Articles in 2010

A new class of perfluorocyclobutyl poly(arylene ether)s containing 1H-1,2,3-triazoles rings were prepared. The polymer backbones and 1H-1,2,3-triazoles rings are connected by flexible oligo(ethylene oxide) side chains. The preparation process, structure and properties of these polymers of these polymers were investigated.

The maximum radial growth rate of spherulites of the novel stereocomplexationable blend of poly(L-2-hydroxybutyrate) (P(L-2HB)) and poly(D-2-hydroxybutyrate) (P(D-2HB)) was observed to be substantially higher than those of pure P(L-2HB) and P(D-2HB). The hydrolytic/thermal degradation rate of the P(L-2HB)/P(D-2HB) blend was retarded as compared with those of pure P(L-2HB) and P(D-2HB). These results indicate that the intermolecular interaction between P(L-2HB) and P(D-2HB) chains having opposite configurations was higher than that between P(L-2HB) or P(D-2HB) chains with the same configurations and are very useful for designing novel P(L-2HB)/P(D-2HB) stereocomplex-based biodegradable materials.

This paper describes the synthesis and characterization of exfoliated modified syndiotactic polystyrene/Mg–Al-layered double-hydroxide nanocomposite. Synthesized modified syndiotactic polystyrene were characterized by means of Fourier transform infrared (FT-IR) and ¹H nuclear magnetic resonance spectroscopy. The exfoliated sPS-g-(PS-b-PMS)/MgAl-LDH nanocomposite was characterized by means of FT-IR, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction and transmission electron microscopy.

Four novel poly(arylene ether)s were prepared as functional flexible films with varied morphology, remarkable thermal stability, high optical transmittance, a low dielectric constant of ∼1.9 and good mechanical property. In addition, the influence of arylene ether positions and phenyl substituents on the physical properties of fluorinated polymers was experimentally verified and provides high potential as a substrate for various flexible electronics.

The cloud points in aqueous solutions of poly(N-isopropylacrylamide) samples synthesized by aqueous redox polymerization (R) were found to be definitely higher than those of samples previously synthesized by radical polymerization using azobis(isobutyronitrile) as an initiator in tert-butanol (T) and benzene (B). Further, dependence of the cloud point on the weight-average molecular weight M_w for the R sample was found to be opposite to those for the T and B samples.

Physical gel formation of glycopolymers obtained from chemical modification of ethylene-vinyl alcohol copolymers with aminosaccharides is observed. T_gel is located in EVOH68F-Gl at slightly higher temperatures than that for EVOH56F-Gl, indicating a higher hindrance of hydrophilic interactions responsible for network formation, which are related to overall hydroxyl composition and their spatial position.

Time dependencies of the mechanical breaking stress (BS) of draglines secreted by a diurnal Nephila clavata spider and a nocturnal Yaginumia sia spider. The draglines were irradiated with UV-A* rays, which were prepared by cutting wavelengths shorter than 320 nm from a xenon-arc lamp with special filters. ○: N. clavata, •: Y. sia. In this study, the normalized BS is used by dividing the observed values of BS by the initial value before UV-A* irradiation.

The structural relaxation of glassy, spin-cast thin polymer films was investigated using spectroscopic ellipsometry. Results from poly(tertiary-butyl methacrylate) (P(tert-BMA)) and poly(normal-butyl methacrylate) (P(norm-BMA)) polymers and also blends of P(tert-BMA) and poly(methyl methacrylate) (PMMA) are compared. It is found that P(tert-BMA) films exhibit almost no relaxation over a period of several days, compared with PMMA-rich films, which exhibit significant amounts of relaxation. Blends show intermediate amounts of relaxation.

Seven novel types of acetylene monomers (PSRs) having a 4′-substituted phenyl moiety or 4′-substituted biphenyl moiety as a pendant group were synthesized from 4-oxo-4-(prop-2-ynyloxy)butanoic acid with phenol derivatives, and polymerized with the rhodium-catalyzed system. All four PSRs having 4′-substituted biphenyl moiety as a pendant group showed a liquid crystalline phase and two of these polymers showed a nematic phase.

Time dependence of ultraviolet UV-B* irradiation (prepared by excluding wavelengths shorter than 290 nm from a xenon-arc lamp) on the breaking stress (BS) and elastic limit stress (ES) of draglines (mean value±s.e.) secreted from a female Nephila clavata spider. UV-A* irradiation changed the BS markedly but the ES remained almost constant. The probability of the breaking of draglines is very high in the BS as the maximal limit of the nonlinear region, but very low in the ES as the maximal limit in the linear region. Thus, spiders could not trust all the mechanical functions of the nonlinear region. In contrast, spiders could trust the ES as they can estimate the limit in the linear region. Closed circles represent ES and open circles represent BS.

Asymmetric anionic homopolymerizations of N-substituted maleimides bearing an azo group (RMI: R=4-(phenylazo)phenyl (PAPMI), 4-(phenylazo)-1-naphthyl (PANMI)) were performed with n-BuLi or Et₂Zn—chiral ligand ((1-ethylpropylidene) bis (4-benzyl-2-oxazoline) (Bnbox) or (−)-sparteine (Sp)) complexes to obtain optically active polymers. Trans–cis photoisomerizations of poly(PAPMI) and poly(PANMI) caused by ultraviolet (UV) irradiation were observed from UV spectra. The Cotton effects for trans isomers of poly(PAPMI) and poly(PANMI) were relatively small, but those for cis isomers of poly(PAPMI) and poly(PANMI) clearly exhibited a split circular dichroism curve.

Ionic Liquids (ILs) are design solvents for free radical polymerization and preparation of composite materials! There is NO general rule for choosing of ionic solvent, but by means of design it is possible to select the best one for a concrete process. CF₃SO₃ and CF₃COO based ILs provide the formation of highest molecular weight polyacrylonitrile (PAN, M_n≈8.8 × 10⁵) and polymethylmethacrylate (PMMA, M_w≈18.9 × 10⁵) in a quantitative yield (PAN – 96%, PMMA – 92%). (CF₃CF₂)₃PF₃ ILs promote the formation of high molecular weight PMMA even upon the polymerization under the atmospheric pressure with the presence of air oxygen. Nature of the IL stongly influences the properties of the resulted composites films, namely, their flexibility, transparency and surface morphology. Composite films derived from PAN and B(CN)₄ ionic liquids possess ionic conductivity as high as 1.0 × 10⁻² S cm⁻¹ at 25°C.

Original telomers based on vinylidene fluoride were synthesized and their piezoelectric properties investigated.

The static structure of polyrotaxane (PR) possessing a supramolecular structure in which cyclic molecules are threaded into an axial polymer was investigated. Using contrast variation small-angle neutron scattering, the conformation of the axial linear polymer and the alignment of cyclic molecules within the axial polymer in a good solvent were evaluated quantitatively, together with derivation of detailed scattering theory. The entropic origin of the stiffing of PR due to the array of cyclic molecules was also discussed.

A bifunctional cobalt Salen complex containing a Lewis acid metal center and two covalent bonded Lewis base units on the ligand was designed and used for the coupling of carbon dioxide (CO₂) and epoxides at mild conditions. The Tg of the propylene oxide/cyclohexene oxide/CO₂ terpolymer can be easily adjusted between 40 and 118.9 °C.

Polyelectrolyte multilayers-modified membrane filter, leading to achieve rapid immunoassay as compared with the conventional enzyme-linked immunosorbent assay (ELISA) system. The antigen–antibody reaction was carried out by the centrifugal permeation of antigen solution allowing the local condensation of the antigen molecules in the proximity of the primary antibody. Hence, the incubation time for the antigen–antibody reaction was just permeation time, 3 min, which overcomes the molecular diffusion as rate-limiting factor compared with conventional ELISA method.

A series of poly(multidimethylsiloxane-1,4-ethynylenephenyleneethynylene)s were synthesized by condensation reactions of 1,4-diethynylbenzene magnesium reagents with various α,ω-dichlorodimethylsiloxanes. These polymers can be thermally cured to produce highly crosslinked structures. The glass transition temperatures of the cured polymers decrease with an increase in the siloxane chain length. The cured polymers are thermally stable up to almost 450 °C in both N₂ and air. The silicon oxycarbide ceramics were obtained when the cured polymers were pyrolyzed at 1200 °C under argon.

To increase the tenacity of poly L-lactic acid (PLLA), we have developed self-assembling siloxane nanoparticles with three phases: a high-density crosslinked siloxane phase (plural cores), an elastomeric silicone phase and a caprolactone oligomer phase with a high affinity for the PLLA matrix. These nanoparticles self-assemble by aggregation and condensation of an organosiloxane with three units, which respectively form each phase. Adding the nanoparticles (5 wt%) to PLLA improved the tenacity (elongation) of the PLLA without degrading its high breaking strength.

Cocrystallization phenomenon between the deuterated (D) and hydrogenated (H) species of a series of polyoxymethylene blends with various H/D ratios has been established on the basis of the detailed analysis of thermal and infrared (IR) spectral data. The melting and crystallization temperatures were found to shift continuously toward higher temperature side, with an increase of the D content. The IR spectra were found to change remarkably depending on the H/D blend content. These continuous changes have been interpreted reasonably by assuming the random arrays of the H and D chains in the crystal lattice.