Colloid and Polymer Science

, Volume 296, Issue 8, pp 1341–1352 | Cite as

Polymer- vs. colloidal-type viscoelastic mechanics of microgel pastes

  • Simon Kunz
  • Maria Pawlik
  • Wolfgang SchärtlEmail author
  • Sebastian SeiffertEmail author
Original Contribution


Microgels can form viscoelastic pastes upon packing. For small microgels with low crosslinking density, however, it is unclear if the yielding of these pastes is based on colloid analogous breaking of cages or disentanglement of polymer chain ends at the microgel surface. To answer this question, we investigate pastes of 100-nm-sized poly(N-isopropylacrylamide) pNIPAAm microgels and study the effect of the microgel crosslinking density on the liquid-to-solid transition and the shear-dependent yielding. Our densely crosslinked particles exhibit yield curves with a peak in the loss modulus, typical for shear melting of colloidal crystals due to cage breaking, whereas our microgels with < 10 mol% crosslinker show no loss peak. We conclude that with decreasing crosslinker content, dangling ends and other defects in the microgel polymer network allow for marked interparticle interpenetration, shifting the liquid-to-solid transition to packing fractions > 10 and changing the yielding mechanism from colloid analogous cage breaking to polymer analogous chain disentanglement.


Colloids Microgels Rheological properties Viscoelasticity 



We thank Dr. K. Fischer for performing static and dynamic light scattering measurements to determine the ρ ratio for our soft microgels of crosslinker content 1.33 mol% (sample M75).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Institute of Physical ChemistryJohannes Gutenberg-Universität MainzMainzGermany

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