Sequence and molecular weight controlled phase behavior of liquid crystalline oligomers*

In polymeric liquid crystals (LCs), it is often difficult to deconvolute the effects of the mesogenic core from those of molecular weight (and its dispersity), non-mesogenic dilutions, and topology (such as linker length and branching). To better understand these relationships and target specific LC phase behavior, we employed an iterative exponential growth synthetic strategy to combine two mesogenic cores and prepare monodisperse triazole-linked LC oligomers of precise lengths and sequence. We analyzed the phase transitions of these oligomers using calorimetric techniques, contrasting them with those of comparable species prepared via conventional step-growth polymerization. The structures of these phases were elucidated through optical and X-ray studies, revealing phase behavior that is dependent on both molecular length and mesogenic sequence. We highlight the thermodynamic and kinetic factors determining phase transitions in these materials, thus developing design rules for tailored and precise LC behavior.