Tuning the bulk behavior and 2D interfacial self-assembly of microgels by keggin-type polyoxometalate ionic specificity Rubio Andrés, Antonio Bastos González, Delfina María Fernández Rodríguez, Miguel Ángel Microgels Keggin-type polyoxometalates Interface Ion specificity Self-assembly Soft colloidal lithography Funding for open access charge: Universidad de Granada / CBUA. We acknowledge Dr. María Tirado Miranda for providing measurements and helpful insight regarding the DLS technique, and Dr. Jordi Faraudo Gener and Dr. Carlos Drummond for insightful conversations, the CIC from University of Granada for the STEM-HAADF and EDS measurements, and the SCAI from the University of Málaga for the XPS measurements. This work was supported by the projects PID2020-116615RA-I00 funded by MCIN/AEI/ 10.13039/501100011033, and EMERGIA grant with reference EMC21_00008, and projects PY20-00241, A-FQM-90-UGR20 funded by Consejería de Universidad, Investigación e Innovación de la Junta de Andalucía, and by FEDER “ERDF A way of making Europe”. Finding new ways to tune the behavior of thermoresponsive microgels in bulk and confined at 2D liquid interfaces is key to achieve a deeper understanding and control of these smart materials. We studied the interaction of positively and negatively charged pNIPAM microgels with the Keggin-type polyoxometalates Na3PW12O40 (POM3−) and H4SiW12O40 (POM4−). In bulk, we observed charge inversions of the positively charged microgels below and above the volume phase transition temperature (VPTT) at significantly low POM concentrations as 5 ⋅ 10−5 M. In the presence of POM, both microgels exhibited a deswelling-swelling-deswelling behavior below the VPTT, and a two-step further deswelling above the VPTT for the positively charged microgels. When the later were confined at 2D water/air interfaces, adding 10−5 M of POM3− below the VPTT was equivalent to heating above the VPTT and compressing the monolayer from 5 to 20 mN m−1. Above the VPTT, the diameter at the interface did not change while the portion immersed in the subphase further deswelled, in agreement with the behavior in bulk. Adding more POM3− did not change the diameter at the interface nor the height of the microgels, showing a saturation effect in 2D. The restructuring of the pNIPAM polymeric network by the POM3− was characterized by EDS mapping and XPS. The microgel monolayers with POM3− improved their resistance to plasma etching, which could be useful for soft colloidal lithography. 2024-04-02T07:31:28Z 2024-04-02T07:31:28Z 2024-04-15 journal article Rubio-Andrés, D. Bastos-González and M.A. Fernandez-Rodriguez. Tuning the bulk behavior and 2D interfacial self-assembly of microgels by keggin-type polyoxometalate ionic specificity. Journal of Molecular Liquids 400 (2024) 124496 2A. https://doi.org/10.1016/j.molliq.2024.124496 https://hdl.handle.net/10481/90290 eng http://creativecommons.org/licenses/by-sa/4.0/ open access Atribución-CompartirIgual 4.0 Internacional Elsevier