Thermal expansion involves a response of a material to an external stimulus that typically involves an increase in a crystallographic axis (positive thermal expansion (PTE)), although shrinking with applied heat (negative thermal expansion (NTE)) is known in rarer cases. Here, we demonstrate a means to achieve dynamic molecular motion and thermal expansions in organic solids via co-crystallizations. One co-crystal component is known to exhibit dynamic behaviour in the solid state while the second, when varied systematically, affords co-crystals with linear thermal expansion coefficients that range from colossal to nearly zero. Two co-crystals exhibit rare NTE. We expect the approach to guide the design of molecular solids that enable predesigned motion related to thermal expansion processes.
Hutchins, K. M., Groeneman, R. H., Reinheimer, E. W., Swenson, D. C., & MacGillivray, L. R. (2015). Achieving dynamic behaviour and thermal expansion in the organic solid state via co-crystallization. Chemical Science, 6(8), 4717–4722. https://doi.org/10.1039/c5sc00988j