Poly[p-{L-(−)-menthoxycarbonyl}phenylacetylene]s prepared by [Rh(norbornadiene)Cl]2 as a polymerization catalyst exhibited a much higher [α]D20 (= −605) than that(= −68.8) of the monomer and a very high molar ellipticity(more than 104) at the π–π* region in the CD spectrum: A chiral helical conformation of the main chain in solution is suggested. The solid membrane of this polymer showed enantioselective permeability (54%ee) for DL-tryptophan.

Recently, dendrimers have attracted much attention as the macromolecules with precisely defined threedimensional structure in organic and polymer chemistry. 1 In particular, stiff dendrimers are expected as ideal model systems for studying how physical properties depend on molecular size and architecture because the stiff dendrimers have shape persistency in comparison with flexible dendrimers. 2 The shapes of dendrimers should be significantly affected by the core group structures. Most of the synthesized dendrimers were spherical or globular, except for a few examples, 3,4 and usually showed a low viscosity, which was unfavorable for bulk materials with molding and film-forming ability. If we use a linear molecule for the core group instead of a small spot molecule, a cylindrical or rodlike macromolecule with uniform diameter will be yielded, preserving the advantage of dendrimers such as welldefined dendritic structure with many functional groups localized on the periphery of the dendrimer. For the extension of the convergent approach, the cylindrical or rodlike dendrimer should be synthesized by polymerization of a polymerizable group attached to the focal point of the monodendron, and some synthetic efforts including copolymerization were attempted by some research groups. 4 The polydendrons with a high molecular weight would also have other properties, such as membrane-forming ability, that lead to application for highly selective membranes, and the well-defined dendritic and cylindrical structure is expected to play an important role on the permselectivity.Substituted polyacetylenes can be synthesized stereoselectively by an appropriate polymerization catalyst 5,6 and have attracted attention as one of the most interesting functional polymers with electrical conductivity, 7 nonlinear optical 8 and magnetic properties, 9 and gas-selective 10 or enantioselective 11 permeability as their membrane properties. Therefore, we selected poly-(phenylacetylene) for the central core molecule and synthesized polydendrons by the polymerization of monodendrons with the phenyleneethynylene repeating unit.The monodendrons 12 were synthesized as shown in Scheme 1 by repetition of the coupling reaction of 3,5-dibromo-1-(3-hydroxy-3-methylbutynyl)benzene with the phenylacetylene derivatives of an earlier generation and the elimination reaction of a terminal acetylene-protecting group according to a modified literature procedure, 2 where (3,5-di-tert-butylphenyl)acetylene (DB0H) or [4-(trimethylsilyl)phenyl]acetylene (TMS0H) was used as the starting peripheral group to afford adequate solvent solubility. The monodendrons were polymerized with a rhodium catalyst, [Rh(C 7 H 8 )Cl] 2 , and the polymerization mixtures were purified by precipitating the chloroform solution into methanol or methanol/benzene (3/2) to yield the polydendrons 13 as yellow powders (Table 1). The rhodium catalyst has been reported to be effective for the polymerization of monosubstituted acetylenes and ineffective for disubstituted acetylenes. 6 The m...

Optical resolution of various racemates such as (±)-tryptophan and (±)-1,3-butanediol was achieved by permeation through a self-supporting membrane of (+)-poly{1-[dimethyl(10-pinanyl)silyl]-1-propyne} [(+)-poly(DPSP)] prepared by homopolymerization of (−)-1-[dimethyl(10-pinanyl)silyl]-1-propyne [(−)-DPSP]. Almost complete optical resolution (% ee of the permeate = 81−100% ee) was achieved at an initial period of concentration-driven permeation, and stable permeation with moderate permselectivity (% ee of the permeate = 12−54% ee) continued for more than 600 h. In addition, by permeation of vapor permeant such as evapomeation and pervaporation, higher permeation rates were attained maintaining high enantioselectivity. The sign of the enantiomer that predominantly permeated through a (+)-poly(DPSP) membrane was opposite to that through a (−)-poly(DPSP) membrane. In the permeation through a (+)-poly(DPSP) membrane of a solute or a solvent having a high affinity for (+)-poly(DPSP) and in the permeation through a membrane from the copolymer of (−)-DPSP with a small amount of 1-(trimethylsilyl)-1-propyne, their enantioselectivities were much lower. These findings suggest that the permeating route surrounding chiral pinanyl groups in a (+)-poly(DPSP) membrane that can enantioselectively separate various racemates was easily deformed by using a solute or solvent having a high affinity for (+)-poly(DPSP) or by removing a small amount of pinanyl groups.

Disubstituted acetylenes with chiral pinanyl groups, (-)-1-{4-[dimethyl(10-pinanyl)silyl]-phenyl}-2-phenylacetylene (1), (-)-1-{3-[dimethyl(10-pinanyl)silyl]phenyl}-2-phenylacetylene (2), (-)-1-{4-[dimethyl(10-pinanyl)silyl]phenyl}-1-propyne (3), and (-)-1-chloro-2-{4-[dimethyl(10-pinanyl)silyl]-phenyl}acetylene (4), polymerized with NbCl 5-, TaCl5-, or MoCl5-based catalysts to give high molecular weight polymers in good yields. Poly(1) and poly (2) showed intense circular dichroism (CD) effects in the UV-vis region and large optical rotations, which suggests that these polymers exist in helical conformations with an excess of one-handed screw sense. No significant decrease in the magnitude of CD effects of poly(1) and poly(2) with increasing temperature indicated the relatively high stability of their helical conformations. On the other hand, the intensities of CDs of poly(3) and poly(4) were approximately 1/10 those of poly(1) and poly (2), which means that introduction of two aromatic side groups into the repeating unit is favorable for the induction of helical conformation to disubstituted acetylene polymers. The free-standing membranes of poly(1), poly(2), and poly(3) exhibited characteristic properties as gas-permeable and optical resolution membranes.