Stress relaxation and reconstruction of the associating network in semidilute aqueous solutions of hydrophobically modified random block copolymers

We study the transient rheological behavior of associating polyacrylamide-based copolymers in aqueous solution. We measure the characteristic times associated with the stress relaxation after a shear step and with the reconstruction of the transient associating network after its destruction by the shear. These characteristic times differ by 2-4 orders of magnitude depending on the applied shear rate. The stress relaxation is rapidly dominated by the free chains and the small clusters arising from the destruction of the associating network. The latter is related to a large-scale texture that needs very long times (up to 4 x 10(4) s) to re-form after its destruction by the shear.