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Complementary light scattering and synchrotron small-angle X-ray scattering studies of the micelle-to-unimer transition of polysulfobetaines

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posted on 06.05.2016, 11:25 by Kay E.B. Doncom, Anais Pitto-Barry, Helen WillcockHelen Willcock, Annhelen Lu, Beulah E. McKenzie, Nigel Kirby, Rachel K. O'Reilly
AB and ABA di- and triblock copolymers where A is the hydrophilic poly(oligoethylene glycol methacrylate) (POEGMA) block and B is a thermo-responsive sulfobetaine block [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (PDMAPS) were synthesised by aqueous RAFT polymerisation with narrow dispersity (ĐM ≤ 1.22), as judged by aqueous SEC analysis. The di- and triblock copolymers self-assembled in salt-free water to form micelles with a PDMAPS core and the self-assembly of these polymers was explored by SLS and TEM analysis. The micelles were shown, by DLS analysis, to undergo a micelle-to-unimer transition at a critical temperature, which was dependent upon the length of the POEGMA block. Increasing the length of the third, POEGMA, block decreased the temperature at which the micelle-to-unimer transition occurred as a result of the increased hydrophilicity of the polymer. The dissociation of the micelles was further studied by SLS and synchrotron SAXS. SAXS analysis revealed that the micelle dissociation began at temperatures below that indicated by DLS analysis and that both micelles and unimers coexist. This highlights the importance of using multiple complementary techniques in the analysis of self-assembled structures. In addition the micelle-to-unimer morphology transition was employed to encapsulate and release a hydrophobic dye, Nile Red, as shown by fluorescence spectroscopy.

Funding

The authors would like to thanks the EPSRC and the University of Warwick Postgraduate Research Scholarship for funding. The University of Warwick Research Development Fund and the Swiss National Science Foundation are also acknowledged for financial support.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Published in

Soft Matter

Volume

11

Issue

18

Pages

3666 - 3676 (11)

Citation

DONCOM, K.E.B. ... et al, 2015. Complementary light scattering and synchrotron small-angle X-ray scattering studies of the micelle-to-unimer transition of polysulfobetaines. Soft Matter, 11 (18), pp. 3666 - 3676.

Publisher

Royal Society of Chemistry

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution 3.0 Unported (CC BY 3.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/by/3.0/

Acceptance date

19/03/2015

Publication date

2015

Notes

This is an Open Access article published by the Royal Society of Chemistry and licensed under the terms of the Creative Commons Attribution 3.0 Licence, http://creativecommons.org/licenses/by/3.0/

ISSN

1744-6848

Language

en

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