title: Probing Nanoscale Thermal Transport in Surfactant Solutions.
abstract: Surfactant solutions typically feature tunable nanoscale, internal structures. Although rarely utilized, they can be a powerful platform for probing thermal transport in nanoscale domains and across interfaces with nanometer-size radius. Here, we examine the structure and thermal transport in solution of AOT (Dioctyl sodium sulfosuccinate) in n-octane liquids using small-angle neutron scattering, thermal conductivity measurements, and molecular dynamics simulations. We report the first experimental observation of a minimum thermal conductivity occurring at the critical micelle concentration (CMC): the thermal conductivity of the surfactant solution decreases as AOT is added till the onset of micellization but increases as more AOT is added. The decrease of thermal conductivity with AOT loading in solutions in which AOT molecules are dispersed as monomers suggests that even the interfaces between individual oleophobic headgroup of AOT molecules and their surrounding non-polar octane molecules can hinder heat transfer. The increase of thermal conductivity with AOT loading after the onset of micellization indicates that the thermal transport in the core of AOT micelles and across the surfactant-oil interfaces, both of which span only a few nanometers, are efficient.
authors.affiliation: Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA.
authors.forename: Fangyu
authors.initials: F
authors.lastname: Cao
authors.affiliation: Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA.
authors.forename: Jiajun
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
authors.forename: Yadong
authors.initials: Y
authors.lastname: He
authors.affiliation: Center for Neutron Research, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Stop 6102, Gaithersburg, MD 20899 USA.
authors.forename: B
authors.initials: B
authors.lastname: Hammouda
authors.affiliation: Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
authors.forename: Rui
authors.initials: R
authors.lastname: Qiao
authors.affiliation: Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA.
authors.forename: Bao
authors.initials: B
authors.lastname: Yang