Investigation on the interaction of sodium dodecyl sulfate with poly(ethylene oxide) by electron spin resonance and UV spectrum

ESR and UV spectrum of the aqueous solution of sodium dodecyl sulfate(SDS)/poly(ethylene oxide) (PEO) were measured at room temperature respectively, the concentration of PEO was 0. 5% (mass fraction), and the concentration of SDS (m(SDS)) was up to 50 mmol . kg(-1). 2, 4-dinitrophylhydrazone of 2, 2, 6, 6-tetramethyl-4- piperidine-1-oxyl (Tempone-DMPH) was synthesized and used as ESR probe. The binding site of SDS-PEO interaction, the micropolarity and microviscosity information of the microenvironments have been determined by ESR. UV spectrum gives information on the environment of 2, 4-dinitrophylhydrazone group. The hyperfine coupling constant and the rotational correlation time of the spin probe reflect the microenvironment of the polymer-micelle aggregates. The micropolarity of the solutions decreases with increasing SDS concentration, the polymer-micelle aggregate forms a more compact structure at the binding site and the binding site between PEO and SDS micelles yields a strong increase of the microviscosity at the micelle-polymer interface. Spin probe is located near the surface of the micelle. 2, 4- dinitrophylhydrazone group may be adjacent to the sulphate groups, and the nitroxide group penetrates a small distance into the hydrocarbon core of the micelle. The critical aggregation concentration (CAC) and polymer saturation point (PSP) of SDS-0. 5 % PEO at room temperature are approximately 4 and 28 mmol . kg(-1), respectively.