Issue 22, 2020

Polymer-encapsulation of iron oxide clusters using macroRAFT block copolymers as stabilizers: tuning of the particle morphology and surface functionalization

Abstract

We report the successful synthesis of superparamagnetic latex particles with a high fraction of magnetic materials and a fast magnetic response. Commercial fatty acid-modified iron oxide (IO) nanoparticles were first assembled into spherical clusters through an emulsification/solvent evaporation method. The resulting particles were stabilized with poly(2-dimethylaminoethyl methacrylate)-b-polystyrene (PDMAEMA-b-PS) amphiphilic block copolymers obtained by RAFT, and used as seeds in the emulsion copolymerization of styrene and divinylbenzene (DVB), used as cross-linking agent. The latter revealed to be key in preserving the integrity of the clusters during the emulsion polymerization reaction, and a minimum amount (i.e. 10 wt%) was necessary to obtain stable latexes composed of a core of densely packed IO nanoparticles surrounded by a thin polymer shell. DVB also had a strong influence on the particle morphology as the core–shell morphology of the composite particles could be tuned with either a smooth polymer shell or a raspberry-like surface by adjusting the DVB-to-monomer weight ratio and the feeding conditions. The amphiphilic macroRAFT not only provides colloidal stability to the magnetic latexes, but also offers a versatile platform for the design of composite particles with tailored surface properties by an appropriate choice of the hydrophilic block. Our strategy was thus successfully extended to poly(acrylic acid)-b-polystyrene (PAA-b-PS) copolymers, leading to PAA-stabilized composite particles. Both kinds of IO-encapsulated particles showed superparamagnetic properties (magnetizations at saturation of 35 and 31 emu g−1 for PDMAEMA and PAA systems, respectively), and could thus find interesting applications as magnetic carriers in the biological field due to their thermo- (for PDMAEMA) and pH- (for PDMAEMA and PAA) responsive properties.

Graphical abstract: Polymer-encapsulation of iron oxide clusters using macroRAFT block copolymers as stabilizers: tuning of the particle morphology and surface functionalization

Supplementary files

Article information

Article type
Paper
Submitted
11 feb 2020
Accepted
10 apr 2020
First published
14 apr 2020
This article is Open Access
Creative Commons BY license

J. Mater. Chem. B, 2020,8, 4917-4929

Polymer-encapsulation of iron oxide clusters using macroRAFT block copolymers as stabilizers: tuning of the particle morphology and surface functionalization

T. R. Guimarães, M. Lansalot and E. Bourgeat-Lami, J. Mater. Chem. B, 2020, 8, 4917 DOI: 10.1039/D0TB00384K

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