EPR AND IR INVESTIGATION ON CIS-TRANS ISOMERIZATION AND OXIDATION OF POLYACETYLENE FILMS

On a étudié le mécanisme d'isomérisation du polyacétylène. Nous présentons l'évidence que l'isomérisation a lieu par la rupture d'une double liaison avec formation d'un radical et que l'oxygène catalyse cette réaction.The mechanism of polyacetylene cis-trans isomerization has been investigated. We present evidence that the isomerization takes place through the elevage of a double bond with radical formation and that oxygen catalyse this reaction

EPR AND IR INVESTIGATION ON CIS-TRANS ISOMERIZATION AND OXIDATION OF POLYACETYLENE FILMS

On a étudié le mécanisme d'isomérisation du polyacétylène. Nous présentons l'évidence que l'isomérisation a lieu par la rupture d'une double liaison avec formation d'un radical et que l'oxygène catalyse cette réaction.The mechanism of polyacetylene cis-trans isomerization has been investigated. We present evidence that the isomerization takes place through the elevage of a double bond with radical formation and that oxygen catalyse this reaction

Size and shape of sodium deoxycholate micellar aggregates

From SAXS and ESR measurements carried out on sodium deoxycholate (NaDC) aqueous solutions as a function of NaDC and NaCl concentrations and temperature we have deduced the mean hydrodynamic radius, shape, and aggregation number of the micellar aggregates. The validity of a helical model previously proposed for NaDC micellar aggregates was satisfactorily checked. Some limits of the experimental techniques are discussed. A qualitative agreement between the data obtained from SAXS and ESR measurements was observed. The extent of micellar growth increases with the concentration of added NaCl and as the temperature is lowered. Much smaller changes than for the ionic strength were detected by increasing the NaDC concentration within the range 0.05-0.15 M

Intermolecular interactions in sodium deoxycholate micelles:an NMR study involving a spin labeled cholestane

A IH and I3C NMR study of the interaction between sodium deoxycholate (NaDC) micelles and a nitroxide probe (cholestane spin-label, CSL) is presented. It is shown that CSL primarily interacts with the fi face of NaDC. The 'H NMR relaxation data enable the spatial geometry of the interaction to be defined. van der Waals energy calculations show that the CSL-NaDC interaction corresponds to a minimum if a helical model, previously proposed, is assumed for the NaDC micelle. At high concentrations of CSL, the CSL-NaDC interaction changes and the a face of NaDC may also become involved in the interaction

INTERMOLECULAR INTERACTIONS IN SODIUM DEOXYCHOLATE MICELLES - AN NMR-STUDY INVOLVING A SPIN-LABELED CHOLESTANE

A IH and I3C NMR study of the interaction between sodium deoxycholate (NaDC) micelles and a nitroxide probe (cholestane spin-label, CSL) is presented. It is shown that CSL primarily interacts with the fi face of NaDC. The 'H NMR relaxation data enable the spatial geometry of the interaction to be defined. van der Waals energy calculations show that the CSL-NaDC interaction corresponds to a minimum if a helical model, previously proposed, is assumed for the NaDC micelle. At high concentrations of CSL, the CSL-NaDC interaction changes and the a face of NaDC may also become involved in the interaction

Thermal- and UV-induced cis/trans isomerization of undoped polyacetylene films. An ESR and IR investigation

The UV- and heat-induced cis→trans isomerization of undoped polyacetylene (I) [25067-58-7] films was investigated. Temp. and UV light promote the isomerization with a similar mechanism. The formation of paramagnetic defects in trans I takes place by bond rehybridization, in agreement with previous hypotheses, and both spin concn. and spin delocalization depend on the temp. of isomerization. Under UV irradn. thermal cis→trans isomerization of I also takes place at temps. at which the sole thermal treatment isomerization is much lower or nil, so it may be possible to prep. trans-I under relatively mild conditions, leading to a better material