%0 Journal Article
%A Cors, Marian
%A Wiehemeier, Lars
%A Wrede, Oliver
%A Feoktystov, Artem
%A Cousin, Fabrice
%A Hellweg, Thomas
%A Oberdisse, Julian
%T Contrast variation SANS measurement of shell monomer density profiles of smart core–shell microgels
%J Soft matter
%V 16
%N 7
%@ 1744-6848
%C London
%I Royal Soc. of Chemistry
%M FZJ-2020-00692
%P 1922-1930
%D 2020
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:31995091
%U <Go to ISI:>//WOS:000527137300020
%R 10.1039/C9SM02036E
%U https://juser.fz-juelich.de/record/873380