HIGH-PRESSURE VISCOSITY OF AN ASSOCIATING POLYMER SYSTEM - ZINC SULFONATED POLYSTYRENE POLY(STYRENE-4-VINYLPYRIDINE) COPOLYMER SOLUTION

Measurements made on nonassociating polystyrene-based polymers in tetrahydrofuran, THF, reveal that the intrinsic viscosity [eta], remains virtually constant with increasing pressure from 0 to 20 kbar. An associating polymer system of a 1:1 blend of zinc sulfonated polystyrene and poly(styrene-4-vinylpyridine) copolymer in THF shows a decrease in [eta] not seen in the nonassociating analogues. In addition, the associating system shows an unusual, abrupt, reversible rise in viscosity as pressure is increased to ca. 2 kbar and the viscosity exhibits a slow pressure response (almost-equal-to 30 min equilibrium times) at this pressure, seemingly indicating some type of cooperative effect. We attribute both the pressure-induced decrease of [eta] and this abrupt viscosity rise to pressure-driven changes in the degree of association. We apply the Flory equation to model the high-pressure behavior of [eta] on changing effective molecular weight; we find that, for the 1.0 g/dL system, M(eft) decreases by almost-equal-to 29% from ambient pressure to 10 kbar. The abrupt viscosity rise corresponds to a almost-equal-to 10% increase in M(eft) at 2 kbar. When the concentration is reduced from 1.0 to 0.5 g/dL, the abrupt viscosity rise is eliminated and the decline in the effective molecular weight is diminished.