Preparation of “Mushroom-like” Janus Particles by Site-Selective Surface-Initiated Atom Transfer Radical Polymerization in Aqueous Dispersed Systems

Abstract

A versatile approach for the preparation of micrometer-sized, monodisperse, "mushroom-like" Janus polymer particles in aqueous dispersed systems is proposed. The synthetic methodology of the Janus particles consists of the following two steps. The first step is the preparation of spherical poly(methyl methacrylate) (PMMA)/poly(styrene-2-(2-bromoisobutyryloxy)ethyl methacrylate) (P(S-BIEM)) Janus particles based on the internal phase separation induced by solvent evaporation from the solvent droplets dissolving the polymers. The second step is surface-initiated atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DM) using the Janus particles with ATRP initiator groups at one side of the surface as macroinitiator. As a consequence, mushroom-like PMMA/P(S-BIEM)-graft-poly(DM) Janus particles were prepared, which had pH-responsive property.

Chemically Controlled Bending of Compositionally Anisotropic Microcylinders

“…In principle, this concept is not limited to macroscopic multilayer films, but can be achieved with colloidal materials, as long as the required anisotropy can be realized and different parts of the colloidal object will respond differently to the external stimulus. In recent years, compositionally anisotropic micro-and nanoparticles have been devised using a range of different synthesis methods including microfluidic and lithographic techniques, [18] particle replication in low surface energy templates, [19] selective crosslinking of polybutadiene segments in terpolymers, [20] lithographic patterning of microspheres, [21] electrochemical [22] and photochemical [23] reduction, templating of porous membranes [24,25] and nanotubes, [26] surfactant aided growth, [27] graft polymerization, [28][29][30] and processes based on controlled surface nucleation. [31] Alternatively, electrohydrodynamic co-jetting is a method to prepare particles and fibers with multiple compartments by transferring fluids through a set of capillaries that can process dissimilar materials.…”

Structured microparticles with tailored properties produced by membrane emulsification

“…"Mushroom-like" PMMA/P(St-co-BIEM)-g-PDM Janus particles with pH-responsive PDM half-shells were fabricated by surface-initiated atom transfer radical polymerization (ATPR) of 2-(dimethylamino)ethylmethacrylate (DM) using spherical PMMA/P(St-co-BIEM) Janus particles with bromine end groups at one side of the surface as macroinitiator (Tanaka et al, 2010) (Figure 13c). …”

“…In addition, the 25 polymer swelling weakens cohesive intermolecular forces between the two polymers due to reduced entanglement between PMMA and P(St-co-BIEM) chains at the interface. When the interfacial stresses caused by uneven swelling of the two hemispheres overcome cohesive forces between them, Janus particles split into two hemispheres, as shown in Figure 13c."Mushroom-like" PMMA/P(St-co-BIEM)-g-PDM Janus particles with pH-responsive PDM half-shells were fabricated by surface-initiated atom transfer radical polymerization (ATPR) of 2-(dimethylamino)ethylmethacrylate (DM) using spherical PMMA/P(St-co-BIEM) Janus particles with bromine end groups at one side of the surface as macroinitiator (Tanaka et al, 2010) (Figure 13c). …”

High-pressure Homogenizer Design

“…(a) A micrograph of droplets formed on the surface of SPG membrane in DME ; (b) Micrographs of droplets before PME and after passing 5 times through 8-mSPG membrane . prepared by DME, interfacial polymerisation and plasma-graft pore-filling polymerization (Chu et al, 2002); (c) "Mushroom-like" Janus particles prepared by DME, internal phase separation and surface-initiated atom transfer radical polymerisation (ATRP) (Tanaka et al, 2010); (d) Silica-encapsulated magnetite nanoparticle clusters prepared by DME, solvent pervaporation and sol-gel coating (Chang and Hatton, 2012); (e) PLGA particles coated with silica nanoparticles prepared by layer-by-layer electrostatic deposition of poly(allylamine hydrochloride) (PAH) and silica nanoparticles onto PLGA particles produced by DME ( …”