矢貝 史樹

Self-organization of a series of co-aggregates consisting of merocyanine dye 1 and dimeric melamines BM were examined both in solution and in solid state using dynamic light scattering (DLS), X-ray diffraction and microscopic techniques. DLS study indicates that these coaggregates exist as extended polymeric species or discrete 1+1 closed species in solution state. The stable 1+1 closed species formed from 1+BM and 1+BM were found to organize into columnar assembly, resulting in the formation of nanofibers with high aspect ratio. On the other hand, extended supramolecular polymer species were found for 1+BM to 1+BM , but their self-organization behaviors were quite different as indicated by dramatically different gelation behavior of the concentrated solutions and X-ray diffraction patterns of the solid samples. n 5 7 8 12

Hydrogen-bond-directed supramolecular polymerization of bay-substituted perylene bisimide 1 and dimeric melamine 2 featuring flexible tether has been investigated using UV-vis spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Methylcyclohexane solution of the 1:1 molar mixture (c = 100 μM) gave aggregates with average hydrodynamic diameters of ca. 80-nm as estimated from DLS. UV-vis measurements revealed that the perylene chromophores exist as strongly π-π stacked state upon supramolecular polymerization. SEM observation of the dried film obtained from the MCH solution visualized the fibrous architectures with width of 1 μm. Furthermore, AFM observation revealed that the fibers are hierarchically constructed from both right-handed and left-handed helical nanofibers with diameters of ca. 10 nm in spite of the absence of any chiral centers in both the components.

Aggregation between azobenzene-appended melamine 1 and perylene bisimide 2 is investigated using UV/Vis spectroscopy and dynamic light scattering (DLS). UV/Vis measurements revealed that, at low concentrations (10 μM), 1 and 2 exist as monomeric state in dichloromethane whereas they exist as co-aggregated state in MCH. The DLS analysis of MCH solution showed the presence of aggregates with an average hydrodynamic diameter of ca. 60 nm at 100 μM. The trans→ cis isomerization of the azobenzene moieties of 2 were observed upon the irradiation of UV-light for the mixture in dichloromethane. In contrast, photoisomerization was completely suppressed in MCH. Though the mixture of 1 containing trans-azobenzene moieties and 2 was highly soluble in MCH, the mixture of 1 with cis-azobenzene moieties and 2 showed low solubility in MCH.