Pyrimidine-containing poly[bis(itaconimides)]

Heat-resistant pyrimidine-containing poly[bis(itaconimides)] with a glass transition temperature of 240–250°C were synthesized via the polyaddition reaction. The film materials based on a pyrimidine-containing poly[bis(itaconimide)] and an aromatic polybenzimidazole acquired good electric and mechanical characteristics after doping with phosphoric acid.     

Thermal and dynamic mechanical properties of poly(propylene carbonate)

Summary Thermal and dynamic mechanical properties of carbon dioxide and propylene oxide alternative copolymer, poly(propylene carbonate) (PPC), and the end-capped PPC with maleic anhydride were investigated by means of TG and DMA. A master curve of the storage modulus vs. frequency can be deduced from the isochronal curves. Physical parameters of both plain and MA end-capped PPC were discussed. The results showed that for maleic anhydride (MA) end-capping PPC, an improvement of its thermal stability and mechanical properties accompanied with some modifications of the viscoelastic behavior were obtained.     

Thermal and dynamic mechanical analysis of cross-linked poly(esterurethanes)

New cross-linked poly(esterurethanes) (PEU) based on unsaturated olygo(alkyleneester)diol (OAE), 4,4’-diphenylmethane diisocyanate (MDI) and styrene or methyl methacrylate as curing monomers were prepared. The synthesis of PEU was performed in two steps. In the first step OAE was obtained from adipic acid, maleic anhydride and ethylene glycol. In the second step a prepolymer was obtained in a reaction of OAE with different amounts of 4,4’-diphenylmethane diisocyanate followed by crosslinking using previously mentioned curing monomers. The influence of structure of the poly(esterurethanes) on thermal and dynamic mechanical properties is studied. Thermogravimetric analysis shows that cross-linked poly(esterurethanes) demonstrate high thermal stability. Moreover the dynamic mechanical thermal analysis shows that the presence of styrene cross-linking chains in polymers lead to the phase separation in cross-linked poly(esterurethanes).     

Thermal decomposition of [bis(salicylaldehydato)cadmium(II)] to CdS nanocrystals

The present investigation reports, the novel synthesis of nanocrystals CdS using thermal decomposition of [bis(salicylaldehydato)cadmium(II)], as a new precursor, and elemental sulfur in oleylamine. The as-synthesized CdS crystals have diameters about 10 nm. The products were characterized by X-ray diffraction (XRD) transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–Vis) spectroscopy and Fourier transformed infrared (FT-IR) spectra. The results of this paper show that the shape and size of cadmium sulfide nanocrystals can be controlled systematically by adjusting certain reaction parameters, such as the reactant concentration, the reaction temperature and the reaction time. Cadmium sulfide nanoparticles and nanorods with different lengths have been successfully prepared.     

Thermal and dynamic mechanical relaxation behavior of stereoregular poly(2-hydroxyethyl methacrylate)

Thermal, dynamic mechanical, and dielectric relaxation techniques were used to determine the relaxation behavior of isotactic and syndiotactic poly(2-hydroxyethyl methacrylate) (pHEMA). Activation energies E_a were determined for the dielectric γ relaxation and compared with those of poly(2-methoxyethyl methacrylate) (pMEMA) to determine the influence of hydrogen bonding on side-chain relaxation processes. No difference in E_a was observed between syndiotactic pHEMA and atactic (predominantly syndiotactic) pMEMA. Isotactic pHEMA, however, had E_a + 1 kcal/mole higher than that of syndiotactic pHEMA. This was attributed to improved side-chain packing in the isotactic polymer.     

Chalcogeno[bis(phosphaalkenyl)] germanium and tin compounds

The first diphosphaalkenylstannylene stabilized through complexation with a carbene NHC-Sn[C(Cl)═PMes*](2)1 (Mes* = 2,4,6-tri-tert-butylphenyl; NHC = :C{N(iPr)C(Me)}(2)) was isolated and fully characterized including single crystal X-ray diffraction analysis. Its reaction with elemental sulfur rapidly gives the cyclic Sn(2)S(2) (dithiadistannetanne) derivative 3, presumably formed by dimerization of a stannathione intermediate. By contrast, its germanium analogue NHC-Ge[C(Cl)═PMes*](2)7 leads to the corresponding monomeric germathione 4 and germaselenone 5. The germaselenone was more stable than the germathione and could be structurally characterized. An unusual thermal cyclization reaction of the last one occurs with an excess of selenium to give the Ge(2)Se(3) (triselenadigermolane) ring derivative 6.     

Radiation induced oxidative degradation of poly[bis(p-tolylamino)] phosphazene in chlorinated hydrocarbons

Degradation induced by ionizing radiations on polyphosphazenes, dissolved in chlorinated methanes, is the subject of this investigation. Both steady gamma and pulse radiolysis techniques have been employed.The labile sites for radical attack in poly[bis(p-tolylamino)] phosphazene were identified as the aniline N-H and benzyl C-H bonds of the pendant groups. All the primary radicals, by themselves or after peroxidation, can give rise to macroradicals by hydrogen abstraction from the polymer molecules. Appreciable crosslinking appeared only in the presence of quite a high concentration of oxygen, whereas, in its absence or after it had been consumed, practically no $\text{M}{}_{\mathrm{<mtext>w</mtext>}}$ changes were detected. Optical spectra of intermediates formed after pulse radiolysis are reported and attributed to radical-polymer charge transfer complexes, anilinium ions and toluidine radicals. p-Toluidine is formed as an end-product by hydrogen abstraction from polymer molecules. In solvents where hydrogen chloride can be formed, the amino functional group is affected.     

Aromatic poly[formal-co-terephthaloyl-di(p-oxybenzoate)]s

The high-temperature polycondensation of aromatic bisphenols (phenolphthalein or diphenylolpropane) with methylene chloride in alkaline media is used to obtain oligoformals, whose interaction with terephthaloyl-di(p-oxybenzoyl) dichloride results in the formation of new copolymers with satisfactory thermal stability and resistance to some aggressive media.     

Crystal and molecular structure of bis[tetracarbonyldiphenylphosphidomanganese(0)]

The crystal structure of bis[tetracarbonyldiphenylphosphidomanganese(0)] has been determined by an X-ray diffraction study. The complex crystallizes in the monoclinic space group P2₁/n with four molecules in a unit cell of dimensions, a 15.714(4), b 16.446(5), c 12.016(4) Å, and β 101.25(2)°. The molecule has approximately centrosymmetric bi-octahedral D_2h structure. Each manganese atom is bonded to two phosphorus atoms of μ-diphenylphosphide groups and four carbonyl carbon atoms. The separation of the manganese atoms is 3.690(1) Å.     

Sorption and diffusion of organic vapors in poly[bis(trifluoroethoxy) phosphazene] and poly[bis(phenoxy)phosphazene] membranes

The sorption isotherms and diffusivities for vapors of some selected simple alcohols (methanol, ethanol, isopropanol, and 2-butanol), ketones (acetone, methyl ethyl ketone, and methyl isobutyl ketone), and aromatic compounds (benzene, toluene, and xylene) in poly[bis(trifluoroethoxy)phosphazene] (PTFEP) and poly[bis(phenoxy)phosphazene] (PPOP) were determined by integral sorption-desorption experiments at 35°C. The sorption isotherms for these compounds evaluated were almost linear to obey Henry's law for the determination of constant solubility of each solvent vapor species, and the corresponding permeabilities for them can be estimated according to the solution-diffusion model. The diffusivities for these vapors in PPOP (10⁻⁹∼10⁻⁸ cm²/s) were about one order smaller than those in PTFEP (10⁻⁸∼10⁻⁷ cm²/s) because the more rigid phenoxy groups and the higher crystallinity in PPOP may hinder the diffusion of sorbed molecules. Relatively weak dependence of diffusivity or permeability on the vapor activity (or concentration) was found, to be in contrast to the exponential dependence for many organic vapors in rubbery organic polymers, probably due to the limited increase of the free volume in sorption for these vapors in PTFEP and PPOP membranes.     

Synthesis and properties of water stable poly[bis(benzimidazobenzisoquinolinone)] ionomers for proton exchange membranes fuel cells

A novel sulfonated tetraamine, di(triethylammonium)-4,4′-bis(3,4-diaminophenoxy)biphenyl-3,3′-disulfonate (BAPBDS), was successfully synthesized by nucleophilic aromatic substitution of 4,4′-dihydroxybiphenyl with 5-chloro-2-nitroaniline, followed by sulfonation and reduction. A high-temperature polycondensation of sulfonated tetraamine, non-sulfonated tetraamine (4,4′-bis(3,4-aminophenoxy)biphenyl) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (a) or 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianydride (b) gave the poly[bis(benzimidazobenzisoquinolinones)] ionomers SPBIBI-a(x) or SPBIBI-b(x), where x refers to the molar percentage of the sulfonated tetraamine monomer. Flexible and tough membranes of high mechanical strength were obtained by solution casting and the electrolyte properties of the polymers were intensively investigated. The ionomer membranes displayed excellent dimensional and hydrolytic stabilities. Moreover, these novel membranes showed proton conductivities comparable to that of Nafion 117, especially at high temperature. In addition, the proton conductivities of the SPBIBI-a ionomer membranes were found to be higher than those of the SPBIBI-b ones due to the weakened acid–base interactions between the pyridinone ring and the sulfonic acid groups. The highest proton conductivity (0.174 S/cm) was obtained for the SPBIBI-a(100) membrane at 100 °C, with an IEC of 2.65 mequiv./g. A combination of excellent dimensional and hydrolytic stabilities indicated that the SPBIBI ionomers were good candidate materials for proton exchange membrane in fuel cell applications.     

Cyclo[bis(1,7‐naphthylenedialkylamidophosphites)]

The possibility of regioselective cyclobisphosphorylation of nonsymmetrical bisphenols was shown for the 1,7‐dihydroxynaphthalene–phosphorous acid triamide system. The structure and essential chemical properties of the first nonsymmetrical phosphacyclophane were studied. New data demonstrating peculiar features of bisphenol diamidophosphites were obtained. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:404–412, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10143     

Fabrication and spectroscopic characterization of the nanocrystals of poly[5,7-dodecadiyn-1,12-diol bis(n-butoxycarbonylmethyl urethane)]

A novel wet water–ethanol-borne technique of preparing nanocrystals of the poly[5,7-dodecadiyn-1,12-diol bis-(n-butoxycarbonylmethyl urethane)], oxoreferred to as poly(4-BCMU), is reported for the first time. The fabrication of poly(4-BCMU) nanocrystals with sizes ranging from a few to hundreds of namometers is presented. The spectroscopic analysis of the poly(4-BCMU) nanocrystals using nuclear magnetic resonance, infrared, optical absorption spectroscopy, gel permeation chromatography and scanning electron microscopic techniques is discussed. A structural characterization at molecular level of the poly(4-BCMU) constituting the nanocrystals evidences the maintenance of the molecular integrity of the polydiacetylene backbone.