矢貝 史樹

Abstract Despite being a promising soft material embodied by molecular self-assembly, the formation mechanism of supramolecular gels remains challenging to fully understand. Here we provide molecular to nanoscopic insights into the formation mechanism of gel-forming fibers from a urea derivative. High-speed atomic force microscopy of the urea derivative revealed the presence of a lag phase prior to the formation of supramolecular fibers, suggesting a nucleation process. The fiber growth kinetics differ at both termini of the fiber, indicating a directional hydrogen-bonding motif by the urea units, which is supported by single-crystal X-ray crystallography of a reference compound. Moreover, we observed an intermittent growth pattern of the fibers with repeated elongation and pause phases. This unique behavior can be simulated by a theoretical block-stacking model. A statistical analysis of the concentration-dependent lag time on macroscopic observation of the gelation suggests the presence of a tetrameric or octameric nucleus of the urea molecules.

A quinazoline‐2,4(1H,3H)‐dione bearing a phenylene moiety and aliphatic tails was synthesized as an alternative self‐assembling building block to barbiturate molecules, aiming to achieve enhanced hydrolysis resistance. The compound self‐assembles in non‐polar solvents to form linear supramolecular polymers via the formation of hydrogen‐bonded cyclic hexamers (rosettes), a process confirmed by powder X‐ray diffraction (PXRD) analysis of the bulk material. Our results demonstrate that quinazoline‐2,4(1H,3H)‐dione serves as an effective hydrogen‐bonding building block, suggesting its potential to form stable supramolecular polymers from versatile π‐conjugated molecules.