FLIM nanoscopy resolves the structure and preferential adsorption in the co-nonsolvency of PNIPAM microgels in methanol-water
Polymer microgels are swollen macromolecular networks with a typical size of hundred of nanometers to several microns that show an extraordinary open and responsive architecture to different external stimuli, being therefore important candidates for nanobiotechnology and nanomedical applications suc...
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| Published in: | Journal of colloid and interface science Vol. 678; no. Pt B; pp. 210 - 220 |
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| Main Authors: | , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
United States
Elsevier Inc
15-01-2025
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| Subjects: | |
| Online Access: | Get full text |
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| Summary: | Polymer microgels are swollen macromolecular networks with a typical size of hundred of nanometers to several microns that show an extraordinary open and responsive architecture to different external stimuli, being therefore important candidates for nanobiotechnology and nanomedical applications such as biocatalysis, sensing and drug delivery. It is therefore crucial to understand the delicate balance of physical-chemical interactions between the polymer backbone and solvent molecules that to a high extent determine their responsivity.
In particular, the co-nonsolvency effect of poly(N-isopropylacrylamide) in aqueous alcohols is highly discussed, and there is a disagreement between molecular dynamics (MD) simulations (from literature) of the preferential adsorption of alcohol on the polymer chains and the values obtained by several empirical methods that mostly probe the bulk solvent properties.
It is our contention that the most efficacious method for addressing this problem requires a nanoscopic method that can be combined with spectroscopy and record fluorescence spectra and super-resolved fluorescence lifetime images of microgels labeled covalently with the solvatochromic dye Nile Red. By employing this approach, we could simultaneously resolve the structure of sub-micron size objects in the swollen and in the collapsed state and estimate the solvent composition inside of them in ▪–▪ mixtures for two very different polymer architectures. We found an outstanding agreement between the MD simulations and our results that estimate a co-solvent molar fraction excess of approximately 3 with a very flat profile in the lateral direction of the microgel.
•STED-FLIM resolves the structure and solvent composition in submicron-sized PNIPAM microgels in methanol-water mixtures.•Our methodology allows us to measure the distribution of protic solvents in complex liquid mixtures without the need of any calibration.•We found an outstanding agreement between our FLIM results and MD simulations (from literature) for the molar fraction excess of methanol. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0021-9797 1095-7103 1095-7103 |
| DOI: | 10.1016/j.jcis.2024.08.235 |