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Naji, M. |
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Motta, Antonella |
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Aletan, Dirar |
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Mohamed, Tarek |
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Ertürk, Emre |
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Taccardi, Nicola |
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Kononenko, Denys |
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Petrov, R. H. | Madrid |
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Alshaaer, Mazen | Brussels |
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Bih, L. |
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Casati, R. |
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Muller, Hermance |
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Kočí, Jan | Prague |
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Kalteremidou, Kalliopi-Artemi | Brussels |
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Azam, Siraj |
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Ospanova, Alyiya |
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Blanpain, Bart |
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Ali, M. A. |
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Popa, V. |
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Rančić, M. |
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Ollier, Nadège |
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Azevedo, Nuno Monteiro |
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Landes, Michael |
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Rignanese, Gian-Marco |
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Rittigstein, Perla
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document
On the glass transition and physical aging in nanoconfined polymers
Abstract
<p>The glass transition temperature (T<sub>g</sub>) and physical aging behavior of nanoconfined polymer films were investigated by novel fluorescence methods. These studies have revealed that there are large modifications in both T<sub>g</sub> and physical aging behavior due to interfacial effects. For example, T<sub>g</sub> was observed to decrease compared to bulk in polymers where free-surface effects dominate (e.g., for polystyrene (PS) on silica substrates), while T<sub>g</sub> was observed to increase compared to bulk for polymers where strong attractive substrate interactions dominate (e.g., for poly(2-vinylpyridine) (P2VP) on silica substrates). Similar interfacial effects were observed for physical aging, where attractive substrate effects retarded physical aging compared to bulk. Furthermore, the T<sub>g</sub>-nanoconfinement effect was observed to be widely tunable by small variations on the repeat unit structure of PS or by the addition of low molecular weight diluents or plasticizers. Finally, T<sub>g</sub> and enthalpy relaxation behavior were investigated by differential scanning calorimetry for PS-silica and P2VP-silica nanocomposites. As in the nanoconfined film studies, interfacial interactions were key in dictating the ultimate properties of the nanocomposite, but it was also observed that preparation method plays a significant role.</p>