13 October 2014 to 7 November 2014
Nordita, Stockholm
Europe/Stockholm timezone

My Personal Thoughts About the Relaxation Behaviour of Supercooled Water

24 Oct 2014, 16:00
1h
FB52 (Nordita, Stockholm)

FB52

Nordita, Stockholm

Speaker

Prof. Jan Swenson (Chalmers University of Technology)

Description

In this presentation I will give my personal thoughts about the calorimetric and relaxation behavior of supercooled bulk water, based mainly on studies of supercooled water and aqueous solutions in confinements. Such studies show that confined water lacks a clear calorimetric glass transition and associated viscosity related structural relaxation process. This finding is in contrast to most other liquids and indicates that the dynamics associated with the glass transition of bulk water involves an exceptionally large volume of cooperatively rearranging regions at temperatures close to the glass transition temperature, Tg, due to the completion of an ice- like tetrahedral network structure close to Tg. In confinements, where ice formation can be prevented, no similar structural relaxation process can occur due to the geometrical restrictions and no Tg is consequently observed. For confined water-glycerol solutions the glass transition and its associated structural relaxation can be observed up to a water concentration of about 90 wt%. At this high water concentration Tg increases (and the structural relaxation slows down) with increasing water content, indicating that the added water has an anti-plasticizing effect on the glycerol molecules at such a high water concentration, due to the rigidity of a nearly tetrahedral hydrogen bonded network structure of water at low temperatures. The results further predict that Tg of bulk water should be located at an unexpectedly high temperature, i.e. at least above 190 K. This further implies that the results from these confinement studies seem to be in conflict with previous results for glassy bulk water. Reasons for this apparent conflict and possible misinterpretations are discussed. Finally, I give my personal thoughts about the possible liquid-liquid transition of supercooled water.

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