Use of isothermal titration microcalorimetry to monitor the adsorption/desorption processes of sodium dodecyl sulfate with neutral polymers

The optimization of neutral polymer/anionic surfactant mixtures is a critical process in the development of such systems for many various applications. In this report, we describe how systematic isothermal titration microcalorimetry experiments may be designed in such a way that both the adsorption and desorption processes of sodium dodecyl sulfate with two neutral polymers, PAPR* (a copolymer of N-(vinylacryloyl)pyrrolidine containing a covalently bonded 4-vinylpyridine dicyanomethylide chromophore) and PVP (poly(N-vinylpyrrolidone)), can be directly monitored. The desorption of bound SDS from the polymers is achieved using the nonionic surfactant hexaethylene glycol mono-n-dodecyl ether and the possible mechanism via which this process takes place is qualitatively discussed. Finally, one of the beneficial outcomes stemming from this work is that different stable combinations of polymer or polymer/surfactant complex with mixed micelles and monomer surfactant can be formulated.