tailieunhanh - INTERFACIAL AND CONFINED WATER Part 5

Mật độ nước trung bình trong lỗ chân lông hình trụ với Rp = 12 là một chức năng của sự tương tác nước tường u0. Đóng hình vuông: giới hạn nước trong lỗ chân lông mở là trong trạng thái cân bằng với số lượng lớn nước bão hòa. | 118 Interfacial and confined water Figure 65 The average water density in cylindrical pores with Rp 12 A as a function of the water-wall interaction Uo. Closed squares confined water in open pore is in equilibrium with saturated bulk water. Open circles confined water in closed pore at the pore coexistence curve. Crossing point of two dependences indicates a critical water-wall interactions which separates regimes of capillary condensation and capillary evaporation. always metastable between the walls with Uo -1 kcal mol. Of course in a wide hydrophobic pores this metastable state may be long lived. With pore narrowing metastable liquid water approaches the stability limit and cavitation becomes unavoidable 383 . In narrow cylindrical pores the liquid-vapor transition is strongly rounded and this results in an intermittent permeation of water through narrow channels 384-386 . This behavior should be attributed to the thermally induced transitions between vapor-like and liquid-like states separated by small energetic barrier 385 . Metastability of liquid water between hydrophobic surfaces 381 387 and or liquid density depletion near these surfaces 388 389 give rise to the long-range attractive forces hydrophobic forces between them. Both metastability of a liquid between weakly attractive surfaces and depletion of a liquid density near a weakly attractive surface are general phenomena and they should be relevant to all fluids. The only peculiar feature of water is abundance of weakly attractive hydrophobic surfaces for water on the Earth. The phenomenon of hydrophobic attraction was extensively studied experimentally 212 . Less is known about the Phase diagram of confined water 119 phenomenon of hydrophilic repulsion 390 which was mainly observed for interactions between soft amphiphilic surfaces in liquid water 391 . Similar to hydrophobic attraction hydrophilic repulsion is not related to peculiar water properties but is a general phenomenon for all fluids between