Influence of Softness and Internal Architecture on Microgel Deswelling in Concentrated Suspensions

Micorgels are soft polymeric networks swollen in a good solvent. They can be compressed, deformed or interpenetrated in concentrated suspensions. The prevalence of one of these mechanisms depends on both the softness and the architecture of the polymer network. By probing regular, ultra-low crosslinked, and hollow-poly(N-isopropylacrylamide) based microgels we show that for the same architecture, a decrease in the amount of crosslinker during the synthesis produces a more pronounced deswelling. Small-angle neutron scattering is used to directly access the form factors of the different microgels embedded within a matrix of regular crosslinked ones. This work clarifies that to obtain compressible microgels that adapt their size in concentrated suspenions, the presence of a cavity produces higher deswelling than decreasing the amount of crosslinker during the precipitation polymerization. The latter option leads to the opposite effect and interpenetration is dominant.