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Issue 19, 2012
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T g depression and invariant segmental dynamics in polystyrene thin films

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Abstract

We investigate the segmental dynamics and glass transition temperature (Tg) of polystyrene (PS) thin films. The former is investigated by alternating current (AC) calorimetry and dielectric spectroscopy (BDS). The Tg, underlying the equilibrium to out-of-equilibrium crossover from the supercooled liquid to the glass, is obtained by differential scanning calorimetry (DSC) and capacitive dilatometry (CD). We show that the intrinsic molecular dynamics of PS are independent of the film thickness both for the freestanding and supported films, whereas Tg decreases with film thickness from several microns down to 15 nm. This result is found for complementary methods and in a simultaneous measurement in BDS and CD. This questions the widespread notion that segmental mobility and the equilibrium to out-of-equilibrium transition are, under any experimental conditions, fully interrelated. For thin films, it appears that the molecular mobility and Tg are affected differently by geometrical factors.

Graphical abstract: T g depression and invariant segmental dynamics in polystyrene thin films

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Publication details

The article was received on 23 Feb 2012, accepted on 26 Mar 2012 and first published on 04 Apr 2012


Article type: Communication
DOI: 10.1039/C2SM25419K
Citation: Soft Matter, 2012,8, 5119-5122
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    T g depression and invariant segmental dynamics in polystyrene thin films

    V. M. Boucher, D. Cangialosi, H. Yin, A. Schönhals, A. Alegría and J. Colmenero, Soft Matter, 2012, 8, 5119
    DOI: 10.1039/C2SM25419K

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