Preparation of Non‐Spherical Janus Particles via an Orthogonal Dissolution Approach

Abstract

Post‐synthesis modifications are valuable tools to alter functionalities and induce morphology changes in colloidal particles. Non‐spherical polymer particles with Janus characteristics have been prepared by combining seeded growth polymerization and selective dissolution. First, spherical polystyrene (PS) particles have been swollen with methyl methacrylate (MMA) with an activated swelling method. This was followed by polymerization that led to particles with two well‐separated faces: one made of PS and the second of PMMA. Subsequently, non‐spherical particles were obtained by exposing the Janus colloids to various solvents. Using the two polymers' orthogonal solubility, solvents were identified to selectively dissolve only one face, leading to hemispherical PS or PMMA particles. We further investigated how changing the composition of the PMMA face – by either co‐polymerization with glycidyl methacrylate or by adding a cross‐linker – affects the particles’ morphology. The poly‐methacrylate face can gain total or partial resistance towards the solvents, resulting in intriguing shapes, such as mushroom‐like and Janus dimpled particles. The dissolution mechanisms were investigated via optical microscopy, where total or partial dissolutions could be directly observed. Lastly, prematurely quenching the dissolution of the particle's lobes with water could be used to control the Janus mushroom‐like particle aspect ratio.This article is protected by copyright. All rights reserved

Revealing the Formation Dynamics of Janus Polymer Particles: Insights from Experiments and Molecular Dynamics

“…The same centrifugation procedure was used to purify the particles at the very end of the polymerization process. As reported in our previous work, 28 the particles have a very narrow size distribution, even though some large beads are also formed, which are easily separated by centrifugation.…”

Preparation of Asymmetric Al2O3-SiO2 Janus Nanoparticles in Aqueous Phase and Its Interfacial Property

“…Since then, research on Janus nanoparticles has been thriving, and they have received considerable attention due to their unique physical, chemical, and biological properties [ 8 ]. Different techniques such as masking, bottom-up assemblies, and controlled phase separation have been employed to synthesize Janus nanoparticles [ 9 , 10 ], and various Janus architectures have been created, such as cylindrical-shaped [ 11 ], dumbbell-shaped with asymmetric or snowman characters [ 12 , 13 , 14 , 15 , 16 , 17 ], mushroom-shaped [ 18 , 19 ], bowl-like [ 20 , 21 ], crescent-shaped [ 22 , 23 ], and half-raspberry-shaped structures [ 24 ]. Among these, dumbbell-like nanoparticles, as a prominent subset of Janus nanoparticles, have attracted significant interest due to their unique structure and excellent performance in various application domains, including drug delivery, catalysis, sensing, and advanced materials.…”