Solubility of alcohols in ethylene-vinyl alcohol copolymers by inverse gas chromatography

Sorption isotherms of alcohols in EVOH copolymers were determined by inverse gas chromatography below and above the glass transition temperature. The sorbates studied were: methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, and t-butanol. From the sorption isotherms, Henry's law solubility coefficients (S) were evaluated and correlated to size, condensability, and (SINGLE BOND)OH position in the molecule as well as on temperature. Molecular dimension was an important factor, affecting the solubility via two contrary effects: molecular size and condensability. When comparing alcohols of the same size, primary alcohols were sorbed more than secondary alcohols and these more than tertiary alcohols at every temperature in the study. At low temperatures, the larger the size the greater the solubility, contrary to what was observed at high temperatures. Temperature effect on solubility was also tested applying Van't Hoff's equation. Since S behaved differently below and above T_g for every sorbate two values of the enthalpy of solution were obtained, positive above T_g and negative below T_g. © 1996 John Wiley & Sons, Inc.