Water-based latex dispersions.: 2.: Adsorption and dynamics of nonionic surfactants on colloidal particles with different interfacial properties

Studies with the proton nuclear magnetic resonance relaxation technique were carried out on the adsorption on colloidal silica and polystyrene latex dispersions of the nonionic surfactants NP10 and NP100 (poly(ethylene glycol) nonylphenol ether with 10 and 84 oxyethylene groups in mean, respectively) and of poly(ethylene glycol)s (PEGs) of molecular weights 196 and 4120 g/mol. It was found that the larger PEG on silica displayed similar molecular dynamics as compared to the surfactant with 84 oxyethylene groups (NP100) on silica. This suggested that the same relative amounts of trains and loops were present on the polar surface. On the other hand, the PEG4120 on polystyrene showed a more restricted dynamics than the NP100 surfactant adsorbed on the hydrophobic polystyrene surface. The NP10 experienced a high restriction of its dynamics on polystyrene seen as removal of segmental motions, while the PEG196 had a faster dynamic on this surface. The mobility of PEG196 on silica was even higher. Conclusively, the predominant adsorption mechanism on a hydrophobic surface changed from the thermodynamically more favorable situation with contact between the surfactant nonylphenol group and the particle surface to a less favorable contact when oxyethylene segments of the PEG molecules interacted with surface ionic sites.