Synthesis and gas barrier characterization of poly(ethylene isophthalate)

Poly(ethylene isophthalate) (PEI) was synthesized for this research with essentially a condensation polymerization of isophthalic acid and ethylene glycol catalyzed by zinc acetate and antimony trioxide. Several samples were obtained, and their characteristics were observed and compared with poly(ethylene terephthalate) (PET). The synthesized PEI samples were chemically identified by ¹H NMR. Thermal analysis with differential scanning calorimetry (DSC) yielded results that indicate the samples were primarily amorphous, with a glass‐transition temperature of 55–60 °C. Molecular weights of these PEI samples were also obtained through intrinsic viscosity measurements (Mark–Houwink equation). Molecular weights varied with conditions of the polymerization, and the highest molecular weight achieved was 21,000 g/mol. Finally, the diffusion coefficient, solubility, and permeability of CO₂ gas in PEI were measured and found to be substantially lower than in PET, as anticipated from their isomeric chemical structures. This is because in PET the phenyl rings are substituted in the para (1,4) positions, which allows for their facile flipping, effectively permitting gases to pass through. However, the meta‐substituted phenyl rings in PEI do not permit such ring flipping, and thus PEI may be more suitable for barrier applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4247–4254, 2004     

Inaccessible hydroxyl groups on silica are accessible in supercritical CO2

The three main types of hydroxyl groups on a silica surface are classified as isolated, hydrogen bonded, and inaccessible. The isolated and hydrogen bonded groups are the most important as these readily exchange with D(2)O and thus are exposed to reactant molecules. However, it has generally been accepted that the inaccessible groups do not participate in surface reactions as only a small fraction of these groups exchange with D(2)O. It is shown that the inaccessible hydroxyl groups on nonporous fumed silica and mesoporous MCM-48 silica powders and films fully exchange with D(2)O and are reactive with octadecylydimethylchlorosilane when supercritical CO(2) is used as the solvent. Furthermore, it is found that the CO(2) penetrating the regions containing the inaccessible groups is not removed by simple evacuation but rather slowly diffuses from the silica over periods of months.     

EPR evidence for 17O− on molybdenum oxide supported by silica-gel

The EPR spectrum of ¹⁷O^? on partially reduced molybdenum oxide supported on silica-gel has been observed following adsorption of N₂O at room temperature. The spectrum is chracterized by g_⊥=2.019 and g_|=2.002 with a_|¹⁷O^?=96±1 G and a_|⁹⁵MO,⁹⁷MO=7.5±0.5 G. The O ^?ion appears to undergo exchange with oxide ions at the surface.     

Über Sauerstoffperowskite des fünfwertigen Rutheniums ABIIIRuVO6 mit AII = Ba,Sr

On Oxygen Perovskites with Pentavalent Ruthenium A B^IIIRu^VO₆ with A^II = Ba, Sr The perovskites Ba₂B^IIIRu^VO₆ with B^III = La, Nd, Sm, Eu, Gd, Dy, Y, are cubic (B^III = La: a = 8,54₄ Å; Y: a = 8,33₇ Å); with a partial order for B^III and Ru^V. The Sc compound, Ba₂ScRuO₆, has a hexagonal 6 L structure (a = 5.79₅ Å; c = 14.22₉ Å; sequence (hcc)₂)₂. The lattice of the Sr perovskites, Sr₂B^IIIRu^VO₆, with B^III = Eu, Gd, Dy, Y is rhombic distorted. The IR and FRI spectra are discussed.     

Synthesis, Structure and Conductivity of the New Charge-transfer Salt (ET)_2(CH_2=CH-CH_2-SO_3)·H_2O

ET is one of the most famous electron-donor molecules, which forms charge-transfer complexes (abbr. CT-complexes) with various types of counterions. These complexes have received intense attention because a wide range of physical properties such as conductivity and superconductivity1, ferromagnetism2-4 and nonlinear optical properties5 was found in these materials. Although the majority of the ET-based CT-complexes were prepared by combining with inorganic counterions, CT-complexes with o…     

A theoretical interpretation of isotope effects in mixtures of light and heavy water—II

Solvent isotope effects for H₂O---D₂O mixtures and for ionic hydration equilibria in such mixtures can be calculated from the structure difference between D₂O and H₂O and that between HDO and H₂O and the relative amounts of the three waters. The behavior of acids in H₂O---D₂O mixtures is considered in detail. Dissociation constants of acetic acid are calculated over the complete range of deuterium concentrations and found to agree with the experimentally determined ones. The Gross equation for the dependence of isotope effect on mole fraction of deuterium for acid-catalyzed reaction of substrates S proceeding via SL⁺ transition states (L=H or D) is derived from first principles.