Design of a homologous series of molecular glassformers

Abstract

We design and synthesize a set of homologous organic molecules by taking advantage of facile and tailorable Suzuki cross coupling reactions to produce triarylbenzene derivatives. By adjusting the number and the arrangement of conjugated rings, the identity of heteroatoms, lengths of fluorinated alkyl chains, and other interaction parameters, we create a library of glassformers with a wide range of properties. Measurements of the glass transition temperature (Tg) show a power-law relationship between Tg and molecular weight (MW), with of the molecules, with an exponent of 0.3 ± 0.1, for Tg values spanning a range of 300–450 K. The trends in indices of refraction and expansion coefficients indicate a general increase in the glass density with MW, consistent with the trends observed in Tg variations. A notable exception to these trends was observed with the addition of alkyl and fluorinated alkyl groups, which significantly reduced Tg and increased the dynamical fragility (which is otherwise insensitive to MW). This is an indication of reduced density and increased packing frustrations in these systems, which is also corroborated by the observations of the decreasing index of refraction with increasing length of these groups. These data were used to launch a new database for glassforming materials, glass.apps.sas.upenn.edu.

Dissymmetric Triaryltriazines: Small Mass Columnar Glasses

“…3.5 Å. The hexagonal nature of mesophase of the two derivatives 14 and 15 with two extended aryl arms is evident from the presence of the (11) secondary lattice peak corresponding to a q ratio of p 3 to the main (10) lattice peak. In 15 at room temperature, the (21) peak (q ratio of p 7 to main peak) is also discernible.…”

“…[10] Although the glass transition temperature T g generally correlates strongly with molecular weight, the addition of flexible side chains leads to a decrease of T g . [11] Such side chains are a key ingredient to columnar liquid crystals, but several low-symmetry arenes have been reported to form columnar mesophases in the absence of elongated side chains, examples being polychlorinated indene derivatives [12] and 1,2,3,4-tetrafluoro-6,7,10,11-tetramethoxy-triphenylene. [13] Uniform alignment of columnar LC glasses has been achieved by controlled physical vapor deposition (PVD), and the entropy content of the glass state can be modulated by the deposition conditions.…”

Role of Molecular Layering in the Enhanced Mechanical Properties of Stable Glasses

“…45,52 The glass-transition temperatures (T g ) of these molecule, as determined by differential scanning calorimetry (DSC), are T g,−A = 361 ± 2 K and T g,−Phen = 362 ± 5 K, respectively. 45,52 As reported in our previous work, 25 diarylbenzene bond in α,α−A has a higher barrier of dihedral rotation compared to the Phen−diarylbenzene bond in α, α− Phen. The equilibrium angle of this dihedral bond in α,α−A is also larger than the corresponding bond in α,α−Phen.…”

“…Materials . Figure A shows the structures of 9-(3,5-di­(naphthalen-1-yl)­phenyl)­anthracene (α,α–A) and 9-(3,5-di­(naphthalen-1-yl)­phenyl)­phenanthrene (α,α–Phen) molecules, which were synthesized as described in our previous work. , The glass-transition temperatures ( T g ) of these molecule, as determined by differential scanning calorimetry (DSC), are T g,–A = 361 ± 2 K and T g,–Phen = 362 ± 5 K, respectively. , As reported in our previous work, the A–diarylbenzene bond in α,α–A has a higher barrier of dihedral rotation compared to the Phen–diarylbenzene bond in α, α–Phen. The equilibrium angle of this dihedral bond in α,α–A is also larger than the corresponding bond in α,α–Phen.…”

An algorithm to classify homologous series within compound datasets

“…1 ). In drug design, homologation is used as a molecular modification strategy to construct series for lead optimisation [ 2 ], while homologous series are prominent in pesticide synthesis [ 3 ], food [ 4 ], and material science [ 5 ], as well as formulation chemistry [ 6 ] for applications in myriad products such as cosmetics, surfactants, and pharmaceuticals. In nature, homologous series occur as natural products of multiple organisms including bacteria [ 7 ], fungi [ 8 ], marine sponges [ 9 , 10 ], birds [ 11 ], bees [ 12 ], and avocados [ 13 ].…”