Solid-state polymorphic transition and solvent-free self-assembly in the growth of organic crystalline microfibers

The study of the crystalline xerogel formed by a newly synthesized L-valine and pyridine containing low-molecular-weight gelator reveals a polymorphic transition above 225 degrees C that is followed by the formation of microfibers. The habitus of the fibers grown remains stable upon cooling. Microscopic observations lead to the suggestion that after the polymorphic transition, the fibers are formed by a sublimation process. Results obtained reveal the intrinsic tendency of this compound to self-assemble anisotropically in fibers that permit the preparation of organic crystalline micro- and nanofibers in solvent-free conditions.