Influence of isomeric ratio on stable glass forming ability and secondary relaxations in vapor-deposited mixtures of <i>cis/trans-</i>decahydroisoquinoline

While many organic molecules can form highly stable glasses using physical vapor deposition (PVD), the stable glass forming ability of co-deposited mixtures is a relatively unexplored area. Here, we use in situ AC nanocalorimetry and interdigitated electrode broadband dielectric spectroscopy to explore the effect of varying the ratio of cis/trans isomers in vapor-deposited glasses of decahydroisoquinoline (DHIQ). DHIQ is a structural analogue of decahydronaphthalene (decalin) with a carbon to nitrogen substitution endowing it with a much larger dipole moment than decalin. Glasses of varying kinetic stability were prepared based on preparation temperature and isomeric ratio. Stable glasses displayed lower amplitude secondary relaxations relative to liquid-cooled glasses. This work broadens the scope of stable glass forming mixtures that can be prepared by PVD, expanding upon our previous work on cis/trans-decalin mixtures.