EFFECT OF HYDROGEN BOND FORMATION ON PHYSICAL AGING OF ETHYLENE-VINYL ALCOHOL COPOLYMERS WITH ANNEALING BELOW <i>T</i>_g

The Effect of Annealing on the Stability of Amorphous Solids: Chemical Stability of Freeze-Dried Moxalactam

“…In the initial phase of glass formation, configurations of the ''substates'' are considered to be ''frozen-in'' during processing. [27][28][29] After glass formation, various regions relax at different rates. That is, there is a distribution of relaxation times.…”

“…40 These reactions occur since there is sufficient molecular mobility and free volume in the amorphous state to facilitate the acquisition of molecular configurations favorable for a chemical or physical reaction (or both) to occur. [27][28][29][30][31]33,[35][36][37][38][39] Since both chemical degradation and structural relaxation in the solid state require molecular mobility of some type, it is expected that chemical stability and structural relaxation are correlated. 6,27,33,37 Moreover if the molecular mobility required for a certain degradation reaction to occur requires the same type of mobility as structural relaxation, then relaxation time and stability should be proportional.…”

The Challenge of Drying Method Selection for Protein Pharmaceuticals: Product Quality Implications

“…Although the high viscosity in a glass (>10 12 Pa·s) greatly slows the α‐relaxations,137,138 many reactions do proceed at a measurable rate below T g ,134,135,137,139–147 whether the reaction is unimolecular or bimolecular,147 for example, chemical reactions or aggregation 141. The fact that these reactions occur means there is sufficient molecular mobility and free volume in the amorphous state to allow the acquisition of molecular configurations favorable for a chemical or physical reaction (or both) to occur 134,135,141–146,148–150. Since both degradation and structural relaxation in the solid state require motion of some type, it is expected that storage stability and structural relaxation are correlated 113,143,145,148.…”

To the editor

“…A glass is assumed to be a collection of “substates” or a heterogeneous set of microscopic regions (micro‐domains) of various sizes and configurational entropies ( S C ). In the initial phase of glass formation, configurations of the “substates” are considered to be “frozen‐in” during processing 27–29. After glass formation, various regions relax at different rates.…”

“…Although the high viscosity of a glass (>10 12 Pa · s) greatly slows molecular mobility,11, 13 many reactions do proceed at a measurable rate below T g ,7, 8, 11, 29, 31, 33, 35–40 regardless of whether the reaction is unimolecular or bimolecular 40. These reactions occur since there is sufficient molecular mobility and free volume in the amorphous state to facilitate the acquisition of molecular configurations favorable for a chemical or physical reaction (or both) to occur 27–31, 33, 35–39. Since both chemical degradation and structural relaxation in the solid state require molecular mobility of some type, it is expected that chemical stability and structural relaxation are correlated 6, 27, 33, 37.…”