Molecular weight fractionation by confinement of polymer in one-dimensional pillar[5]arene channels.

Confinement of polymers in nano-spaces can induce unique molecular dynamics and properties. Here we show molecular weight fractionation by the confinement of single polymer chains of poly(ethylene oxide) (PEO) in the one-dimensional (1D) channels of crystalline pillar[5]arene. Pillar[5]arene crystals are activated by heating under reduced pressure.

Host-Guest Complexation Using Pillar[5]arene Crystals: Crystal-Structure Dependent Uptake, Release, and Molecular Dynamics of an Alkane Guest.

Host-guest complexation has been mainly investigated in solution, and it is unclear how guest molecules access the assembled structures of host and dynamics of guest molecules in the crystal state. In this study, we studied the uptake, release, and molecular dynamics of n-hexane vapor in the crystal state of pillar[5]arenes bearing different substituents. Pillar[5]arene bearing 10 ethyl groups yielded a crystal structure of herringbone-type 1:1 complexes with n-hexane, whereas pillar[5]arene with 10 allyl groups formed 1:1 complexes featuring a one-dimensional (1D) channel structure.

Separation of Linear and Branched Alkanes Using Host-Guest Complexation of Cyclic and Branched Alkane Vapors by Crystal State Pillar[6]arene.

Activated crystals of pillar[6]arene produced by removing the solvent upon heating were able to take up branched and cyclic alkane vapors as a consequence of their gate-opening behavior. The uptake of branched and cyclic alkane vapors by the activated crystals of pillar[6]arene induced a crystal transformation to form one-dimensional channel structures. However, the activated crystals of pillar[6]arene hardly took up linear alkane vapors because the cavity size of pillar[6]arene is too large to form stable complexes with linear alkanes.

Alkane-length sorting using activated pillar[5]arene crystals.

We report a simple and easy-to-operate method for separating n-alkanes: when we immersed activated pillar[5]arene crystals into a mixture of n-alkanes with various chain lengths, the crystals preferentially took up n-alkanes with longer chain lengths.

The controlled synthesis of pillar[6]arene-based hexagonal cylindrical structures on an electrode surface via electrochemical oxidation.

Electrochemical oxidation of pillar[6]arene containing six hydroquinones resulted in the formation of hexagonal cylindrical structures on an electrode surface driven by charge transfer interaction. The electrochemical approach successfully controlled the size and shape of the structures.

Spherical Vesicles Formed by Co-Assembly of Cyclic Pentagonal Pillar[5]quinone with Cyclic Hexagonal Pillar[6]arene.

Mixing cyclic pentagonal pillar[5]quinone with cyclic hexagonal pillar[6]arene in a 12:20 molar feed ratio resulted in spontaneous production of vesicles, while assembly of pillar[6]arene and pillar[5]quinone alone produced hexagonal disks and wires, respectively. Incorporation of pentagonal pillar[5]quinone rings into hexagonal pillar[6]arene sheets gave curvature and contributed to the formation of vesicles. Conventional vesicles are generally synthesized by assembly of amphiphilic molecules containing hydrophobic and hydrophilic parts.

Host-Guest Complexation of Perethylated Pillar[5]arene with Alkanes in the Crystal State.

Activated perethylated pillar[5]arene crystals show an unexpected alkane-shape- and -length-selective gate-opening behavior. Activated crystals were obtained upon removing solvents from perethylated pillar[5]arene crystals by heating. The activated crystals could quantitatively take up n-alkanes with carbon chains containing more than five carbon atoms as a consequence of their gate-opening pressure.

Porous Carbon Fibers Containing Pores with Sizes Controlled at the Ångstrom Level by the Cavity Size of Pillar[6]arene.

We report a new synthesis method of fibrous carbon material with pores sizes that are precisely controlled at the Ångstrom level, by carbonization of two dimensional (2D) porous sheets of pillar[6]arenes. The 2D porous sheets were prepared by 2D supramolecular polymerization induced by oxidation of hydroquinone units of pillar[6]arenes. Owing to the hexagonal structure of pillar[6]arene, the assembly induced by 2D supramolecular polymerization gave hexagonal 2D porous sheets, and the highly ordered structure of the 2D porous sheets formed regular fibrous structures.

One-dimensional channels constructed from per-hydroxylated pillar[6]arene molecules for gas and vapour adsorption.

Per-hydroxylated pillar[6]arene molecules formed highly ordered one-dimensional channels with a diameter of 6.7 Å. The channels can capture various gases, such as CO2, N2 and n-butane, and vapours of saturated hydrocarbons such as n-hexane and cyclohexane.