Molecular dynamics study on the liquid-liquid contact angle in liquid-liquid phase separated aerosols

Abstract. The contact angle is a key parameter in describing the morphology of liquid-liquid phase separated (LLPS) aerosols. However, existing experimental methods are unable to precisely measure the contact angle at the nanoscale. Here, molecular dynamics (MD) simulations based on Martini force field and OPLS-UA force field are conducted to reveal the effects of temperature, water content, inorganic salt (NaCl) content and surfactant (suberic acid) content on the liquid-liquid contact angle in water-dodecane LLPS aerosols, and the applicability of classical Young’s equation is analyzed. MD simulations show that the contact angle is positively correlated with temperature and water content but is negatively correlated with NaCl content and suberic acid content. The Martini force field generally results in larger contact angles and stronger influence of NaCl than the OPLS-UA force field. Interfacial tensions of gas-water and water-dodecane calculated based on the OPLS-UA force field are closer to the experimental results. At the nanoscale, the contact angle calculated by Young's equation always deviates significantly from MD simulations, necessitating the inclusion of line tension. Furthermore, reliable line tensions for different systems have been obtained and fitted with a quartic polynomial function.