Thermal Properties of Supercooled Water Confined within Silica Gel Pores

Adiabatic calorimetry of water confined within nano‐pores of silica gel was carried out. The water within pores was classified into two parts, namely interfacial water and internal water. Water within 3 nm pores was well prevented from crystallization, and showed a heat capacity peak at 227 K and two glass transitions at 115 K and 160 K. Meanwhile, in the cases of 6 nm and 50 nm, water showed only one glass transition at 125 K and 132 K, respectively. The glass transition at 160 K and the broad heat capacity peak at 227 K are attributed to the internal water. The interfacial water shows a glass transition at lower temperature than internal water and no heat capacity anomaly at around 227 K. The heat capacity curve of internal water seemed to be connected smoothly with the other data obtained so far, indicating that the properties of the internal water is close to those of bulk water.