Water-soluble copolymers. 56. Structure and solvation effects of polyampholytes in drag reduction

Water-soluble polyampholytes based on acrylamide (AM), sodium 2-acrylamido-2-methyl-propanesulfonate (NaAMPS), (2-acrylamido-2-methylpropyl) timethylammonium chloride (AMPTAC), sodium 3-acrylamido-3-methylbutanoate (NaAMB), and 30((2-acrylamido-2-methylpropyl)dimethylammonio)-1-propanesulfonate (AMPDAPS) have been synthesized and characterized. The molecular weights of the polymers range from 1.4 [times] 10[sup 6] to 21.5 [times] 10[sup 6]. Almost all the polyampholytes showed higher intrinsic viscosities at higher solvent ionic strength. The drag reduction behavior of high and low charge density polyampholytes and polybetaines was examined with a rotating-disk rheometer. All the polymers exhibited higher drag reduction at increased solvent ionic strength. The poly(sulfobetaines) (copolymers of AM and AMPDAPS) were found to be the most efficient drag reducers, and the high charge density polyampholyte (copolymer containing 50 mol % each of AMPTAC and NaAMPS) was the least efficient. Experimental data indicate that theoretical models of drag reduction should include parameters for polymer-solvent interactions and molecular associations.