Hydrophobically associating polymer hydrolysis effects

Hydrophobic associations can dominate polymer conformation in solution and solution rheological properties. Intrinsic viscosity and Huggins interaction coefficients provided information on the conformation and intramolecular aggregation behavior of these polymers in dilute solution. The presence of hydrophobic associations caused a decrease in the intrinsic viscosity and an increase in the Huggins constant. These effects could be counterbalanced by increasing the ionic charge on the polymer through hydrolysis or by copolymerization with sodium acrylate. 

An important aspect of Figure 39a is that ionic character and hydrophobic interactions have opposite effects on intrinsic viscosity. In the dilute regime, hydrolysis of the associating polymer increases its intrinsic viscosity, whereas increasing the hydrophobic content reduces its intrinsic viscosity. 

One major disadvantage of HPAM is its high sensitivity to salts [41]. This is not so for hydrophobically associating polyacrylamide. Figure 45 shows the effect of salts on the apparent viscosity at 1.3 s for HPAM and hydrolyzed copolymer of N-octylacrylamide/acrylamide. All polymers have the same degree of hydrolysis at 18%. The two associating polymers contained hydrophobe contents of 1 and 1.25 mol%. The addition of hydrophobe reduced the sensitivity to salts, especially at the higher hydrophobe content examined. 

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