Vapor-deposited alcohol glasses reveal a wide range of kinetic stability

Abstract

In situ AC nanocalorimetry was used to characterize vapor-deposited glasses of six mono- and di-alcohol molecules. Benzyl alcohol glasses with high kinetic stability and decreased heat capacity were prepared. When annealed above the glass transition temperature T_g, transformation of these glasses into the supercooled liquid took 10^3.4 times longer than the supercooled liquid relaxation time (τ_α). This kinetic stability is similar to other highly stable organic glasses prepared by vapor deposition and is the first clear demonstration of an alcohol forming a stable glass. Vapor deposited glasses of five other alcohols exhibited moderate or low kinetic stability with isothermal transformation times ranging from 10^0.7 to 10² τ_α. This wide range of kinetic stabilities is useful for investigating the factors that control stable glass formation. Using our current results and literature data, we compare the kinetic stability of vapor deposited glasses prepared from 14 molecules and find a correlation with the value of τ_α at 1.25 T_g. We also observe that some vapor-deposited glasses exhibit decreased heat capacity without increased kinetic stability.