Aromatic polyimides, which had trifluoromethyl group at 2,2 1 -position of the diphenyl ether, were synthesized from bis(4-amino-2-trifluoromethylphenyl)ether (1) and previously prepared tetracarboxylic dianhydrides, 3,3 111 ,4,4 111 -p-quaterphenyltetracarboxylic dianhydride (2d), 3,3 1111 ,4,4 1111 -p-quinquephenyltetracarboxylic dianhydride (2e) and 3,3 11111 ,4,4 11111 -p-sexiphenyltetracarboxylic dianhydride (2f), and the properties were compared than those of corresponding polyimides from commercially available tetracarboxylic dianhydrides. The polyimides were synthesized by the conventional two-step procedure of ring-opening polyaddition in N-methyl-2-pyrrolidinone (NMP) and subsequent thermal cyclic dehydration. The polyimides were characterized by differential scanning calorimetry (DSC), thermogravimetry, and dynamic mechanical analysis (DMA). The polyimides showed excellent thermal stability, and had glass transition temperature (T g ) at 234-300 2 C. The properties of polyimides were compared with those of previously prepared polyimides, which had phenyl group at 2,2 1 -position of the diphenyl ether, and the effect of the trifluoromethyl groups at the 2, 2 1 -positions of the diphenyl ether were observed in the thermal properties, solubility and optical properties of polyimides.

Aromatic polyimides having phenyl groups and trifluoromethyl groups at 2,2'-position of the diphenyl ether moieties have been prepared from bis(4-amino-2-biphenyl)ether (1) and bis(4-amino-2-trifluoromethylphenyl)ether (2), respectively and various tetracarboxylic dianhydrides by the conventional two-step procedure. The substituents at 2,2'-position of the diphenyl ether had a great influence on the properties of polyimides. In this paper, aromatic polyimises having only one phenyl group at 2,2'-position of the diphenyl ether moieties are prepared from 4,4'-diamino-2-phenyldiphenylether (3), and the properties are compared with those of the polyimides from 1 and 2.

Summary:An investigation has been carried out to obtain information about the effect of quenching on ethylene decomposition in the induction-coupled argon plasma jet at 1 atm. The quenching of the decomposed products was made by a small water-cooled silica tube. The lowering of the quenching temperature due to the increase in the distance between the inlet of the small silica tube and the induction coil increased the selectivity of acetylene formation on carbon base, but at the same time, the increase in the distance changed the conditions of mixing of ethylene with the plasma jet flame. The increase of the inside diameter of the small silica tube with a given outside diameter also yielded acetylene more selectively due to the drop in the quenching rate. Furthermore, it was suggested from the products distribution that the quenching of the decomposed products occurred at higher temperatures as the flow rate of argon increased. Deviation from thermodynamic equi4ibrium of the carbon-hydrogen system for composition C/H=0.5 increased with the increase in the distance between the inlet of the small silica tube and the induction coil and with the lowering of argon flow rate.

The decomposition of methane, ethane, and isobutane has been studied in an induction-coupled argon plasma jet at atmospheric pressure. Methane was decomposed to give mainly acetylene, soot, and hydrogen, and to give the traces of ethylene and ethane. From the dependence of both the conversion of methane and the product distribution on methane feed rate, the input and argon flow rate, it was concluded that methane was not completely mixed with the plasma jet but the decomposition of methane took place mainly in the outer flame of the plasma jet and its surroundings. In the decomposition of ethane, ethylene, and methane were formed in 20–27% and 3–5% selectivity based on carbon, respectively, in addition to acteylene, soot, and hydrogen. In the decomposition of isobutane, propylene was produced in 10–14% selectivity based on carbon, besides the above mentioned products. From these results together with those on propane and n-butane,it was suggested that radicals formed by a fission of C–H or C–C bond played the main role in the decomposition of saturated gaseous hydrocarbons in the induction-coupled argon plasma jet.