Vitrification of octonary perylene mixtures with ultralow fragility

Abstract

Strong glass formers with a low fragility are highly sought-after because of the technological importance of vitrification. In the case of organic molecules and polymers, the lowest fragility values have been reported for single-component materials. Here, we establish that mixing of organic molecules can result in a marked reduction in fragility. Individual bay-substituted perylene derivatives display a high fragility of more than 70. Instead, slowly cooled perylene mixtures with more than three components undergo a liquid-liquid transition and turn into a strong glass former. Octonary perylene mixtures display a fragility of 13 ± 2, which not only is a record low value for organic molecules but also lies below values reported for the strongest known inorganic glass formers. Our work opens an avenue for the design of ultrastrong organic glass formers, which can be anticipated to find use in pharmaceutical science and organic electronics.

Room Temperature Dye Glasses: A Guideline Toward the Fabrication of Amorphous Dye Films with Monomeric Absorption and Emission

“…As a consequence, both rates are highly affected by the temperature dependence of the viscosity above T g and therefore the cooling rate. How the viscosity of a liquid increases upon cooling at the T g is described by its kinetic fragility ( m ). , This measure is also used to classify glass-formers into fragile and strong glass-formers …”

“…Another factor is the number of different components. This naturally affects the entropy of the system upon mixing (Δ S mix ) and has also been shown to affect the kinetic fragility of multicomponent mixtures . In the system used in this work, the components are designed to have highly similar molecular structures.…”

“…Furthermore, in all cases the slope is constant, indicating that no liquid–liquid transition occurs. We have previously experienced the occurrence of liquid–liquid transitions in dye glasses, leading to low fragility but also aggregation and an associated change in the emission envelope . In the present study, we see no tendency of a liquid–liquid transition in the FSC data nor an aggregation associated change of the emission.…”

Synergistic effects of side-functionalization and aza-substitution on the charge transport and optical properties of perylene-based organic materials: a DFT study

“…with necessary structural modifications have been extensively studied so far. 6–13 By chemically modifying these π-conjugated systems with various functional groups, it is possible to tune their electronic, optical, and charge transport properties. Though the hole mobilities of certain OSCs ( e.g.…”

“…with necessary structural modifications have been extensively studied so far. [6][7][8][9][10][11][12][13] By chemically modifying these p-conjugated systems with various functional groups, it is possible to tune their electronic, optical, and charge transport properties. Though the hole mobilities of certain OSCs (e.g., pentacene, rubrene) have been addressed up to the mark (B40 cm 2 V À1 s À1 in rubrene 14 ), the aspects such as air-stability and electron transporting ability of OSCs are still under debate.…”