We describe aspects of the rheological behavior in aqueous solution of
three associative polymers with a comb architecture. These polymers o
f identical structure but different molecular weight are based on poly
(ethylene glycol) of M = 8400, joined by a coupling agent bearing a C1
4H29-group. In steady shear, these polymer solutions exhibit a strong
increase in low shear viscosity for concentrations between 1 and 2 wt
%, and a sharp shear thinning transition at a hear rate of ca. 100 Hz.
Some differences are seen between the ''as prepared'' and recrystalli
zed samples. Oscillatory shear and first normal stress difference (N-1
) measurements were carried out on the lowest molecular weight sample,
with an average of three pendant C14H29-groups per chain, and compare
d to the behavior of a telechelic polymer of similar molecular weight
with C16H33-end groups. N-1 measurements on both systems show similar
behavior: a sharp increase in N-1 which persists well into the shear t
hinning domain, followed by a decrease in N-1 as the shear rate is inc
reased further. The decrease in N-1 and the strong shear thinning toge
ther suggest that the networks break down at high shear rates. In osci
llatory shear experiments, major differences between the two types of
polymers are apparent. The comb polymer exhibits a broad distribution
of relaxation times, with a longest relaxation time of ca. 7 s, 2 orde
rs of magnitude longer than that found for the telechelic polymer. Fro
m independent information about micellar structures present in the sys
tem, we calculate the functionality of the networks formed. For a give
n concentration, we find a much higher fraction of bridging chains and
a much lower fraction of looped chains for the comb polymer than for
the corresponding telechelic polymer.