A coordinated research program has been initiated with the aim of developing environmentally responsive copolymers for Improved Oil Recovery (lOR). These novel polymer systems possess amphipathic microstructures which allow reversible pH-, salt, shear-, or temperature-responsiveness in aqueous media. Viscosity, fluid flow behavior, polymer interactions with reservoir rock and entrapped oil, and phase behavior can be changed by altering pH or salt concentration or by adjusting flow rates. The objectives of this work are to: synthesize responsive, amphiphilic systems; characterize molecular structure and solution behavior; measure rheological properties of the aqueous fluids including behavior in fixed geometry flow profiles and beds; and to tailor final polymer compositions for in situ rheology control under simulated reservoir conditions. This report focuses on a) synthesis, characterization, and solution studies of pH and salt responsive thickeners and b) development of procedures and an apparatus for measuring extensional flow. Polymers have been prepared from N-vinylformamide (NVF), sodium 3-acrylamido- 3-methylbutanoate (NaAMBA), sodium 2-acrylamido-2-methylpropanesulfonate (NaAMPS), sodium acrylate (NaA), acrylamide (AM), 4-(2-acrylamido-2- methylpropyldimethylammonio)butanoate] ( ABAM series), 3-(2-acrylamido-2- methylpropyldimethylammonio)propanesulfonate (DAPSAM series) and 2-(2- acrylamido-2-methylpropyldimethylammonio) ethanoate (DAEAM series). The hypothesis that polymer coils will only extend when the rate of coil expansion is greater than the rate of recovery was examined and the minimum fluid extension rate was shown to be inversely proportional to the hydrodynamic diameter of the coil. A low shear bob and cone rheometer has been designed in our laboratories for accurate measurement of rheological behavior of aqueous fluids in dilute solutions.