STUDIES ON DETERMINATION OF MOLECULAR-WEIGHT FOR ULTRAHIGH MOLECULAR-WEIGHT PARTIALLY HYDROLYZED POLYACRYLAMIDE

The molecular weight characterization of partially hydrolyzed polyacry lamide (HPAM) for enhanced oil recovery use is rather difficult becaus e of its ultrahigh molecular weight copolymer and polyelectrolyte beha viors in solution. In this work the effects of aqueous NaCl solution c oncentration and degree of hydrolysis of polymer on molecular dimensio n were studied. A simple and precise method for determining molecular weight of HPAM is presented. The molecular weight of HPAM with any deg ree of hydrolysis can be calculated from the [eta] - M(w) equation of unhydrolyzed PAM in an H2O system by measuring [eta](Cs-->infinity), o f HPAM obtained in aqueous NaCl solutions by extrapolating salt concen tration to infinity. Because the values of [eta](Cs-->infinity) Of HPA M of different degrees of hydrolysis are all equal to the correspondin g [eta] value of the unhydrolyzed PAM of the same degree of polymeriza tion, the molecular weight of HPAM of any degree of hydrolysis can thu s be calculated from the [eta] - M(w) equation for PAM homopolymer. (C ) 1996 John Wiley & Sons, Inc.