RESUMEN
In order to systematically explore the general rule of the host-guest chemistry for pillararenes, this work investigates the weak interactions between pillar[4]arene and some typical guests (anions, cations, and dumbbell-shaped molecules) by using density functional theory (DFT) calculations at the ωB97XD/6-311G(d,p) level. The strong molecular recognition ability of pillar[4]arene has been discussed based on the geometry structure, electronic structure, and thermodynamic properties of the host-guest complexes. The results show that the equivalent lower and upper rims of the pillar[4]arene can be combined with both anion and cation, and its cavity can accommodate the alkyl part of the dumbbell-shaped molecule. The main host-guest interactions between pillar[4]arene and guests are hydrogen bond, cation-π, anion-π, and hydrophobic interaction by visualization of weak interactions using the Multiwfn program. Pillar[4]arene will form a more stable host-guest complex with the guest, which possesses conjugate structure and weak steric repulsion. This work intends to provide a theoretical basis for enriching the host-guest chemistry, understanding the supramolecular morphology, and expanding the applications of the pillararenes.
RESUMEN
A fractal nanostructure having a high surface area is potentially useful in sensors, catalysts, functional coatings, and biomedical and electronic applications. Preparation of fractal nanostructures on solid substrates has been reported using various inorganic or organic compounds. However, achieving such a process using polymers in solution has been extremely challenging. Here, we report a simple one-shot preparation of polymer fractal nanostructures in solution via an unprecedented assembly mechanism controlled by polymerization and self-assembly kinetics. This was possible only because one monomer was significantly more reactive than the other, thereby easily forming a diblock copolymer microstructure. Then, the second insoluble block containing poly(p-phenylenevinylene) (PPV) without any side chains spontaneously underwent self-assembly during polymerization by an in situ nanoparticlization of conjugated polymers (INCP) method. The formation of fractal structures in solution was confirmed by various imaging techniques such as atomic force microscopy, transmission electron microscopy (TEM), and cryogenic TEM. The diffusion-limited aggregation theory was adopted to explain the branching patterns of the fractal nanostructures according to the changes in polymerization conditions such as the monomer concentration and the presence of additives. Finally, after detailed kinetic analyses, we proposed a plausible mechanism for the formation of unique fractal nanostructures, where the gradual formation and continuous growth of micelles in a chain-growth-like manner were accounted for.