TY  - JOUR
AU  - Keidel, Rico
AU  - Ghavami, Ali
AU  - Lugo, Dersy M.
AU  - Lotze, Gudrun
AU  - Virtanen, Otto
AU  - Beumers, Peter
AU  - Pedersen, Jan Skov
AU  - Bardow, Andre
AU  - Winkler, Roland G.
AU  - Richtering, Walter
TI  - Time-resolved structural evolution during the collapse of responsive hydrogels: The microgel-to-particle transition
JO  - Science advances
VL  - 4
IS  - 4
SN  - 2375-2548
CY  - Washington, DC [u.a.]
PB  - Assoc.
M1  - FZJ-2018-01484
SP  - eaao7086
PY  - 2018
AB  - Adaptive hydrogels, often termed smart materials, are macromolecules whose structure adjusts to external stimuli. Responsive micro- and nanogels are particularly interesting because the small length scale enables very fast response times. Chemical cross-links provide topological constraints and define the three-dimensional structure of the microgels, whereas their porous structure permits fast mass transfer, enabling very rapid structural adaption of the microgel to the environment. The change of microgel structure involves a unique transition from a flexible, swollen finite-size macromolecular network, characterized by a fuzzy surface, to a colloidal particle with homogeneous density and a sharp surface. In this contribution, we determine, for the first time, the structural evolution during the microgel-to-particle transition. Time-resolved small-angle x-ray scattering experiments and computer simulations unambiguously reveal a two-stage process: In a first, very fast process, collapsed clusters form at the periphery, leading to an intermediate, hollowish core-shell structure that slowly transforms to a globule. This structural evolution is independent of the type of stimulus and thus applies to instantaneous transitions as in a temperature jump or to slower stimuli that rely on the uptake of active molecules from and/or exchange with the environment. The fast transitions of size and shape provide unique opportunities for various applications as, for example, in uptake and release, catalysis, or sensing.
LB  - PUB:(DE-HGF)16
C6  - pmid:29740608
UR  - <Go to ISI:>//WOS:000431374900018
DO  - DOI:10.1126/sciadv.aao7086
UR  - https://juser.fz-juelich.de/record/843966
ER  -