Vapor pressure osmometry, volumetry and conductometry investigations on the interaction of sodium dodecyl sulfate with poly(ethylene glycol) and poly(propylene glycol) in aqueous solutions

Micellar and thermodynamic properties of sodium dodecyl sulfate (SDS) in aqueous solutions of polyethylene glycol (PEG) (Mw = 400, 2000, 6000 and 10,000 g mol−1) and polypropylene glycol (PPG) (Mw = 400 g mol−1) were determined employing vapor pressure osmometry (VPO), volumetry, compressibility and conductometry techniques at different temperatures. The binding of SDS in aqueous solution with PEG and PPG was investigated by comparison of the thermodynamic properties of aqueous solutions of SDS in the absence and presence of PEG and PPG. In aqueous solutions, SDS does not bind to PEG400 chains however it binds to PPG400, PEG2000, PEG6000 and PEG10000 chains. The plots of water activity, specific conductivity, sound velocity and isentropic compressibility against surfactant concentration for aqueous SDS + polymer (PPG400, PEG2000, PEG6000 and PEG10000) solutions show two break-points: critical aggregation concentration (CAC) and polymer saturation point (C2).