Issue 17, 2018

Thermoreversible crystallization-driven aggregation of diblock copolymer nanoparticles in mineral oil

Abstract

A poly(behenyl methacrylate)37 (PBeMA37) macromolecular chain transfer agent is utilized for the reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) directly in mineral oil at 90 °C. Polymerization-induced self-assembly (PISA) occurs under these conditions, yielding a series of sterically-stabilized PBeMA37–PBzMAx diblock copolymer spheres of tunable diameter as confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM) studies. Rheological studies indicate that a relatively transparent, free-flowing, concentrated dispersion of non-interacting 32 nm PBeMA37–PBzMA100 spheres at 50 °C forms a turbid, paste-like dispersion on cooling to 20 °C. Turbidimetry and differential scanning calorimetry (DSC) studies conducted on solutions of PBeMA37 homopolymer in mineral oil suggest that this switchable colloidal stability is linked to crystallization-induced phase separation exhibited by this stabilizer block. Indeed, variable-temperature small-angle X-ray scattering (SAXS) indicates that a loose mass fractal network of strongly interacting spheres is formed on cooling to 20 °C, which accounts for this thermoreversible sol–gel transition. Moreover, SAXS, DSC and wide-angle X-ray scattering (WAXS) analyses indicate that the behenyl (C22H45) side-chains first form crystalline domains comprising adjacent stabilizer chains within individual spherical nanoparticles, with subsequent crystallization between neighboring nanoparticles leading to the formation of the mass fractal aggregates.

Graphical abstract: Thermoreversible crystallization-driven aggregation of diblock copolymer nanoparticles in mineral oil

Associated articles

Supplementary files

Article information

Article type
Edge Article
Submitted
14 Feb 2018
Accepted
01 Apr 2018
First published
02 Apr 2018
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2018,9, 4071-4082

Thermoreversible crystallization-driven aggregation of diblock copolymer nanoparticles in mineral oil

M. J. Derry, O. O. Mykhaylyk, A. J. Ryan and S. P. Armes, Chem. Sci., 2018, 9, 4071 DOI: 10.1039/C8SC00762D

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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