Role of hydrogen bonding in the formation of glasses by small molecules: a triazine case study

Abstract

Diaminotriazine derivatives with 3,5-dimethylphenyl groups have been shown to be capable of readily forming extremely stable glassy phases under ambient conditions, and self-assembly through hydrogen bonding has been thought to be a key element in this process. Herein, we probed the role played by hydrogen bonding in glass formation in this family of compounds by studying the crystal structures of both molecular glasses and closely similar compounds that crystallize under ambient conditions. We also compared a molecular glass in the crystalline and amorphous states by FTIR spectroscopy to monitor changes at the molecular level as the material underwent glass transition. We have shown that hydrogen bonding favors glass formation through the formation of aggregates that pack poorly, and breaking of hydrogen bonds plays a role in the physical changes associated with glass transition.