Creation of macroscopic chiral structures through twisting crystal growth and exploration of their functions

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Twisted growth of various inorganic and organic crystals was investigated by using organic matrix. Oriented assembly of micrometric twisted crystals on a glass substrate was achieved through dipping of an aqueous solution containing of K_2Cr_2O_7 and poly(acrylic acid). The oriented microstructures of K_2Cr_2O_7 exhibited a unique optical property originating from the periodic twisted crystal growth. The crystal morphology of an organic molecule, pyrene, formed in an organic solvent changed from polyhedral shapes into characteristic curving forms, such as sigmoidal and helical architectures, with increasing the concentration of a polymer, polyvinyl pyrrolidone. The curving forms are inferred to be constructed through a twisted assembly of asymmetric units under diffusion-limited conditions. The controlled growth of inorganic and organic crystals using the polymer matrix would provide a novel type of functional materials having macroscopic chirality.