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[摘要]：Self-assembling rigid-flexible block mols. consisting of a laterally extended arom. segment and different lengths of hydrophilic coils were synthesized and characterized. The block mol. based on a long poly(ethylene oxide) coil (1), in the melt state, shows an unidentified coil (2) self-organizes into an oblique columnar structure. Further decrease in the poly(ethylene oxide) coil length as in the case of 3, on heating, induces a rectangular columnar structure in addn. to an oblique columnar mesophase. In di-Et ether, 1 and 2 self-assemble into uniform nanofibers with bilayer packing. Remarkably, these elementary fibers further aggregate in a lateral way to form well-defined flat ribbons (1) and twisted ribbons (2) with solvent exchange of di-Et ether into methanol. Also, the ribbons formed in methanol dissocd. into elementary fibers in response to the addn. of arom. guest mols. This transformation between ribbons and single fibers in response to the addn. of guest mols. is attributed to the intercalation of arom. substrates within the rigid segments and subsequent loosening of the arom. stacking interactions. The introduction of a laterally extended arom. segment into an amphiphilic mol. architecture can lead to the hierarchical formation from elementary fibers of nanoribbons with a tunable twist through controlled lateral interactions between arom. segments. |
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