Solvent-polymer interaction: I. Molecular transport of some selected organic liquids in polymer membrane

Abstract

Methods and microtechniques for determining solubility, diffusivity, thermodynamic properties, and kinetic parameters of 12 selected organic liquid solvents in polyurethane membrane by thermogravimetry (TG) are described. TG provides a simple, sensitive, rapid, and accurate microtechnique for measuring a minute change in weight (or mass) of a substance as a function of time at isothermal condition or as a function of temperature at dynamic manner. Thus from a single isothermal TG-desorption experiment, solubility and diffusivity of solvent molecules in polyurethane membrane were obtained simultaneously. Furthermore, by a dynamic TG-desorption run, kinetic parameter such as activation energy of desorption of solvent molecules from polyurethane membrane was determined. In addition, much other useful information such as equilibrium sorption constant, the changes in standard enthalpy and standard entropy of sorption, permeability, the activation energy of diffusion and so forth for solvents in polyurethane membrane are also evaluated and discussed. Finally, the correlation between the microscopic molecular structure and macroscopic properties of solvent molecules in polymer membrane is interpreted in terms of linear free energy relationships.