Abstract
The heat capacity (Cp) of confined polystyrene in particles is investigated in the case of close-packed structure using differential scanning calorimetry (DSC). This confined geometry allows the highest possible free surface area (3/R) in a dense macroscopic sample. We show that Cp of polystyrene increases above that of bulk below bulk glass transition (Tg) T > Tg – 30 °C. Such deviation depends mainly on the fraction of free surface area, which is interpreted by the existence of zone of higher degrees of freedom on the free surface and comfort the previous results of the depression of a volumetric glass transition Tgvol and the higher surface mobility by the photobleaching technique. On the other hand, the main discontinuity of Cp coincides with the bulk glass transition zone Tg, which comforts the finding of the existence of a core with a bulk behavior. The Cp curves exhibit both behaviors observed in confined system: (i) a growth of Cp in the glassy regime which is in agreement with the negative shift ...
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