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arXiv · 1710.02845

Swelling of responsive-microgels: experiments versus models

Valentina Nigro·Roberta Angelini·Monica Bertoldo·Barbara Ruzicka
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Abstract

Interpenetrated Polymer Network (IPN) microgels of PNIPAM and PAAc have been investigated and the experimental data have been compared with theoretical models from the Flory-Rehner theory. We confirm that the swelling behavior of PNIPAM microgels is well described by this theory by considering the second order approximation for the volume fraction $\phi$ dependence of the Flory parameter $\chi(\phi)$. Indeed the Volume-Phase Transition (VPT) of the PNIPAM-PAAc IPN microgel at neutral conditions and in D$_2$O solvents can be well described only considering a third-order approximation. Interestingly we empirically find that sharper is the transition higher is the order of the $\chi(\phi)$ relation which has to be considered. Moreover the VPT can be experimentally controlled by tuning the polymer/solvent interactions through pH and solvent allowing to directly modify the delicate balance between energetic and entropic contributions and to explore the swelling behavior in a wide range of environmental conditions. In particular we find that the most advantageous condition for swelling is in water at acidic pH.

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Valentina Nigro, Roberta Angelini, Monica Bertoldo, Barbara Ruzicka. 2017-10-08. Swelling of responsive-microgels: experiments versus models. https://doi.org/10.1016/j.colsurfa.2017.04.059

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