title: Viscoelastic properties of isomeric alkylglucoside surfactants studied by surface light scattering.
abstract: Surface light scattering (SLS) by capillary waves was used to investigate the adsorption behavior of non-ionic sugar surfactants at the air/liquid interface. SLS by the subphase (water) followed predictions from hydrodynamic theory. The viscoelastic properties (surface elasticity and surface viscosity) of monolayers formed by octyl beta-glucoside, octyl alpha-glucoside, and 2-ethylhexyl alpha-glucoside surfactants were quantified at submicellar concentrations. It is further concluded that a diffusional relaxation model describes the observed trends in high-frequency, nonintrusive laser light scattering experiments. The interfacial diffusion coefficients that resulted from fitting this diffusional relaxation model to surface elasticity values obtained with SLS reflect the molecular dynamics of the subphase near the interface. However, differences from the theoretical predictions indicate the existence of effects not accounted for such as thermal convection, molecular rearrangements, and other relaxation mechanisms within the monolayer. Our results demonstrate important differences in molecular packing at the air-water interface for the studied isomeric surfactants.
authors.affiliation: Forest Biomaterials Laboratory, College of Natural Resources, North Carolina State University, Box 8005, Raleigh, North Carolina 27695, USA. ojrojas@ncsu.edu
authors.forename: Orlando J
authors.initials: OJ
authors.lastname: Rojas
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Neuman
authors.forename: Per M
authors.initials: PM
authors.lastname: Claesson
mesh_terms: D000327:Adsorption; D005960:Glucosides / Q000737:chemistry*; D007536:Isomerism; D008027:Light; D012542:Scattering, Radiation; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D014783:Viscosity
chemical_list: D005960:Glucosides; D013501:Surface-Active Agents