Groupes Réductifs

Sans résumé A certaines périodes durant l’élaboration de ce travail, nous avons bénéficié de l’aide financière de la N.S.F.: le premier auteur à l’Université de Chicago et à Paris (contract GP-2403), le second auteur à l’Institute for Advanced Study (contract GP-779) et à l’Université de Chicago (contract GP-574).     

Nouvelle démonstration d’un théorème de P. A. Smith

Sans résumé A Monsieur H. Hopf, à l’occasion de son soixantième anniversaire     

Synthesis and properties of new ferroelectric liquid-crystalline compounds having a tolane rigid core and an optically active alkyl sulphinate group

The synthesis and the properties of new ferroelectric liquid-crystalline compounds with a tolane rigid core and an optically active alkyl sulphinate group are reported. These compounds contain two chiral centres: a sulphinate group and a branched aliphatic chain. The two pure diastereomers having opposite configurations on the sulphur have been isolated. The mesomorphic behaviour of these two compounds is different, only one exhibiting an enantiotropic chiral smectic C phase; this clearly demonstrates the role of the sulphur configuration in determining the thermotropic properties. The mesomorphic transition temperatures, the structural behaviour as a function of temperature and preliminary measurements of the spontaneous polarization are presented.     

Microscopic investigation of ionic conductivity in alkali metal salts-poly(ethylene oxide) adducts

We present conductivity, N.M.R. and D.S.C. measurements in two P(EO) complexes : P(EO) ₈LiCF₃SO₃ and P(EO) ₁₀NaI. From N.M.R. experiments, we deduce the respective amount of crystalline and elastomeric phases at all temperatures, as well as the salt concentration in these various phases. The elastomeric phase is shown to be responsible of the ionic conductivity at all temperatures, and to be very dilute (n ? 25 just above the pure P(EO) melting point. The high melting salt-rich complexes are found surstoechiometric (n ? 3.5). The various factors affecting the temperature dependence of the conductivity are discussed, as well as the kinetics problems.