Synthesis and Characterization of Sequence Defined Monodisperse Liquid Crystalline Oligomers

The actuation and soft elastic behavior of liquid crystal (LC) polymers have led to their use in applications ranging from soft robotics to elastocaloric devices. However, the behavior of a main-chain LC polymer differs markedly from that of its constituent monomer and is influenced by factors including molecular weight, sequence, and molecular weight dispersity. LC oligomers and polymers of controlled length and sequence are challenging to achieve through typical step-growth LC synthetic strategies. As such, we demonstrate a new LC synthetic approach based on iterative exponential growth (IEG) to prepare a series of monodisperse triazole-linked LC oligomers of precise lengths. We map the effects of increasing molecular weight on the thermal transitions of these discrete LC materials. These results are contrasted with the behavior of comparable species prepared via conventional step-growth polymerization. Furthermore, by preparing LC monomers decorated with different functional groups, sequence-defined co-oligomers and co-polymers can be prepared, illustrating the effects of sequence and functionality on LC phase behavior. These studies highlight important factors affecting LC phase transitions, establishing design rules for tailored and precise LC behavior.