Why is there no clear glass transition of confined water?
Artikel i vetenskaplig tidskrift, 2013
To overcome the problem of crystallization of supercooled bulk water and water rich solutions we have studied water-glycerol mixtures confined in 21 angstrom pores of the silica matrix MCM-41 C10. The results from the differential scanning calorimetry (DSC) measurements shows an almost concentration independent glass transition temperature, T-g, at about 176 K for water concentrations up to 80 wt%, suggesting that the confined water has no influence on T-g in this concentration range. Rather, the findings indicate that the water molecules in the solutions have a stronger preference to coordinate to the hydroxyl surface groups than the glycerol molecules, which results in a micro-phase separation of the two liquids. The water phase does not give any sign of a T-g and therefore the observed T-g should be associated with the glass transition of the glycerol phase. Finally, we discuss why the confined water does not exhibit any clear calorimetric T-g. (C) 2012 Elsevier B. V. All rights reserved.
Differential scanning calorimetry