Volume 43 Issue 2, February 2011

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.