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Título: | Free volume in a PVME polymer–water solution |
Autor: | Capponi, Sara; Álvarez González, Fernando CSIC ORCID; Račko, Dušan | Fecha de publicación: | 2020 | Editor: | American Chemical Society | Citación: | Macromolecules 53(12): 4770–4782 (2020) | Resumen: | Molecular dynamics simulations of poly(vinyl methyl ether) in aqueous solution with weight concentration cw = 30% were performed in a wide temperature range by simulated cooling between 400 and 175 K. A shift of glass transition temperature due to plasticization effect is observed with the decrease of simulated TgMD by 25 K as compared to pure PVME at the same simulated cooling rate. The free volume is computed by using different probe radii (Rp). The free volume computed with Rp = 0.5 Å reproduces free volume amounts at the glass transition temperature from the free volume theories as well as thermal expansivity of the excess free volume given as αL – αG. A portion of 90% of the free volume is formed by molecular bodies of both polymer and water molecules. In the presence of water molecules, the free volume of polymer ends shows only a miniscule increase by 7% as compared to the free volume around main-chain monomer units. The free volume around hydrophilic polymer groups involved in hydrogen-bonding formation is decreased, in agreement with the predicted relation between mobility and free volume. A picture hinting why percolation of the free volume is naturally connected with glass transition temperature is provided. By using the computed free volumes, we predicted a value of the orthopositronium (o-Ps) lifetime in the structure to be τ3 = 1.31 ns (40.1 ± 0.5 Å3) in cavities formed solely by monomer units, and τ3 = 2.03 ns for the average cavity in the structure. | Versión del editor: | https://doi.org/10.1021/acs.macromol.0c00472 | URI: | http://hdl.handle.net/10261/218380 | DOI: | 10.1021/acs.macromol.0c00472 | ISSN: | 0024-9297 | E-ISSN: | 1520-5835 |
Aparece en las colecciones: | (CFM) Artículos |
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