Fluorinated poly(benzoxazole–imide)s

New poly(benzoxazole–imide)s have been prepared by polycondensation of bis(o-aminophenol)s, such as 3,3′ dihydroxybenzidine or 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane, with diacid chlorides containing both imide and hexafluoroisopropylidene groups. The soluble polymer precursor resulting from the first step of polycondensation in N-methylpyrrolidinone (NMP) at low temperature was processed into thin flexible films, which were then thermally treated to reach the fully cyclized structure of poly(benzoxazole–imide)s, as observed by infrared spectra. An alternative way to produce the cyclization was by heating at reflux the solution of polymer precursor in NMP. Thermal stability, glass transition temperature, dielectric constant and its dependence on relative humidity have been studied and compared with those of related polybenzoxazoles and other heterocyclic Polymers.     

Synthese und Struktur von η2,η2-Butadien-bis[η2-butadien-(2,2′-bipyridyl)nickel(0)]

The title compound (III) was prepared by reaction of trisethenenickel(0) (II), 2,2-bipyridyl and butadiene at –40°C in the form of dark grey-green crystals with a metallic luster. The structure was determined by X-ray crystallography.

Röntgenstrukturanalyse.     

Gültigkeitsbegriffe für Gleichungen in partiellen Algebren

Ohne Zusammenfassung