Recent advances in associating polymers prepared by micellar polymerization

Multisticker polymer chains consisting of polyacrylamides hydrophobically m odified with low amounts of N,N-dihexylacrylamide (HMPAM) have been prepare d by a free radical micellar polymerization technique. The rheological beha vior of semi-dilute solutions of HMPAM with variable molecular weights (M-w approximate to 1.15x10(4) to 2.2x10(6)), hydrophobe contents ([H] = 0.5 to 2 mol%) and hydrophobic block lengths (N-H = 1 to 7 units per block) has b een investigated as a function of polymer concentration (C). Two different regimes can be clearly distinguished in the zero-shear viscosity eta(0) = f (C) curves. A first unentangled regime where the viscosity increase rate st rongly depends on N-H and [H]. A second entangled regime where the viscosit y follows a scaling behavior of the polymer concentration with an exponent close to 4, whatever [H] or N-H In this regime, the results can be quite we ll accounted for by an hindered reptation model.