A composition and method whereby the same group that is attached to or within the backbone of an associative thickener is reversibly switched between being hydrophilic and hydrophobic in nature. When the group that is attached to or within the backbone is rendered hydrophilic, the aqueous thickener is pourable and readily incorporated into aqueous polymer compositions. When this group is rendered hydrophobic, the thickener performs its thickening function efficiently. Switching is readily accomplished by adjusting the pH of the associative thickener composition and the aqueous polymer composition being thickened.