Liu L.,Niigata University |
Hadano S.,Center for Transdisciplinary Research |
Hadano S.,Qiqihar University |
Aoki T.,Center for Education and Research on Environmental Technology |
And 8 more authors.
Macromolecules | Year: 2010
To develop new phenylacetylene monomers more suitable for helix-sense-selective polymerization (HSSP) we reported previously and to improve the efficiency of the HSSP and membrane performance of the resulting polymers, novel phenylacetylenes having a flexible oligosiloxanyl group (SnBDHPA)together with the other related three series of monomers were synthesized and polymerized by using a chiral catalytic system and enantioselectivity in permeation of the membranes from the resulting chiral polymers were examined. SnBDHPA was the most suitable for the HSSP and the CD absorptions (G values) of poly- (SnBDHPA) were stronger and more stable than those of the corresponding polymers having rigid alkyl groups. The polymers could be fabricated to flexible self-supporting membranes by using solvent-casting method. In addition, enantioselectivity in permeation of one of poly(SnBDHPA) membranes was much higher than that of a poly(phenylacetylene) membrane having alkyl groups. This was because the polymers having oligosiloxane groups had high regularity of structures, i.e., chemical structures of the macromolecules such as one handedness and high order structures such as columnar contents in the membranes, and the membranes were flexible and had almost no defects. These good properties as optical resolution membrane materials were caused by flexibility, hydrophobicity, and bulkiness of the oligosiloxane chains. S3BDHPA having a trisiloxanyl group was found to be the best monomer for the HSSP and for obtaining good optical resolution membrane materials. © 2010 American Chemical Society.
Jia H.,Niigata University |
Jia H.,Qiqihar University |
Teraguchi M.,Niigata University |
Teraguchi M.,Center for Education and Research on Environmental Technology |
And 13 more authors.
Macromolecules | Year: 2010
Three novel chiral phenylacetylenes having an octyloxyethanolamine residue derived from a l-aminoalcohol and two hydroxymethyl groups were synthesized and polymerized by two achiral catalysts ((nbd) Rh+[Î•6-(C6H5)B -(C6H5)3] and [Rh(nbd)Cl] 2/triethylamine (TEA)) and a chiral catalytic system ([Rh(nbd)Cl]2/(S)- or (R)-phenylethylamine ((S)- or (R)-PEA)). All of the resulting polymers showed Cotton effects at wavelengths around 430 nm. This observation indicated that they had an excess of one-handed helical backbones. Positive and negative Cotton effects were observed for the polymers having an l-valinol residue produced by using (S)- and (R)-PEA as a cocatalyst, respectively, although the monomers had the same chirality. The two polymers having an l-alaninol or l-phenylalaninol residues obtained by using (S)- and (R)-PEA as a cocatalyst showed CD absorptions with identical signs. Therefore, we found that the chiral monomer having an l-valinol residue was suitable for both modes of asymmetric polymerization, that is, helix-sense-selective polymerization (HSSP) with the chiral catalytic system and asymmetric-induced polymerization (AIP) with the achiral catalysts. However, the other two monomers having an l-alaninol or l-phenylalaninol residue were not suitable for HSSP because the helix sense could not be controlled by the chirality of PEA. To explain the unexpected behaviors in the asymmetric polymerizations of the two chiral monomers having a chiral bidentate ligand, a novel third mechanism of asymmetric polymerization, that is, self-helix-sense-selective polymerization (SHSSP), is proposed in this Article. This Article discusses the contribution of the three mechanisms (AIP, HSSP, and SHSSP) in asymmetric polymerizations of the three monomers. © 2010 American Chemical Society.