Polyethylene oxide (PEO) has been applied to industrial or biological use as a highly hydrophilic, viscous and spinnable polymer. So far, the mixed system of PEO-H2O has been discussed in various articles. 1-3 A powder sample of PEO, on the other hand, has a high degree of crystallinity, so that its hygroscopicity is as low as about 5% at 80% RH, which is very low among hydrophilic polymers. 4 However, once PEO powder is mixed with hydroquinone (HQ) powder, its hygroscopicity is remarkably increased, although HQ itself does not show any hygroscopic character. Water molecules absorbed during the mixing process are linked between the oxygen atom of PEO and the hydrogen atom of HQ by hydrogen bond. The water molecules in this case, are considered to exist in quite a different bound state from bulk water. 5 In this paper, we discuss the various states of water molecules restricted by PEO, using DSC, NMR and HFS (high-frequency spectroscopy). ExperimentalMaterials and sample preparation: The weight-average molecular weight of PEO used in this study was 70000 (Wako Pure Chemical Industries, Ltd.). Pure water and/or heavy water was mixed with the PEO powder in various molar ratios. Instruments1 H NMR spectra were obtained using a JEOL EX400 operated at 400 MHz, at 25˚C. DSC analysis was carried out by a SEIKO Exstar6000 DSC120C, DSC100. After each sample was sealed in a silver metal container and carefully weighed (about 10 mg), it was first cooled to -120˚C at a rate of 4˚C/min, and then the temperature was raised to 80˚C at a rate of 4˚C/min. Measurement of the high-frequency spectra was conducted using the measuring system previously reported, 6-8 in the frequency range 0 -2000 MHz at room temperature. Results and Discussion PEO-H2O systemPEO-H2O systems in various molar ratios of EO (constitutional repeating unit of PEO) to H2O were investigated by DSC, in order to know the behavior of water molecules interacting with PEO in biological or industrial processes. The water molecules species contained in PEO are divided roughly into two species of freezable water and non-freezable water from temperature and enthalpy for melting/crystallization. The former is not significantly different from bulk water and may be called "weakly bound water". The latter exhibits large differences from bulk water in melting enthalpy and temperature, and may be called "strongly bound water". No phase transition can be observed in DSC measurements. Figure 1 shows the DSC curves obtained for the samples of PEO-H2O system. In case of the sample with the molar ratio 0.5 of H2O to EO, a melting peak of bound water is observed near -8˚C, while PEO shows two melting peaks around 50˚C, which is somewhat lower than the melting point of pure PEO. Furthermore, in the samples with the molar ratio more than 1.0, the intensity of the melting peak becomes weaker, showing that the crystallinity of PEO reduces, that is, the extent of amorphous part increases. Figure 2 shows the NMR spectra for the samples of PEO-H2O and PEO-D2O systems recorded at 25˚C jus...

Oxidation of iso-butane was studied using metal pyrophosphate catalysts and it was found that iso-butene was formed with 82% selectivity over Ni2P2O7 at 550 °C. Zn2P2O7, Cr4(P2O7)3, and Mg2P2O7 showed 60–70% iso-butene selectivity. and 9–22% selectivity to CO and CO2. Deep oxidation into CO and CO2 was promoted over Cu2P2O7 and Sn2P2O7 Only small amounts of oxygenated products such as alcohols, aldehydes, ketones, and carboxylic acids were formed over every catalyst.

No abstract

No abstract

Abstract-In the system of polyimide(PI)/metal, the oxidation of meta at both metal surface and PI/metal interface and the diffusion of metal to PI were infered from PBS measurement and TENM observation. These were enhanced by curing in some cases.The