화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.122, No.13, 3378-3383, 2018
Molecular-Scale Description of SPAN80 Desorption from a Squalane-Water Interface
Extensive all-atom molecular dynamics calculations on the water-squalane interface for nine different loadings with sorbitan monooleate (SPAN80), at T = 300 K, are analyzed for the surface tension equation of state, desorption free-energy profiles as they depend on loading, and to evaluate escape times for adsorbed SPAN80 into the bulk phases. These results suggest that loading only weakly affects accommodation of a SPAN80 molecule by this squalane water interface. Specifically, the surface tension equation of state is simple through the range of high tension to high loading studied, and the desorption free-energy profiles are weakly dependent on loading here. The perpendicular motion of the centroid of the SPAN80 headgroup ring is well described by a diffusional model near the minimum of the desorption free-energy profile. Lateral diffusional motion is weakly dependent on loading. Escape times evaluated on the basis of a diffusional model and the desorption free energies are 7 x 10(-2) s (into the squalane) and 3 x 10(2) h (into the water). The latter value is consistent with desorption times of related lab-scale experimental work.