Synthesis and solution properties of amphiphilic cycloterpolymers of 1,1-diallyl-4-formylpiperizinium chloride, diallyloctadecylammonium chloride and sulfur dioxide

The cycloterpolymerizations of hydrophilic monomer (1,1-diallyl-4-formylpiperizinium chloride) with hydrophobic monomer (diallyloctadecylammonium chloride) and sulfur dioxide in dimethyl sulfoxide using azobisisobutyronitrile (AIBN) as the initiator afforded a series of water-soluble monocationic polyelectrolytes (MCPEs) in well over 90% yields. Acidic (HCl) hydrolysis of the N-formyl groups in MCPEs to NH₂⁺Cl^- groups gave the dicationic polyelectrolytes (DCPEs), which on treatment with one equivalent of NaOH furnished the basic cationic polyelectrolytes (BCPEs) containing basic as well as quaternary nitrogens. The solution properties of the resultant series of interconverting polyelectrolytes (MCPE → DCPE ↔ BCPE) were investigated by viscometric techniques. The polymer concentration C*_HA of 0.2 g/dL was required for the manifestation of hydrophobic associations in a MCPE containing 4.5 mol% octadecyl pendents. The DCPEs exhibited sharp increase in viscosity in salt (NaCl)-added solution as compared to salt-free water. The pH-responsive BCPE is shown to demonstrate better associative properties in the absence of HCl; upon addition of HCl, the charge density increases in the polymer chains thereby resulting in increased electrostatic repulsions and decreased associations. Polymer-surfactant interactions were investigated using cationic surfactant cetyltrimethylammonium chloride (CTAC); tremendous increase in the viscosity values of the DCPE was observed in the presence of the surfactant.