Comparison Study of the Acrylamide−Water and Polyacrylamide−Water Systems:  Differential Heat Effects, Kinetics, and Mechanisms of Drying and Vapor-Phase Wetting

Differential data on the thermodynamics and kinetics of water-vapor sorption and desorption in the acrylamide−water system at room temperature and 0 < n < 74 ( n is the number of sorbed water molecules per amido group) are obtained. Water-vapor sorption from air of 100% humidity appears to be limitless. The magnitude of the differential molar enthalpy of sorption is about 25 kJ/mol for n ≪ 1, passes through a maximum of 42 kJ/mol in the vicinity of n = 1 and a minimum of 24 kJ/mol in the vicinity of n = 2, and then approaches the level of the heat of water-vapor condensation on the pure water surface. The probability for a water molecule to desorb from the system into vacuum per unit time is observed to monotonically increase with n up to n = 44, with a small minimum for n = 15−17. In the system, a slight tendency for clathratization reveals itself in nonmonotonic dependences of Δ H ( n ) and P ( n ), but no stable clathratization, as such, is identified. The results are compared with the corresponding data for the polyacrylamide−water system. The mechanisms of the sorption−desorption process are discussed.