Interactions between Sodium Dodecyl Sulfate and Hydrophobically Modified Poly(acrylamide)s Studied by Electron Spin Resonance and Transmission Electron Microscopy

Abstract

The interactions of hydrophobically modified poly(acrylamide)s (HMPAM) and unmodified poly(acrylamide) (PAM) with sodium dodecyl sulfate (SDS) have been studied by electron spin resonance using 2,2,6,6-tetramethylpiperidine-1-oxyl and 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl as spin probes. The morphologies of dried solutions of the polymers with and without SDS have also been observed by transmission electron microscopy. The rotational correlation time τc of the spin probes reflects the microenvironment of the polymer−micelle aggregates, which indicates that the higher hydrophobicity of HMPAMs leads to a much more compact packing in the polymer−micelle aggregates. The interactions between surfactants and polymers cause morphological transitions of polymers, which results in the polymer chains stretching out.