In Situ Small-Angle X-ray Scattering Studies During Reversible Addition–Fragmentation Chain Transfer Aqueous Emulsion Polymerization (Brotherton e.pdf (7.5 MB)
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In situ small-angle x-ray scattering studies during reversible addition–fragmentation chain transfer aqueous emulsion polymerization

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journal contribution
posted on 13.09.2019, 13:17 authored by Emma E Brotherton, Fiona HattonFiona Hatton, Amy A Cockram, Matthew J Derry, Adam Czajka, Erik J Cornel, Paul D Topham, Oleksandr O Mykhaylyk, Steven P Armes
Polymerization-induced self-assembly (PISA) is a powerful platform technology for the rational and efficient synthesis of a wide range of block copolymer nano-objects (e.g., spheres, worms or vesicles) in various media. In situ small-angle X-ray scattering (SAXS) studies of reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization have previously provided detailed structural information during self-assembly (see M. J. Derry et al., Chem. Sci. 2016 , 7 , 5078 - 5090 ). However, conducting the analogous in situ SAXS studies during RAFT aqueous emulsion polymerizations poses a formidable technical challenge because the inherently heterogeneous nature of such PISA formulations requires efficient stirring to generate sufficiently small monomer droplets. In the present study, the RAFT aqueous emulsion polymerization of 2-methoxyethyl methacrylate (MOEMA) has been explored for the first time. Chain extension of a relatively short non-ionic poly(glycerol monomethacrylate) (PGMA) precursor block leads to the formation of sterically-stabilized PGMA-PMOEMA spheres, worms or vesicles, depending on the precise reaction conditions. Construction of a suitable phase diagram enables each of these three morphologies to be reproducibly targeted at copolymer concentrations ranging from 10 to 30% w/w solids. High MOEMA conversions are achieved within 2 h at 70 °C, which makes this new PISA formulation well-suited for in situ SAXS studies using a new reaction cell. This bespoke cell enables efficient stirring and hence allows in situ monitoring during RAFT emulsion polymerization for the first time. For example, the onset of micellization and subsequent evolution in particle size can be studied when preparing PGMA29-PMOEMA30 spheres at 10% w/w solids. When targeting PGMA29-PMOEMA70 vesicles under the same conditions, both the micellar nucleation event and the subsequent evolution in the diblock copolymer morphology from spheres to worms to vesicles are observed. These new insights significantly enhance our understanding of the PISA mechanism during RAFT aqueous emulsion polymerization.

Funding

Advanced Investigator grant (PISA 320372)

Established Career Fellowship in Particle Technology (EP/ R003009).

The Leverhulme Trust (RPG-2016-330).

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Published in

Journal of the American Chemical Society

Volume

141

Issue

34

Pages

13664 - 13675

Publisher

American Chemical Society (ACS)

Version

VoR (Version of Record)

Rights holder

© American Chemical Society

Publisher statement

This is an Open Access Article. It is published by American Chemical Society under the Creative Commons Attribution 4.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/

Publication date

2019-07-31

Copyright date

2019

ISSN

0002-7863

eISSN

1520-5126

Language

en

Depositor

Dr Fiona Hatton

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