Hisanari Onouchi

Stiffness- and Conformation-Dependent Polymer Wrapping onto Single-Walled Carbon Nanotubes

This work reports the effect of stiffness and conformation of chain-like polymers on wrapping behaviors around single-walled carbon nanotubes (SWNT). As a model of chain-like polymers, three kinds of poly(dialkylsilane) (PSi)s with random-coiled, flexible, and semiflexible main chains were employed. Complexes of PSi and SWNT were prepared using mechanochemical high-speed vibration milling (HSVM). Stiffness-dependent polymer wrapping behaviors were investigated using combinational analyses with a differential scanning calorimeter, transmission electron microscopy, and atomic force microscopy. Furthermore, the conformational behaviors of the PSis wrapped onto SWNTs were characterized spectroscopically with ordinary UV spectroscopy. Random-coiled and flexible PSis were successfully wrapped onto small bundles of SWNTs, in which their conformations were changed to fit the surface curvatures of the SWNTs. However, semiflexible PSi could not form a complex with SWNTs, and its conformation remained unchanged even after the same HSVM process. Knowledge gained from this study may lead to a new approach to molecular design of chain-like polymers for efficient wrapping materials for SWNTs.

Latticelike Smectic Liquid Crystal Phase in a Rigid-Rod Helical Polyisocyanide with Mesogenic Pendants

We report a unique macromolecule consisting of a rodlike helical polyisocyanide backbone with a narrow molecular weight distribution and rigid mesogenic chiral pendants linked via a flexible spacer that exhibits lyotropic nematic and latticelike new smectic (lat-Sm) liquid crystal phases at different concentrations. The unprecedented lat-Sm phase is associated with the smectic ordering of both the stiff polymer backbone and the rigid-rod side groups. A detailed investigation of the films using X-ray scattering and atomic force microscopy revealed a novel tilted smectic layer structure of the polymer backbone aligned perpendicular to the smectic layer of the mesogenic pendants, which arrange in an antiparallel overlapping interdigitated manner.

Binding of Organic Anions by Synthetic Supramolecular Metallopores with Internal Mg2+–Aspartate Complexes

We report that cation‐selective transmembrane pores formed by synthetic p‐octiphenyl β barrels with internal aspartate residues can be transformed into anion‐permeable metallopores with internal Mg2+–aspartate complexes. These metallopores are shown to be useful for fluorimetric sensing of a broad variety of organic anions of biological relevance such as phytate, heparin, thiamine phosphates, and adenosine triphosphate. The negligible flippase activity measurable for Mg2+‐free pores indicates that transmembrane p‐octiphenyl β barrels do not disturb the lipid bilayer suprastructure, in other words, they form barrel–stave rather than toroidal pores.