title: Formation of rigid organic nanotubes with controlled internal cavity based on frustrated aggregate internal rearrangement mechanism.
abstract: We introduce frustrated aggregate internal rearrangement (FAIR) mechanism for anisotropic higher-order structure formations, in which the anisotropy arose due to the structural frustration. We demonstrate the FAIR mechanism by investigating the recently observed rigid organic nanotube formations through the self-assembly of building blocks, which include rigid segments and make intermolecular H-bonds, whereas the principle of the FAIR mechanism is general and is not limited to H-bonding building blocks or nanotube formations. Initially, molecules aggregate into sheetlike structures driven by nonspecific and nondirectional intermolecular interactions such as π-π stacking or amphiphilicity. Weak intermolecular H-bonds provide additional stability to the structure. Within the aggregate, however, not all molecules have the right orientation for specific and directional H-bonds whereas collective internal rearrangement of rigid building blocks requires a large amount of energy to overcome kinetically trapped barriers. Consequently, instead of the fully H-bonded global equilibrium structure, self-assembled layers become trapped with partial and disordered H-bonding schemes at various fractions leading to an anisotropic layer that undergoes spontaneous transformation into curved structures. The FAIR mechanism can readily be extended to anisotropic higher-order structures other than nanotubes and to the assembly of diverse building blocks including hybrids such as polymer nanocomposites. Also the reversible transformation from metastable nanotubes into layered sheets is potentially useful for controlling internal cavity size of nanotubes.
authors.affiliation: Department of Chemistry and Institute of Nano-Bio Molecular Assemblies, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul 120-749, Korea.
authors.forename: Minwoo
authors.initials: M
authors.lastname: Han
authors.forename: Jungin
authors.initials: J
authors.lastname: Hyun
authors.forename: Eunji
authors.initials: E
authors.lastname: Sim
mesh_terms: D006860:Hydrogen Bonding; D043942:Nanotubes / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011409:Propylene Glycols / Q000737:chemistry
chemical_list: D011108:Polymers; D011409:Propylene Glycols; C012504:polypropylene glycol