on a new strategy to synthesize asymmetrical hollow colloidal particles by exploiting limited chemical diffusion that occurs at the periphery of a solvated polymer brush on the particle surface. The polymer brush-in our case poly(glycidyl methacrylate)-bears hydroxyl groups upon hydrolysis and is partially cross-linked under the Stöber condition of silication. Desolvation of the polymers creates a cavity. While elucidating this new mechanism, we demonstrate that particles with various types of cavities and tunable properties can be synthesized, including the ones bearing hemispherical and crescent shapes, as well as particles with wrinkled surfaces. Furthermore, we show that the hollow particles adopt preferred orientations because of their shape and composition attributes, which is further explored to facilitate the confined synthesis of nanocrystals.