Viscoelastic Properties of Immiscible Telechelic Polymer Blends: Effect of Acid-Base Interactions

When a telechelic polyisoprene (PIP) end-capped with tertiary amine groups is blended with an immiscible telechelic polystyrene (PS) terminated with either sulfonic or carboxylic acid functions, a proton transfer occurs from the acid to the amine end groups. Viscoelastic properties of these blends support the formation of either ammonium sulfonate or ammonium carboxylate linkages between PS and PIP in a manner analogous to block copolymerization. Due to the low stability of ammonium carboxylates, the related polyblends have been investigated up to 100 °C and they show Tg of each polymeric partner. When PS and PIP chain ends are associated through more thermally stable ammonium sulfonates, the thermal dependences of storage and loss shear moduli show two additional relaxation processes at least in some range of PSand PIP molecular weights. By analogy with SAXS analysis of similar polyblends, these relaxations have been assigned to a classic order-disorder transition similar to that seen in traditional block copolymers and to the irreversible dissociation of the sulfonate salts at higher temperatures, respectively. These additional transitions which involve a change in phase morphology have been confirmed by the “Cole-Cole” log G″ vs log G′ plots. © 1992, American Chemical Society. All rights reserved.