Organic Glasses of High Glass Transition Temperatures Due To Substitution with Nitrile Groups

The glass transition temperature (T_g) of a molecular glass depends on its molar mass. However, the nature of intermolecular interactions also plays a major role in both the glass transition temperature and its glass-forming ability. In this context, we report on novel molecular glasses containing nitrile groups and investigate the influence of this highly polar group on T_g and the glass-forming ability. As reference compounds, we studied the thermal properties of synthesized molecular glasses with C-C-bonded phenyl rings. The molar mass of the studied compounds ranges from 341 to 568 g/mol. Despite their relatively low molar mass, glass transition temperatures from 347 K (74 °C) to 471 K (198 °C) were observed. Most of the compounds possess high T_g/T_mratios between 0.7 and 0.8. By introducing highly interacting nitrile groups, the dependence of the molar mass on T_g could be increased by a factor of 2-3.