Prediction of the Synergistic Glass Transition Temperature of Coamorphous Molecular Glasses Using Activity Coefficient Models.

The glass transition temperature () of a binary miscible mixture of molecular glasses, termed a coamorphous glass, is often synergistically increased over that expected for an athermal mixture due to the strong interactions between the two components. This synergistic interaction is particularly important for the formulation of coamorphous pharmaceuticals since the molecular interactions and resulting strongly impact stability against crystallization, dissolution kinetics, and bioavailability. Current models that describe the composition dependence of for binary systems, including the Gordon-Taylor, Fox, Kwei, and Braun-Kovacs equations, fail to describe the behavior of coamorphous pharmaceuticals using parameters consistent with experimental Δ and Δα.

The glass transition and enthalpy recovery of a single polystyrene ultrathin film using Flash DSC.

The kinetics of the glass transition are measured for a single polystyrene ultrathin film of 20 nm thickness using Flash differential scanning calorimetry (DSC). T is measured over a range of cooling rates from 0.1 to 1000 K/s and is depressed compared to the bulk.

Crystallization and vitrification of a cyanurate trimer in nanopores.

The effects of nanopore confinement on the crystallization and vitrification of a low molecular weight organic material, tris(4-cumylphenol)-1,3,5-triazine, are investigated using differential scanning calorimetry. The material shows cold crystallization and subsequent melting in the bulk state. Under the nanoconfinement of controlled pore glasses (CPG), cold crystallization and melting shift to lower temperatures.

Kinetic study of trimerization of monocyanate ester in nanopores.

A kinetic study of the trimerization of monocyanate ester both in the bulk and in the nanoconfinement of controlled pore glass is performed using differential scanning calorimetry. Both isothermal and dynamic experiments are analyzed. Although the activation energy for the reaction is the same within experimental error for the bulk and nanoconfined samples (approximately 21-23 kcal/mol), the reaction is accelerated under nanoconfinement by approximately 50 times in 13 nm pores compared with bulk.

Trimerization of monocyanate ester in nanopores.

The effects of nanoconfinement on the reaction kinetics and properties of a monocyanate ester and the resulting cyanurate trimer are studied using differential scanning calorimetry (DSC). On the basis of both dynamic heating scans and isothermal reaction studies, the reaction rate is found to increase with decreasing nanopore size without a change in reaction mechanism. Both the monocyanate ester reactant and cyanurate product show reduced glass transition temperatures (T(g)s) as compared to the bulk; the T(g) depression increases with conversion and is more pronounced for the fully reacted product, suggesting that molecular stiffness influences the magnitude of nanoconfinement effects.