Novel well-defined complex polymers, polymers of acetylenetype macromonomers having silylene−vinylene−phenylene−ethynylene hyperbranches, investigated as a new class of subnanoporous oxygen permselective membrane materials, were synthesized very easily by one-pot simultaneous twomode homopolymerization of a single monomer with a single catalyst. For this "simultaneous polymerization" we synthesized AB 2 -type monomers (1,3bis(dimethylsilyl)phenylacetylenes) containing one terminal triple bond and two Si−H groups. The resulting poly(hyperbranched macromonomer)s had high molecular weights, low densities, high solubility, and good self-membrane forming ability. They had higher oxygen permselectivities (α = P O 2 /P N 2 ) than any other reported polymers having similar oxygen permeabilities (P O 2 ). These excellent polymer membranes could be obtained only by the simultaneous polymerization. In the one-pot simultaneous polymerization, the two different modes of polymerizations, i.e., addition polymerization of the triple bond and polyaddition of the triple bond and two SiH groups in the single monomer, occurred simultaneously by using one catalytic system, i.e., [Rh(norbornadiene)Cl] 2 /various amines. The ratio of the branches (RB), i.e., the addition polymerization and the polyaddition, could be controlled by changing the amine cocatalysts. Their oxygen permselectivities could be adjusted by controlling the polymer structures including RB.

An achiral 3,5-bis(hydroxymethyl)phenylacetylene connected with a rigid and π-conjugated substituent was polymerized using a rhodium (Rh) complex catalyst in the presence of chiral 1-phenylethylamines. The circular dichroism (CD) spectra of the polymers indicated that an excess of one-handed helical polyacetylene backbone was induced by helix-sense-selective polymerization under the asymmetric conditions despite the achiral monomer. The split-type-induced CD signals at 300 nm were attributed to the chromophore including the conjugated side group since the signal appeared at a longer wavelength than the poly[3,5-bis(hydroxymethyl)phenylacetylene] without conjugated substituent.

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.

We synthesized new 3,5-bis(hydroxymethyl)phenylacetylene (HPA) monomers connected with a rigid and linear π-conjugated oligomer. The monomers were successfully polymerized with a rhodium catalyst [Rh(nbd)Cl]2 in the presence of chiral PEA to give the corresponding polymers. Helix-sense-selective polymerization proceeded for DBHPA. CD, UV, and WAXS spectroscopic studies revealed that the intramolecular hydrogen bonds of the polymers contributed to the stabilization of their helical conformation but the stability depended on the length of the rigid and linear π-conjugated side group.

Four kinds of newly synthesized achiral phenylacetylenes bearing a phenylhydrogalvinoxyl residue at 4-position were polymerized by using a chiral rhodium catalyst system, [Rh(nbd)B(C6H5)4] or [Rh(nbd)Cl]2 catalysts in the presence of chiral (R)-(+)- or (S)-(–)-1-phenylethylamine ((R)- or (S)-PEA) cocatalysts. Poly(m-HGDHPA) and poly(m-HGTHPA) in THF showed Cotton signals at the absorption regions of the main chain and hydrogalvinoxyl in the circular dichroism (CD) spectra. It indicated that excess of one-handed helical polyacetylene backbone was induced by helix-sense-selective polymerization (HSSP) under the asymmetric conditions despite the achiral monomer, and the hydrogalvinoxyl moieties were also arranged to form one-handed helical structure. However, there was no Cotton effect for poly(p-HGDHPA) and poly(p-HGTHPA) because the intramolecular hydrogen bonding did not act well to stabilize the helical conformation. The hydrogalvinoxyl units of poly(m-HGDHPA) and poly(m-HGTHPA) were converted to the corresponding galvinoxyl radicals after treatment with PbO2. In the CD spectra of the polyradicals, the Cotton effects decreased depending on their static stability of helical conformation, suggesting that reversal conformation of the polymer chain arose.