Synthesis, Surface, Thermodynamic Properties of Some Biodegradable Vanillin-Modified Polyoxyethylene Surfactants

Four water-soluble non-ionic ethoxylated surfactants based on vanillin were synthesized (VE₁₅, VE₂₀, VE₄₀, and VE₆₀). The chemical structures of these surfactants were confirmed using FT-IR and ¹H-NMR spectra. The molecular weights of the compounds were determined using viscosity measurements and gel permeation chromatography. Surface tension as a function of the concentration of the surfactant in aqueous solution was measured at 25, 40 and 55?°C. From these measurements, the critical micelle concentration (CMC), effectiveness (??_cmc), efficiency (pC₂₀), maximum surface (??_max) excess and minimum surface area (A _min), were calculated. The surface activity measurements showed their high tendency towards adsorption and micellization and their good surface tension reduction, and low interfacial tension. The emulsion stability measurements showed the applicability of these surfactants as emulsifying agents. The thermodynamic parameters of micellization (??G _mic, ??H _mic, ??S _mic) and adsorption (??G _ads, ??G _ads, ?S _ads) showed their tendency towards adsorption at the interfaces and also micellization in the bulk of their solutions. The biodegradability of the prepared surfactants was tested in river water using die-away method and showed their readily biodegradation in the open environment.