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Hydrogen Bond Induced Nonmonotonic Composition Behavior of the Glass Transition in Aqueous Binary Mixtures

Johan Sjöström (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Johan Mattsson (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Rikard Bergman (Institutionen för teknisk fysik, Kondenserade materiens fysik) ; Jan Swenson (Institutionen för teknisk fysik, Kondenserade materiens fysik)
Journal of Physical Chemistry B (1520-6106). Vol. 115 (2011), 33, p. 10013-10017.
[Artikel, refereegranskad vetenskaplig]

The glass transition temperature, T(g), of a binary mixture commonly varies monotonically between the T(g)s of its two components. However, mixtures of strongly associating liquids can instead exhibit a nonmonotonic T(g) variation. The origins of such nonideal mixing behavior have often been correlated with composition dependent structural variations. For binary mixtures between a hydrogen- (H-) bonded liquid and water, however, such behavior is generally not well understood. The ubiquity and importance of aqueous mixtures both in nature and in man-made applications stresses the needed for a better understanding. We here demonstrate nonmonotonic T(g) variations in binary mixtures of n-propylene glycol monomethyl ethers (nPGMEs) and water, where the composition dependent T(g) show maxima within an intermediate composition range. We show that these T(g) maxima correspond to crossovers in the composition dependence of the step amplitude in the isobaric heat capacity at T(g). We further demonstrate that the observed effects are caused by H-bond interactions involving the nPGME hydroxyl group. We can account for our obervations using a simple model based on two effects due to the added water: (i) an H-bond induced formation of effective relaxing entities and (ii) a plasticizing effect at high water contents.

Nyckelord: liquid transition, water solutions, relaxation, temperature, dynamics, alcohols, entropy, former, vapor, estrelski sj, 1993, v65, p661

Denna post skapades 2011-09-29. Senast ändrad 2017-10-03.
CPL Pubid: 146697


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Institutionen för teknisk fysik, Kondenserade materiens fysik (1900-2015)



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