The dielectric behavior of cationic, anionic and nonionic polyacrylamide aq
ueous solutions was monitored. The magnitude of dielectric increments of th
e polymer solutions were found to depend upon the type of the dipole and it
s alignment along the chain, pH of the media and the polymer concentration.
The hydrolysis of the amide moieties in the alkaline media was found to af
fect the conformations of the highly charged cationic polyacrylamide by enh
ancing inter-unit interactions between the cationic and carboxylic moieties
. Similarly, the dielectric constant increments of the nonionic polyacrylam
ide were found to become smaller in the alkaline conditions in contrast to
very high values in the acidic conditions. The viscosity behavior showed th
e extended form of conformations in the chains as evidenced by the observed
large reduced viscosities when inter-unit repulsion was dominant and while
the presence of inter-unit attractions in the chain was characterized by s
maller reduced viscosities. A systematic decrease in the intrinsic viscosit
ies of polymer solutions was noted both in acidic as well as alkaline media
with the addition of salt. The isentropic compressibilities of the polymer
solutions under the same conditions showed a declining trend with the incr
easing salt concentrations suggesting the increased compactness of the chai
ns. (C) 1998 Elsevier Science Ltd. All rights reserved.