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.

Publication DOI: https://doi.org/10.1039/c8sc00762d
Divisions: Engineering & Applied Sciences
Engineering & Applied Sciences > Chemical Engineering & Applied Chemistry
Additional Information: This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Full Text Link: http://www.scop ... tnerID=MN8TOARS
Related URLs: https://pubs.rs ... 2D#!divAbstract (Publisher URL)
PURE Output Type: Article
Published Date: 2018-04-02
Accepted Date: 2018-04-01
Authors: Derry, Matthew J. ( 0000-0001-5010-6725)
Mykhaylyk, Oleksandr O.
Ryan, Anthony J.
Armes, Steven P.

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