Supercooling of functional alkyl-π molecular liquids

Abstract

Metastable states of soft matters are extensively used in designing stimuli-responsive materials. However, the non-steady properties may obstruct consistent performance. Here we report an approach to eradicate the indistinguishable metastable supercooled state of functional molecular liquids (FMLs), which remains as a liquid for weeks or months before crystallizing, <i>via</i> rational molecular design. The phases (solid, kinetically stable liquid, and supercooled liquid) of a model FML, branched alkyl chain-substituted 9,10-diphenylanthracene (<b>DPA</b>), are found to be governed by subtle alterations of the molecular structure (alkyl-<b>DPA</b> ratio and bulkiness of the <b>DPA</b> unit). We thus outline molecular design principles to avoid supercooled FML formation. Moreover, we demonstrate a practical technique to rapidly discriminate supercooled FMLs (within 5 h) by accelerating their crystallization in differential scanning calorimetry heating <i>via</i> pre-annealing or relatively slow scanning.