Dynamic mechanical analysis of supercooled water in nanoporous confinement

Authors/others:Soprunyuk, Viktor; Schranz, Wilfried; Huber, Patrick (Technische Universität Hamburg-Harburg (TUHH))
Abstract:Dynamical mechanical analysis (DMA)(f = 0.2-100Hz) is used to study the dynamics of confined water in mesoporous Gelsil (2.6 nm and 5 nm pores) and Vycor (10 nm) in the temperature range from T = 80 K to 300 K. Confining water into nanopores partly suppresses crystallization and allows us to perform measurements of supercooled water below 235 K, i.e., in water's so-called "no man's land", in parts of the pores. Two distinct relaxation peaks are observed in tan delta around T-1 approximate to 145K (P-1) and T-2 approximate to 205 K (P-2) for Gelsil 2.6 nm and Gelsil 5 nm at 0.2 Hz. Both peaks shift to higher T with increasing pore size d and change with f in a systematic way, typical of an Arrhenius behaviour of the corresponding relaxation times. For P-1 we obtain an average activation energy of E-a = 0.47 eV, in good agreement with literature values, suggesting that P-1 corresponds to the glass transition of supercooled water. The observation of a pronounced softening of the Young's modulus around 165 K (for Gelsil 2.6 nm at 0.2 Hz) supports the conjecture of a glass-to-liquid transition in the vicinity of P-1. In addition we find a clear-cut (1/d)-dependence of the calculated glass transition temperatures which extrapolates to T-g(1/d = 0) = 136 K, in agreement with the traditional value of water.
Number of pages:7
Date of publication:8.2016
Journal title:Europhysics Letters
Peer reviewed:true
Digital Object Identifier (DOI):http://dx.doi.org/10.1209/0295-5075/115/46001
Publication Type:Article