| 研究実績の概要 |
In the last fiscal year, we made an effort to compare the impact of terminal elongation and secondary nucleation-elongation in seeded supramolecular polymerization, which is crucial in studying the mechanism of mesoscale chainmail formation. Previously, to probe the mechanism of catenation of nanotoroids of diphenyl naphthalene barbiturates, we performed seeding experiments just below the nucleation temperature wherein spontaneous nucleation was delayed. Although toroidal seeds of the molecule remained stable in this supersaturated condition, helicoidal fiber seeds dissociated due to the presence of termini. To address this problem, we synthesized a new barbiturate containing quinoline in place of naphthalene. The new molecule tends to self-assemble more weakly than the previously studied barbiturates due to the presence of the electron-deficient quinoline unit, and thereby its spontaneous nucleation was suppressed enough even under ambient conditions where both closed and open-ended seeds remained stable. Seeding experiments under this condition using the two types of seeds allowed us to demonstrate the distinct kinetics of terminal elongation and secondary nucleation-elongation. We observed that open-ended helicoidal seeds induced terminal elongation leading to the formation of elongated helicoidal fibers. On the other hand, the closed-ended toroidal seeds induced secondary nucleation on their surface covered with alkyl chains, affording random coil structures. These results have been published in a paper recently.
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