The copolymerization of hydrophobic monomers, diallyldodecyl- or diallyloctadecyl-ammonium chloride, with hydrophilic monomer diallyldimethylammonium chloride in dimethyl sulfoxide using azobisisobutyronitrile (AIBN) as the initiator afforded a series of water-soluble cationic polyelectrolytes (CPE) containing various proportions (0-16 mol %) of the hydrophobes. A polymer concentration (C*(HA)) of 0.5 g/dL was required for the manifestation of hydrophobic associations in some of these copolymers containing the C-18 pendents. This is a notable improvement over the C*(HA) values (ca. 15-17 g/dL) for the associating polymers having a similar to C-10 - C-14 pendents. At a shear rate of 0.36 s(-1) at 30 degrees C, salt-free water solutions of the CPEs (4 g/ dL) containing 8 mol % of the C-12 hydrophobes and 3.6, 7.6, 15.5 mol % of C-18 hydrophobe have apparent viscosity values of 780, 6000, 956,000, and 1,100,000 cps, respectively. Considerable increase in the viscosity values of the CPE was observed in the presence of the surfactant cetyltrimethylammonium bromide (CTAB). The superior viscosity behavior for the polymers containing the C-18 hydrophobe in comparison with C-12 is attributed to the longer pendent-length of the former hydrophobe, which can efficiently undergo association from a distance far enough that minimizes interchain repulsion between the like charges. The CPEs containing the hydrophobes were found to be a better inhibitor of the corrosion of mild steel in 1M HCl at 60 degrees C. (C) 2008 Wiley Periodicals, Inc.