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…=Ki. 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.