Abstract. Glass transitions from liquid to semi-solid and solid phase states
have important implications for reactivity, growth, and cloud-forming (cloud
condensation nuclei and ice nucleation) capabilities of secondary organic
aerosols (SOAs). The small size and relatively low mass concentration of SOAs
in the atmosphere make it difficult to measure atmospheric SOA glass
transitions using conventional methods. To circumvent these difficulties, we
have adapted a new technique for measuring glass-forming properties of
atmospherically relevant organic aerosols. Aerosol particles to be studied
are deposited in the form of a thin film onto an interdigitated electrode
(IDE) using electrostatic precipitation. Dielectric spectroscopy provides
dipole relaxation rates for organic aerosols as a function of temperature
(373 to 233 K) that are used to calculate the glass transition temperatures
for several cooling or heating rates. IDE-enabled broadband dielectric
spectroscopy (BDS) was successfully used to measure the kinetically
controlled glass transition temperatures of aerosols consisting of glycerol
and four other compounds with selected cooling and heating rates. The glass
transition results agree well with available literature data for these five
compounds. The results indicate that the IDE-BDS method can provide accurate
glass transition data for organic aerosols under atmospheric conditions. The
BDS data obtained with the IDE-BDS technique can be used to characterize
glass transitions for both simulated and ambient organic aerosols and to
model their climate effects.
Glassy dynamics of poly(2-vinyl-pyridine) brushes with varying grafting density