THE ENERGETICS OF SURFACTANT ADSORPTION AT THE AIR-WATER INTERFACE.
Abstract
The standard free energy, enthalpy, and entropy changes (G, H, and S, respectively) for the adsorption at the air-water interface of a commercial ethylene oxide (EO) adduct of straight chain nonylphenol from monomer solution at the critical micelle concentration (CMC) were calculated from surface tension-concentration data at 21-45C using the Gibbs equation, the standard free energy change equation G = -RT 1n (interfacial monomer concentration/CMC), and the Gibbs-Helmholtz equation which gave H directly from the slope of the (G/T) vs (1/T) function. The CMC and surface tension at the CMC (gamma-CMC) decreased, and -G and molecular area increased slightly, with increasing temperature. The H and S values were positive, and appear explainable by the postulations applied to micellization. At ambient temperature (28C) an increase in the (EO) mo1 ratio of straight chain nonylphenol and C13 secondary alcohol ethoxylates resulted in increases of CMC, gamma-CMC, and molecular area, and slight decreases in -G. A comparison of the 9(EO) mo1 ratio adducts of C13 straight chain primary and secondary alcohols showed that the CMC and molecular area of the secondary alcohol ethoxylate were larger, and the gamma-CMC and -G smaller, than the corresponding values of the primary alcohol ethoxylate. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1966
- Accession Number
- AD0634317
Entities
People
- A. Mankowich