2022-03-312022-03-312020Ding, X., Unruh, D. K., Groeneman, R. H., & Hutchins, K. M. (2020). Controlling thermal expansion within mixed cocrystals by tuning molecular motion capability. Chemical Science, 11(29), 7701-7707. https://doi.org/10.1039/D0SC02795Bhttps://doi.org/10.1039/D0SC02795Bhttps://hdl.handle.net/2346/88899This journal is © The Royal Society of Chemistry 2020. This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. All publication charges for this article have been paid for by the Royal Society of Chemistry.Controlling thermal expansion (TE) behaviors of organic materials is challenging because several mechanisms can govern TE, such as noncovalent interaction strength and structural motions. Here, we report the first demonstration of tuning TE within organic solids by using a mixed cocrystal approach. The mixed cocrystals contain three unique molecules, two of which are present in variable ratios. These two molecules either lack or exhibit the ability to undergo molecular motion in the solid state. Incorporation of higher ratios of motion-capable molecules results in larger, positive TE along the motion direction. Addition of a motion-incapable molecule affords solids that undergo less TE. Fine-tuned TE behavior was attained by systematically controlling the ratio of motion-capable and -incapable molecules in each solid.engThermal ExpansionMolecular MotionArticle