Investigation of the association in water of sodium dodecyl sulfate with a positively charged copolymer based on N-isopropylacrylamide

The interactions of sodium dodecyl sulfate with a positively charged copolymer based on N-iso-propylacrylamide (NIPAM) have been investigated in aqueous solution by turbidimetric and viscometric measurements. The copolymer contains mainly NIPAM and only 5 mol % of the charged comonomer [3 -(methacryloylamino)propyl]-dimethyloctylammonium bromide. The polymer-surfactant complex is insoluble for mixture compositions near to the charge stoichiometry, while it exhibits lower critical solution temperature behavior for mixtures with an excess of polymer or surfactant. In the case of surfactant excess, the transition from an expanded coil to a globular state upon heating has been observed by viscometry.