A type of structural transformation typically linked to hardening steel and enabling shape-memory alloys—known as a martensitic transformation—may also occur in liquid crystals, according to new research from Rice University. This discovery, published in the Proceedings of the National Academy of Sciences, shows that an organic semiconductor can transition from a liquid crystal to a solid crystal through a rapid, highly coordinated process similar to the martensitic transformation, which usually involves changes between two solid crystalline structures. The researchers studied a compound called HAT6, an organic semiconductor composed of disk-shaped molecules that form columns in its liquid-crystalline state. By aligning these columns inside microscopic channels and rapidly cooling the material, they induced a transition to a solid crystal. When cooled quickly, the resulting crystal retained about 70% of the molecular alignment present in the liquid crystal. However, when cooled more slowly, the molecules rearranged, and the alignment was gradually lost. The transformation occurred only within a very specific cooling range. The material had to cool quickly enough to avoid forming a disordered glass but not so fast that it prevented the formation of a crystalline structure. This process was also exceptionally fast, with the crystal forming at a rate of about 100 micrometers per second—over 10 million times faster than conventional crystal growth models predict under similar conditions. To observe the changes in molecular orientation during cooling and reheating, the researchers used polarized optical microscopy. X-ray measurements at the Stanford Synchrotron Radiation Lightsource confirmed the structure of the resulting crystals. Importantly, the transformation was largely reversible, with the original molecular alignment largely restored when the material was reheated back into its liquid-crystalline phase. The study suggests that the physics behind these transformations may apply to more states of matter than previously thought. While the researchers tested other liquid crystals, they did not observe the same level of molecular order preservation, indicating that only specific molecular structures may support this kind of cooperative transformation. This finding could help solve a long-standing issue in organic electronics, where the performance of carbon-based semiconductors is heavily influenced by the arrangement of their molecules. The study’s authors propose that the alignment seen in liquid crystals could serve as a template for creating highly ordered crystalline materials, potentially advancing the field of organic electronics.