Takashi Kaneko

Absolute helix‐sense‐selective polymerization of an achiral acetylene monomer ( 1 ) in one‐handed helical channels created with helix‐sense‐selective decomposition of (±)‐poly 1 using circularly polarized light is realized with no chiral compounds. In addition, the relative optical yield (%ee) of the formed oligomers is controlled by those of the one‐handed helical channels.

Anthracene based phenoxyl diradicaloids are synthesized. The UV–vis spectra of them give absorption maxima around 700 nm attributes to the extended quinone structure. The diradical characters y of them are estimated as ∼0.6 from their static magnetic susceptibility and absorption maxima. The extended π‐conjugated anthracene‐linker enhances the diradical characters compared to the phenylene linker. It is noteworthy that these enhanced diradical characters are accomplished without steric effects.

Helix-sense-selective permeation (HSSPerm) of racemic helical oligoacetylenes through one-handed helical channels has been realized. The one-handed helical channels were created in the one-handed helical polyacetylene membranes by the helix-sense-selective decomposition (HSS-SCAT) of the corresponding racemic helical polyacetylene membranes, followed by removing the formed oligomers. Since the HSS-SCAT reaction proceeds with just circularly polarized visible light with no reagents, no catalysts, no solvent, and high selectivity, the chiral channel-containing membrane with high purity was obtained easily. This membrane could separate racemic helical oligoacetylenes enantioselectively in up to 30%ee. To our knowledge, this is the first example of HSSPerm.

We synthesized poly(9,10-anthryleneethynylene)s bearing benzyl ether dendrimers with alkoxy peripheral groups at the 2- and 6- positions of anthracene by polymerization of the corresponding dibromoanthracenes and bis(3-hydroxy-3-methylbutynyl)anthracenes in the presence of the Pd(PPh₃)₄ catalyst and the appropriate base. The average degree of polymerization reached DP_n = 50 by improving the solubility of poly(anthryleneethynylene)s. The UV–vis and CD spectra of poly(9,10-anthryleneethynylene)s bearing chiral menthoxy groups in addition to the dendritic side groups proved their ordered aggregation state in solution.

Oxygen/nitrogen permselective membranes play particularly important roles in fundamental scientific studies and in a number of applications in industrial chemistry, but have not yet fulfilled their full potential. Organic polymers are the main materials used for such membranes because of the possibility of using sophisticated techniques of precise molecular design and their ready processability for making thin and large self-supporting membranes. However, since the difference in the properties of oxygen and nitrogen gas molecules is quite small, for example, their kinetic diameters are 3.46 Å and 3.64 Å, respectively, the architectures of the membrane macromolecules should be designed precisely. It has been reported often that oxygen permeability (PO₂) and oxygen permselectivity (α = PO₂/PN₂) have trade-off relationships for symmetric membranes made from pure polymers. Some empirical upper bound lines have been reported in (ln α − ln PO₂) plots since Robeson reported an upper bound line in 1991 for the first time. The main purpose of this review is to discuss suitable macromolecular structures that produce excellent oxygen/nitrogen permselective membranes. For this purpose, we first searched extensively and intensively for papers which had reported α and PO₂ values through symmetric dense membranes from pure polymers. Then, we examined the chemical structures of the polymers showing the top performances in (ln α − ln PO₂) plots, using their aged performances. Furthermore, we also explored progress in the molecular design in this field by comparing the best polymers reported by 2013 and those subsequently found up to now (2020) because of the rapid outstanding growth in this period. Finally, we discussed how to improve α and PO₂ simultaneously on the basis of reported results using not only symmetric membranes of pure organic polymers but also composite asymmetric membranes containing various additives.