Polystyrenes with p-oligo-siloxane,silane, germanosiloxane,germane, or stannane as p-substituents as materials for oxygen permeable membranes

The title polymers were synthesized and the oxygen permeation behavior through the polymer films were studied. The oligodimethylsilane-substituted polystyrenes showed a little low Po₂ compared with the oligodimethylsiloxane-substituted polystyrenes. The important role of trimethylsiloxyl group in permeation was suggested.     

Syntheses of helical polymers through the combination of axially dissymmetric segments

Wholly aromatic polymers with various helical structures were prepared through the combination of two axially dissymmetric bifunctional compounds. The palladium-catalyzed condensation of (R)-2,2-diethoxy-6,6′-dibromo-1,1′-binaphthyl with (R)-1,1′-binaphthyl-2,2′-diamine and the reaction of (S)-2,2-diethoxy-6,6′-dibromo-1,1′-binaphthyl with (S)-1,1′-binaphthyl-2,2′-diamine produced helical polyamines, and the chiral conformation was confirmed by their circular dichroism spectra and large specific rotations. The combination of (R)-2,2-diethoxy-6,6′-dibromo-1,1′-binaphthyl and (S)-1,1′-binaphthyl-2,2′-diamine afforded polyamines with a zigzag conformation. The condensation of (R)-2,2′-dimethylbiphenyl-6,6′-dicarbonyl chloride with (R)-2,2′-diamino-6,6′-dimethylbiphenyl and the reaction of (S)-2,2′-dimethylbiphenyl-6,6′-dicarbonyl chloride with (S)-2,2′-diamino-6,6′-dimethylbiphenyl predominantly yielded cyclic dimers and tetramers because of the steric proximity of the reactive groups of the propagating species. The experimental results indicated that the structures of the obtained polymers depended on the combination of the chirality of the bifunctional atropisomeric compounds and the position of the functional groups on the aromatic rings. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4607–4620, 2004     

Block copolymerization. V. Block anionic polymerization of lactams

Bischloroformates of hydroxy-terminated poly(tetramethylene glycol) (PTG) and polystyrene (PSt) were prepared and used as the initiators for the anionic polymerization of α-pyrrolidone and ε-caprolactam in bulk at 30°C and 80°C, respectively. Initiation efficiency was sufficiently high to give well-defined nylon–PTG(or PSt)–nylon block copolymers. Both the yield and the viscosity of the block copolymer increased with polymerization time up to 50% conversion of the lactam.     

Block copolymerization. VII. Kinetic studies on the polymerization of pivalolactone with polystyrene dicarboxylates and polyacrylonitrile dicarboxylates

The rate of anionic polymerization of pivalolactone with polystyrene dicarboxylates decreased with conversion, suggesting deactivation of the propagating chain end by precipitation of the polymer during polymerization. The presence of unreacted initiator was explained by slow initiation for formation of a living polymer of pivalolactone. Various factors affecting block efficiency were discussed, and high efficiency was obtained for the preparation of block copolymers containing a long pivalolactone segment by using more nucleophilic polystyrene dicarboxylates. Block copolymer of acrylonitrile and pivalolactone was prepared from polyacrylonitrile dicarboxylates.     

Synthesis of an immunomodulator (+)-conagenin and its analogs

Stereoselective synthesis of an immunomodulator (+)-conagenin was achieved. Both amine and carboxylic acid moieties were prepared from commercially available optically active methyl 3-hydroxy-2-methylpropanoate using dirhodium(II)-catalyzed C-H amination and chelation-controlled reductions as key steps. In addition, demethyl analogs of conagenin were synthesized using similar procedures.     

Polystyrenes with structurally different oligosiloxanes as p-substituents for oxygen permeable membrane materials

Polystyrenes with structurally different oligosiloxanes as p-substituents were synthesized and the selective oxygen permeation through the polymer film was studied. It was found that the structure of the p-oligosiloxane substituents had great effects not only on the glass transition temperature of the polymer but also on the oxygen permeation behavior through the polymer film. Trimethylsiloxyl groups, especially, were shown to play an essential role in enhancing the permeability.     

Morphological evolution of inorganic crystal into zigzag and helical architectures with an exquisite association of polymer: a novel approach for morphological complexity

The morphology of potassium sulfate (K(2)SO(4)) crystals grown in a viscous polymer solution of poly(acrylic acid) (PAA) was remarkably changed from the tilted columnar assembly into zigzag and helical architectures with increasing PAA concentration. The habit modification of orthorhombic K(2)SO(4) with adsorption of PAA molecules on a specified crystal face fundamentally led to the formation of tilted unit crystals. Concurrently with the habit modification, a diffusion-limited condition controlling the assembly of tilted units was achieved in the presence of PAA molecules in the matrix. Various complex morphologies, including zigzag and helical assembly, emerged through the formation of twinned crystals with the variation of the diffusion condition. Understanding the morphogenesis observed in this report would provide a novel approach for sophisticated crystal design by using an exquisite association of organic and inorganic materials.