Surface activity of C17-oligo(propylene oxide-b-ethylene oxide)s in the absence and presence of sodium oleate

To improve our understanding of the complex interface features related to deinking in paper recycling, model surfactant systems were investigated. Novel nonionic structures incorporating a C-17 hydrophobic chain and block PO-EO sequences of equal composition but different total length were tested in terms of both their surface activity and their competitive adsorption at the air/water interface with respect to the oleate anion. Static and dynamic measurements provided useful information about the diffusion to and molecular orientation at the interface of these species. In particular, the oligoether portion of the nonionic surfactants played a significant role in these phenomena, thanks to the changes of its chain conformation as a function of the crowding and composition of the interface.