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Researchers Develop Highly Elastic Form of Organic Crystal

Researchers from National Institute of Technology, Meghalaya, India, and New York University, Abu Dhabi invented an organic crystal that is thermally twistable, photo bendable, elastically deformable, and self-healable.

Crystals are fragile and rigid in composition. Its molecules are arranged in a highly ordered microscopic structure held together by interatomic forces forming a crystal lattice that extends in all directions. The first dynamic and adaptive molecular crystals properties were discussed in the paper On the Theory of the Elasticity of Crystals by Sir C. V. Raman and K. S. Viswanathan in 1955. The study noted that crystal structures can be quite elastic. The bendable, non- degradable crystals are attractive materials in microrobotics, flexible electronics, and optical devices. Now a new class of crystals engineered by researchers from National Institute of Technology, Meghalaya, India, and New York University, Abu Dhabi can twists and untwists upon heating and cooling. The novel form twists reversibly without disintegration under high temperature, mechanical force, or UV light. Moreover, the cracks formed in the process can self- heal over thermal cycling. The study was published in the journal Angewandte Chemie on June 18, 2018.

The crystalline nature of these substances is due to intermolecular interactions between hydrogen and aromatic rings that form a lattice spreading in all directions. The crystals created by the researchers consisted of two different molecules, probenecid and Dipyridin-4-yldiazene. Probenecid is a drug prescribed to enhance uric acid excretion and Dipyridin-4-yldiazene, is a heteroaromatic compound that is known to alter form when irradiated by UV light. The single crystals formed from these two molecules consist of stacked 2D layers in criss-cross arrangement. Heating the new crystal, rearranged the molecules to different packing angles, leading to a slight phase change. However, twisted form of the sheet of crystal was reversed after cooling and the molecular arrangement straightened again. Moreover, the cracking in the process healed once the crystal was subjected to UV light. Such organic crystals could enhance next-generation solid-state semiconductors, flexible electronics, and other technologies.