PREFERENTIAL ADSORPTION AND VISCOMETRIC BEHAVIOR OF POLY(2-ACRYLAMIDO-2-METHYL PROPANE SULFONAMIDE) IN FORMAMIDE WATER MIXTURES

Specific refractive index increments have been measured for solutions of a new, neutral, water-soluble polymer, poly(2-acrylamido-2-methyl propane sulphonamide) (PASAM), in binary solvents of formamide/water over the whole range of solvent composition. Comparison of these increments with those obtained at constant chemical potential of low molecular weight species yielded the coefficient of selective adsorption (gamma1) of formamide by the polymer. Positive values of gamma1 were exhibited at solvent composition up to 65% (v/v) of the thermodynamically better solvent, formamide. At higher contents of formamide in the binary solvent, formamide is selectively desorbed. The intrinsic viscosities [eta] of PASAM in formamide and in the binary solvents all exceed the value of [eta] in water. The maximum value of [eta] obtains when there is no selective adsorption, i.e. in the solvent containing ca 65% (v/v) of formamide. The validity of the very high value of the solubility parameter of PASAM estimated viscometrically is discussed.