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Issue 7, 2020
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Contrast variation SANS measurement of shell monomer density profiles of smart core–shell microgels

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Abstract

The radial density profile of deuterated poly(N,n-propyl acrylamide) shell monomers within core–shell microgels has been studied by small-angle neutron scattering in order to shed light on the origin of their linear thermally-induced swelling. The poly(N-isopropyl methacrylamide) core monomers have been contrast-matched by the H2O/D2O solvent mixture, and the intensity thus provides a direct measurement of the spatial distribution of the shell monomers. Straightforward modelling shows that their structure does not correspond to the expected picture of a well-defined external shell. A multi-shell model solved by a reverse Monte Carlo approach is then applied to extract the monomer density as a function of temperature and of the core crosslinking. It is found that most shell monomers fill the core at high temperatures approaching synthesis conditions of collapsed particles, forming only a dilute corona. As the core monomers tend to swell at lower temperatures, a skeleton of insoluble shell monomers hinders swelling, inducing the progressive linear thermoresponse.

Graphical abstract: Contrast variation SANS measurement of shell monomer density profiles of smart core–shell microgels

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Article information


Submitted
12 Oct 2019
Accepted
19 Jan 2020
First published
20 Jan 2020

Soft Matter, 2020,16, 1922-1930
Article type
Paper

Contrast variation SANS measurement of shell monomer density profiles of smart core–shell microgels

M. Cors, L. Wiehemeier, O. Wrede, A. Feoktystov, F. Cousin, T. Hellweg and J. Oberdisse, Soft Matter, 2020, 16, 1922
DOI: 10.1039/C9SM02036E

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