Amorphous phase state diagrams and viscosity of ternary aqueous organic/organic and inorganic/organic mixtures

Abstract

A Dimer Coagulation, Isolation and Coalescence (DCIC) technique is used to probe the phase behaviour and glass transition temperatures of ternary aerosol mixtures. The DCIC technique is used to perform temperature and relative humidity dependent viscosity measurements at viscosities near 5 × 106 Pa s. Measurements include organic-organic and organic-inorganic mixtures composed of sucrose-citric acid and sucrose-sodium nitrate. The data reported here add additional insight into the wide discrepancies in glass transition temperatures reported for pure sodium nitrate. The phase diagram model used in the work of Rothfuss and Petters (Phys. Chem. Chem. Phys., 2017, 19, 6532-6545) is expanded to include multiple solute components. Data and model predictions of the mixtures are in good agreement with the modified model. These measurements are compared with values from Holographic Optical Tweezer (HOT) measurements taken at room temperature. Overall, the viscosities determined from the DCIC and HOT techniques are in good agreement.

Temperature‐ and Humidity‐Dependent Phase States of Secondary Organic Aerosols

“…The graph can be interpreted as an amorphous phase state diagram. Conditions colder than the shaded area correspond to more viscous states, rapidly approaching glassy states ~20 to 30 °C below the observed transition (Figure and Marsh et al, ; Rothfuss & Petters, ). Conditions warmer than the shaded area correspond to less viscous states.…”

“…The uncertainty in this temperature is <2 °C based on the 95% confidence interval of the fit (Table S1). Uncertainty in estimated viscosity due to the assumed surface tension is negligible (Marsh et al, ). Estimated values for T g are 12–27 °C below the T associated with the 10 6 Pa·s transition.…”

“…Estimated values for T g are 12–27 °C below the T associated with the 10 6 Pa·s transition. The uncertainty of the extrapolated T g is ±10 °C based on validation with sucrose, citric acid, and binary mixtures of sucrose/citric acid and sucrose/sodium nitrate (Marsh et al, ; Rothfuss & Petters, ). Viscosity of dry SOAs covers a relatively narrow range and is similar to that of citric acid, coal tar pitch, and sorbitol.…”

“…Viscosity was calculated from monomer diameter (100 nm), coalescence time scale (5 s), and surface tension (0.03 N/m) using the algorithm of Rothfuss and Petters (). Calculations are described elsewhere (Marsh et al, ; Rothfuss & Petters, ) and in the SI. Surface tension was assumed based on typical values for pure organic liquids (Korosi & Kovats, ) and α‐pinene‐derived SOA (Hritz et al, ).…”

“…SOA was generated by oxidizing monoterpenes inside a laminar flow tube reactor. Variable T and RH were used to induce a viscous transition of particle dimers into spheres using an aerosol coalescence and isolation technique (Marsh et al, ; Rothfuss & Petters, , ). Dry experiments probed the T ‐dependent viscosity transition at 10 6 Pa·s and T g was determined by extrapolating to the glass transition viscosity.…”