Co-crystallization in Blends of Complementary Sequence-Defined Mesogenic Dimers

Molecules that favor a bent molecular conformation can achieve an array of unique liquid crystalline and crystalline structures such as the 'B-phases'. This work examines the self-assembly of two achiral, asymmetric mesogenic heterodimers of alternating monomer sequence that differ in the placement of a methyl group, and which are hypothesized to favor a bent intermesogen geometry. Both heterodimers form nanocylinders ~150 nm in diameter but possess different chiral manifestations in each dimer: they adopt chiral domains that exhibit optical rotation or form a nanocylinder arrangement featuring planar chirality. Near equimolar heterodimer blends co-crystallize to form twisted ribbons rather than the nanocylinders observed in the pure dimers. Optical characterization reveals radial optical banding as well as coexisting domains of opposite chiral sense within individual spherulites. We also demonstrate that we can achieve an extremely high degree of long-range order and alignment in nanocylinders through seeded nucleation followed by slow high-temperature isothermal crystallization.