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Complementary light scattering and synchrotron small-angle X-ray scattering studies of the micelle-to-unimer transition of polysulfobetaines
Doncom, K.E.B. Pitto-Barry, Anaïs Willcock, H. Lu, A. McKenzie, B.E. Kirby, N. O'Reilly, R.K.
Doncom, K.E.B.
Pitto-Barry, Anaïs
Willcock, H.
Lu, A.
McKenzie, B.E.
Kirby, N.
O'Reilly, R.K.
Publication Date
2015-03-19
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© 2015 The Authors. This is an Open Access article distributed under the
Creative Commons CC-BY license (http://creativecommons.org/licenses/by/3.0/)
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2015-03-19
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Abstract
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.
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Doncom KEB, Pitto-Barry A, Willcock H 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(8): 3666-3676.
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