Proton magnetic resonance investigations of nonionic polyoxyethylene nonylphenol surfactant aggregates in nonpolar solvents

Abstract

¹ H n.m.r. chemical shifts of polyoxyethylene(1.5) nonylphenol (Igepal CO–210); polyoxyethylene (4) nonylphenol (Igepal CO–430); polyoxyethylene(5) nonylphenol (Igepal CO–520); polyoxyethylene(6) nonylphenol (Igepal CO–530); polyoxyethylene(9) nonylphenol (Igepal CO–630); polyoxyethylene(10-11) nonylphenol (Igepal CO–710); and polyoxyethylene(15) nonylphenol (Igepal CO–730) in CDCl₃ and those of Igepal CO–530 in CH₂Cl₂, CCl₄, C₆H₆ and C₆D₁₂ have been determined as functions of the stoichiometric surfactant concentration. The data are best fitted in terms of a monomer [graphic omitted] i-mer type association, assuming K₁=K₂=K₃…=K_i. Based on this model percentages of dimers, trimers and of higher aggregates have been calculated at several stoichiometric surfactant concentrations. Percentages of monomers decrease at the expense of predominantly dimers and of small amounts of trimers and higher aggregates with increasing concentrations of surfactant. In CDCl₃ the association is most prominent for Igepal CO–710. Aggregation is considerably more pronounced in C₆H₆ and C₆D₁₂ than in CDCl₃, CH₂Cl₂ or CCl₄. Addition of water hinders the dimerization. Structures of the aggregates are discussed.