مرکز منطقه ای اطلاع رساني علوم و فناوري -

چكيده لاتين :

Cyclopentene is known to undergo equilibrium polymerization through a metathesis reaction which its bulk and solution polymerizations have been thoroughly investigated. However, we have found that under specific experimental conditions, this monomer polymerizes in the gas phase. The gas phase polymerization is defined here as the conversion of pure gaseous monomer into polymer in the condensed phase. Pure gaseous cyclopentene is found to polymerize on a glass surface in the upper part of the ampoule above the liquid phase when the polymerization is initiated with only tungsten hexachloride. Polymerizations are carried out under high vacuum and in the 10-60°C temperature range. In presence of methanol, the colourless formed polymer shrinks slightly, then it can be removed easily from the glass surface and simply dried under vacuum without any other purification process. From kinetic measurements, an overall activation energy of 63.47 kJ/mol is obtained for the conversion of one mole of gaseous monomer to one unit of condensed polymer. GPC Chromatograms of polymer samples are compared with chromatograms of polystyrene standards obtained in the same conditions in chloroform. All polymer chromatograms show a narrow molar mass distribution. Elution peaks of the polymer correspond to peaks obtained for the standards with high molar mass ranging from 2x104 to above 2x10 6 g/mol. 1H NMR Spectra at 200 MHz show no loss of double bonds in the polymer, nor any presence of tertiary proton. This Key Words: results indicate that the polymer is linear and branching or cross-linking, if present, cancyclopentene; not be detected. Spectra obtained through 13CNMR spectrometry at 22.63MHz allow the ROMP; determination of the proportion of cis and trans configurations.