| Autor: |
Kunz, Simon, Pawlik, Maria, Schärtl, Wolfgang, Seiffert, Sebastian |
| Předmět: |
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| Zdroj: |
Colloid & Polymer Science; Aug2018, Vol. 296 Issue 8, p1341-1352, 12p |
| Abstrakt: |
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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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