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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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| 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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| 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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Mundra, Manish K.
in Cooperation with on an Cooperation-Score of 37%
Topics
Publications (3/3 displayed)
- 2006Confinement, composition, and spin-coating effects on the glass transition and stress relaxation of thin films of polystyrene and styrene-containing random copolymerscitations
- 2005Impacts of polystyrene molecular weight and modification to the repeat unit structure on the glass transition-nanoconfinement effect and the cooperativity length scalecitations
- 2005On the glass transition and physical aging in nanoconfined polymers
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article
Impacts of polystyrene molecular weight and modification to the repeat unit structure on the glass transition-nanoconfinement effect and the cooperativity length scale
Abstract
<p>The effect of nanoconfinement on the glass transition temperature (T <sub>g</sub>) of supported polystyrene (PS) films is investigated over a broad molecular weight (MW) range of 5000-3 000 000 g/mol. Polystyrene MW is shown to have no significant impact on the film thickness dependence of T <sub>g</sub> - T <sub>g,bulk</sub>. In contrast, a small modification to the repeat unit structure of PS has a dramatic impact on the T <sub>g</sub>-nanoconfinement effect. The strength of the thickness dependence of T <sub>g</sub> is greater for poly(4-methylstyrene) (P4MS) than for PS and yet much greater for poly(4-tert-butylstyrene) (PTBS). The T <sub>g</sub> reduction for PTBS is 47 K below T <sub>g,bulk</sub> for a 25 nm thick film, with the onset thickness for confinement effects in PTBS being 300-400 nm. Measurements of the size of cooperatively rearranging regions, ξ <sub>CRR</sub>, in bulk polymer systems at T <sub>g</sub> reveal that PS MW has no significant effect on ξ <sub>CRR</sub> unless PS is oligomeric or nearly oligomeric. However, changes to repeat unit structure and diluent addition affect ξ <sub>CRR</sub> values, but not in a manner that yields an obvious correlation with the T <sub>g</sub>-nanoconfinement effect.</p>