A. Habicht, W. Schmolke, F. Lange, K. Saalwächter, S. Seifert.
The Non-effect of Polymer-Network
Inhomogeneities in Microgel Volume Phase
Transitions: Support for the
Macromol. Chem. Phys. 215, 1116-1133 (2014).
Thermoresponsive polymer gels exhibit pronounced swelling and deswelling upon changes in
temperature, making them attractive for applications in sensing and actuation. This volume
phase transition can be discussed in terms of mean-fi eld theoretical pictures to assess at
which conditions it occurs continuously or discontinuously. However, this treatment disregards
static nano- and micrometer-scale inhomogeneities in gel polymer networks, which are
a common feature of these materials. To check for the impact of such structural complexity,
droplet-based microfl uidics are used to fabricate sub-millimeter-sized gel particles that exhibit
critical compositions at the border between continuous to discontinuous
volume phase transitions, along with determined
static spatial polymer-network heterogeneity on the nanometer
and micrometer length scales, which is characterized
by low-fi eld NMR. These different microgels are then used
to study their swelling and deswelling volume phase transitions
from a sub-millimeter perspective. In this investigation,
microgel particles with similar content of crosslinker exhibit
similar swelling and deswelling, independent of their extent
of static polymer-network inhomogeneity, in agreement with
mean-fi eld theoretical predictions.