Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels.
Two-step deswelling in the Volume Phase Transition of thermoresponsive microgels.
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DOI：
10.1073/pnas.2109560118
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发表时间：
2021-09-14
影响因子：
11.1
通讯作者：
Zaccarelli E
中科院分区：
文献类型：
--
作者：
Del Monte G;Truzzolillo D;Camerin F;Ninarello A;Chauveau E;Tavagnacco L;Gnan N;Rovigatti L;Sennato S;Zaccarelli E
Microgels, colloidal-scale polymer networks, are the prototype soft colloids. When the constituent polymers are thermoresponsive, they undergo a volume phase transition (VPT) from a swollen to a collapsed state at a characteristic temperature, close to ambient one, of great appeal for several applications. To describe this phenomenon, microgels are usually treated as neutral, but here we show that electrostatics needs to be taken into account. In particular, deswelling occurs via a two-step, rather than a homogeneous, particle collapse, mainly driven by peripheral charges located on the microgel corona, for which we also establish a unifying framework encompassing all studied microgels. Our work thus provides a change of perspective to describe these fascinating systems. Thermoresponsive microgels are one of the most investigated types of soft colloids, thanks to their ability to undergo a Volume Phase Transition (VPT) close to ambient temperature. However, this fundamental phenomenon still lacks a detailed microscopic understanding, particularly regarding the presence and the role of charges in the deswelling process. This is particularly important for the widely used poly(N-isopropylacrylamide)–based microgels, where the constituent monomers are neutral but charged groups arise due to the initiator molecules used in the synthesis. Here, we address this point combining experiments with state-of-the-art simulations to show that the microgel collapse does not happen in a homogeneous fashion, but through a two-step mechanism, entirely attributable to electrostatic effects. The signature of this phenomenon is the emergence of a minimum in the ratio between gyration and hydrodynamic radii at the VPT. Thanks to simulations of microgels with different cross-linker concentrations, charge contents, and charge distributions, we provide evidence that peripheral charges arising from the synthesis are responsible for this behavior and we further build a universal master curve able to predict the two-step deswelling. Our results have direct relevance on fundamental soft condensed matter science and on applications where microgels are involved, ranging from materials to biomedical technologies.
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影响因子：
13.6
作者：
Conley GM;Aebischer P;Nöjd S;Schurtenberger P;Scheffold F
通讯作者：
Scheffold F
影响因子：
3.4
作者：
Del Monte, Giovanni;Ninarello, Andrea;Zaccarelli, Emanuela
通讯作者：
Zaccarelli, Emanuela
影响因子：
15.6
作者：
Angel Fernandez-Rodriguez, Miguel;Martin-Molina, Alberto;Maldonado-Valderrama, Julia
通讯作者：
Maldonado-Valderrama, Julia
影响因子：
12.5
作者：
Camerin, Fabrizio;Gnan, Nicoletta;Zaccarelli, Emanuela
通讯作者：
Zaccarelli, Emanuela
影响因子：
4.4
作者：
Deserno, M;Holm, C
通讯作者：
Holm, C