The dynamics and conformation of the nonionic surfactant NP100 (nonylphenol ethoxylate with an average of 84 oxyethylene units), adsorbed on colloidal silica and on polystyrene latex particles, have been studied by the nuclear magnetic resonance relaxation technique. To obtain specific information about the spin relaxation from the methylene groups situated at the hydroxyl-terminal end of the polyoxyethylene (POE) chain, this part was labeled with deuterium in a two-step synthesis. Spin relaxation studies of the labeled part of the adsorbed surfactant (2H relaxation) suggested that the dynamics was slower in comparison with the spin relaxation of the surfactant in solution. Also, it was seen that the dynamics was slower on the silica surface than on the polystyrene surface. This was in agreement with previous studies on the average proton spin relaxation of the whole POE chain of the surfactant on silica and on polystyrene surfaces. The correlation time constant for the slow motions of the POE chain was calculated to be as large as 7.4 ms for NP100 on the polystyrene particles. Also this was in good agreement with studies made on the exchange dynamics of the surfactant in different dispersions, where it was found that the exchange between the solution and the particles was slow.
- ²H relaxation
- nonylphenol ethoxylate
- nuclear magnetic resonance (NMR)