Phase behaviour of aqueous mixtures of sodium dodecyl sulfate with a weakly cationically charged acrylamide-based copolymer

Abstract

The phase behaviour at constant polymer concentration of aqueous mixtures of sodium dodecyl sulfate (SDS) with a weakly charged cationic polymer (PAM6) based on an acrylamide backbone, containing 6 mol% cationic sites, is presented. Upon increasing the SDS concentration, the known strongly hydrophilic character of the acrylamide polymer turns gradually to moderately hydrophobic. Thus, although at room temperature the aqueous PAM6/SDS mixtures present the expected phase behaviour (fully homogeneous or phase-separated, depending on the polymer/surfactant concentration ratio), they exhibit upon heating either upper critical solution temperature or lower critical solution temperature characteristics.