2023/02/27 by Antonio Rubio-Andrés, Rubio-Andrés, Antonio, Delfi Bastos‐González +3
Materials Science · #Covalent Organic Framework Applications #FOS: Physical sciences #Pickering emulsions and particle stabilization #Polyoxometalates: Synthesis and Applications #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.2302.14010
openalex publication_date 2023/02/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
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 charged pNIPAM microgels with the Keggin-type polyoxometalate Na3PW12O40 (POM). In bulk, we observed charge inversions below and above the volume phase transition temperature (VPTT) at significantly low POM concentrations as 5⋅10-5 M. In the presence of POM, the microgels exhibited a deswelling-swelling-deswelling behaviour below the VPTT, and a two-step further deswelling above the VPTT. When microgels were confined at 2D water/air interfaces, adding 10-5 M of POM below the VPTT was equivalent to heat above the VPTT and compress the monolayer from 5 to 20 \textmN 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 POM 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 POM was characterized by EDS mapping and XPS. The microgel monolayers with POM improved their resistance to plasma etching, which could be useful for soft colloidal lithography.