Greasy Cations Bind to Neutral Macromolecules in Aqueous Solution.

Ions influence the solution properties of macromolecules. Although much is known about anions, cationic effects are considered mostly in terms of weak interactions or exclusion from neutral interfaces. Herein, we have systematically studied the effect of quaternary tetraalkylammonium cations (NH, NMe, NEt, NPr, NBu) on the phase transition of poly(-isopropylacrylamide) (PNIPAM) in aqueous solution.