Polymer Brush-Induced Hollow Colloids via Diffusion-Controlled Silication

Abstract

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.

Synthetic Strategies for Polymer Particles with Surface Concavities

“…According to the detailed process, the surface treatment-based method might be further categorized into three different strategies: surface treatment-swellingdeswelling, [198][199][200][201][202][203] swelling-coating-deswelling, [204,205] and other surface treatment-based processes. [206][207][208][209][210][211][212] Surface Treatment-Swelling-Deswelling: In this surface treatment-swelling-deswelling strategy, various surface treatment techniques have been reported to create a skin layer, including UV irradiation, [198][199][200] UV-ozone treatment, [201] oxygen plasma [202] and ion sputtering. [203] In 2011, Godinho and co-workers described the fabrication of micrometer-to millimeter-sized labyrinth-wrinkled Janus particles.…”

“…(vi) Coating-Desolvation Very recently, Wang and co-workers reported a unique strategy to synthesize wrinkled PGMA-SiO 2 core-shell particles by utilizing a diffusion-controlled silication reaction on the surface of a solvated PGMA particles (see Figure 13D). [212] Specifically, the epoxide groups of the PGMA particles are hydrolyzed under a basic condition to form soluble hydroxyl groups, leading to a well-solvated polymer brush on the particle surface. Then, silanols derived from hydrolyzed TEOS condense with the hydroxyl groups, generating a semi-hard cross-linked network or brush on the particle surface.…”

“…To date, several post-treatment methods have been proposed for the fabrication of surface-wrinkled polymer particles, which involve surface treatment-based methods, [198][199][200][201][202][203][204][205][206][207][208][209][210][211][212] microfluidic emulsification/emulsion-solvent evaporation, [213][214][215][216][217] electrospraying/solvent evaporation, [218,219] templating methods [220][221][222][223][224] and some other methods. [225][226][227]…”

“…D) Schematic illustration of the formation mechanism of wrinkled surface and Janus hollow colloids. Reproduced with permission [212]. Copyright 2020, American Chemical Society.…”

Complex Polymeric Microstructures with Programmable Architecture via Pickering Emulsion-Templated In Situ Polymerization

“…), which faces a great challenge in evaporation flux control. , The hard template-based techniques involve the etching of the template, which entails special physical/chemical post-treatments for template removal (strong acid etchant, thermal annealing, calcination, etc. ), separate synthesis of the template, and extra processing steps. ,, The microfluidics technique needs expensive special equipment, and a limited particle diameter is obtained (∼10 μm) . The freeze-drying technique necessitates a suspension temperature around −210 °C (using liquid N 2 ), and the frozen sample needs to be gradually warmed with a rate of 30 °C/h to tailor various microstructures.…”