Articles in 2012

Recent work is reviewed in which nanoporous polyethylene, derived from a polymeric bicontinuous microemulsion, is used as a nanocasting template in the synthesis of a catalogue of porous materials, including ceramics, thermosets, conducting polymers, and hierarchical inorganic and organic materials. Their structures replicate that of the bicontinuous microemulsion precursor with high fidelity, resulting in disordered and three-dimensionally continuous arrangements of multiple phases having a characteristic length scale of ∼100 nm.

Copolymerization of polydimethylsiloxane (PDMS) macromer having two molecular weight (M_n), two types of methacrylate and crosslinker was conducted. The crosslinked copolymer was analyzed with ¹³C solid-state NMR to investigate the relationship between copolymers compositions and physical properies by molecular level approach. The T₁^H, T_1ρ^H, and T_1ρ^c values suggested the influence of PDMS M_n and methacrylate type on microstructure, mobility, and morphology change. Thus the present analysis contributes to a better understanding of the physical characteristics on the crosslinked methacrylates-siloxane copolymers.

The effect of the viscosity of polycarbonate (PC) matrix on the thermal conductivity of PC/vapor-grown carbon fiber (VGCF) composite was investigated in terms of the rheological properties of PC/VGCF. Thermal conductivity of low viscosity PC increased with contents of VGCF in spite of adding the same amount of VGCF. From the result of the rheological properties which were originated in the network structure, we clarified that the dense network of VGCF could be formed in lower viscosity matrix.

Poly(2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[def]phenanthrene)) (PCPP) is a stable blue light emitting conjugated polymer even after annealing at 150 °C or operation of the device in air. The polymers, BC-PCPP, CO-PCPP and BO-PCPP, have been synthesized by Yamamoto polymerization. The photoluminescence (PL) emission spectra of the BC-PCPP, CO-PCPP and BO-PCPP in chloroform solution show maximum peaks at 398, 387 and 384 nm, respectively. The polymer films show maximum peaks at 419, 425 and 425 and additional peaks at around 530 nm in PL spectra.

Poly(acrylic acid) (PAAc) gel particles with DNA–ethidium bromide (EtBr) was synthesized and pH-sensitivity and fluorescence property were evaluated for applying to optical micro-pH sensor. Swelling ratio of PAAc gel particles with DNA–EtBr complexes were regularly changed with pH and the gel particle responded to pH for about 60 s. Furthermore, fluorescence intensity of PAAc gel particles with DNA–EtBr complexes were detected with high-sensitivity and changed in response to pH as shown in figure (The left shows the gel particles in pH 2.1 and the right shows in pH 11).

This figure reveals the relationship between the area of the conducting parts and the volume resistivity changed with CPP–SO₃H content. The PP/CPP–SO₃H/PANI composites’ area of the conducting parts is much higher than the PP/CPP/PANI 0 composite’s area, and volume resistivity of the PP/CPP–SO₃H/PANI composites is much lower than that of the PP/CPP/PANI 0 composite. These may elucidate that the introduction of the –SO₃H on CPP can increase the area of the conducting parts of the composite, improve the compatibility between PP and PANI-DBSA and decrease volume resistivity of the composite.

Imidazole-terminated first- and second-generations poly(amidoamine)-typed POSS-core dendrimers denoted as POSS-Im16 and POSS-Im32, respectively, were synthesized. The results of pH titrations for the dendrimers showed well-defined one-step titration curves as same as that of 1-methylimidazole as a monomeric imidazole compound. Spectrophotometric titrations of the dendrimer aqueous solutions with Cu²⁺ ions indicated variation of the coordination modes of POSS-Im16 from the Cu²⁺–N₂O₂ complex to the Cu²⁺–N₄ complex and the existence of the only one complexation mode of Cu²⁺–N₄ between Cu²⁺ ion and POSS-Im32 with increasing concentrations of the dendrimers.

Biologically identified peptides that bind to the surfaces of isotactic poly(methyl methacrylate) (PMMA), syndiotactic PMMA, and their assembled stereocomplex films were used as noncovalent surface modifiers. Each peptide was biotinylated and immobilized onto the PMMA films to function as a linker for the subsequent immobilization of streptavidin. We demonstrated that the PMMA species had a great impact on the peptides' abilities to functionally modify the film surfaces.

Perylene diimide (PDI) derivatives with cyclodextrins (PDI-CD₂s) exhibit specific emission properties, which depend on the type of CDs in an aqueous solution. Herein we create an emission from film kneaded PDI-CD₂s derivatives via effective tumbling of the altropyranose unit. We have observed the selective emission of PDIC₇-3βCD₂ in aqueous solutions and prepared emission films kneaded into polyvinyl alcohol (PVA) films. The emission depends on the cavity size of the altro-CDs formed through altro-CD tumbling.

Transmission electron microscopy of epoxy nanocomposites with process parameters of clay loading of 2.0 wt%, magnetic stirring time of 120 min and sonication time of 30 min showed good intercalation morphology. The glass fiber-based composites containing epoxy and clay mixture with these parameters produced maximum Young's modulus.

Photomobile polymer fiber was prepared from a mixture of commercially available compounds. The fiber was bent toward the light source upon exposure to UV light. Addition of a low-molecular weight liquid-crystalline compound enhanced the photomechanical properties and photoreactivity.

A series of racemic helical or achiral poly(phenylacetylene)s were prepared, and the preferential helical sense of the polymers was induced by transformation in chiral solvents, even if the interaction between the chiral molecule and the polymer was weak such as solvent–solute interaction. The enantioenriched helical poly(phenylacetylene)s possessing no chiral moieties except for helicity were obtained by removal of chiral solvents. In particular, one of them retained the induced helical sense even in an achiral solvent.

Liquid crystal polymer (LCP) nanofibers were prepared by electrospinning from isotropic and biphasic poly(γ-benzyl-L-glutamate) (PBLG)/dichloromethane-pyridine solutions. The as-spun PBLG fiber from the isotropic solutions had an undulating orientation of closed packed α-helices like a serpentine trajectory. The as-spun fibers from the biphasic solutions containing the LC phase, on the other hand, had uniaxially oriented hexagonal lattices of α-helices along the fiber axis. These results indicated that the orientation of the ordered structure of the electrospun lyotropic LCP fibers can be controlled by the initial microstructure of the spinning solution.

Pd-catalyzed Suzuki coupling polymerization of macrocycle-containing monomer with diboric acid pinacol esters afforded aromatic poly(ether ketone)s with optically active macrocycles. The resulting aromatic poly(ether ketone)s have high glass transition temperatures (T_g: 220–257°C), large molar rotations ([Φ]_D²⁵: +1906–1976 deg) and excellent solubility to typical solvents such as CHCl₃ and DMF.

We demonstrated that a method based on the analysis of both orientational birefringence and photoelastic birefringence is effective for designing polymers that are processed in a molten state and used in a glassy state. The designed polymer exhibits no birefringence for any orientation of the polymer main chains or under elastic deformation. Birefringence is close to zero even in injection-molded plates of the polymer. We have also shown that it is possible to compensate and control the birefringence of polymers using inorganic nanocrystals, and we have obtained valuable information on the optimal size of nanocrystals for compensation and control of birefringence.