Synthesis, viscosity behavior, and interactions with a surfactant of some amphiphilic copolymers of diallyldimethylammonium chloride and diallyldodecyl- or diallyloctadecyl-ammonium chloride

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 C₁₈ pendents. This is a notable improvement over the C*_HA values (ca. 15-17 g/dL) for the associating polymers having a ∼ C₁₀ - C₁₄ pendents. At a shear rate of 0.36 s^-1 at 30°C, salt-free water solutions of the CPEs (4 g/dL) containing 8 mol % of the C₁₂ hydrophobes and 3.6, 7.6, 15.5 mol % of C₁₈ 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 C₁₈ 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°C.