Norbornene

About: Norbornene is a research topic. Over the lifetime, 5628 publications have been published within this topic receiving 104495 citations. The topic is also known as: norbornylene & norcamphene.

Propene-norbornene copolymers: Synthesis and analysis of polymer structure by 13C NMR spectroscopy and ab initio chemical shift computations

Abstract: A series of propene-norbornene (P-N) copolymers were synthesized in the presence of rac-Et(indeny)(2)ZrCl2/MAO in toluene at 30 degreesC. P-N copolymers were characterized by C-13 NMR spectroscopy, SEC, and DSC. Results were compared with those of a series of P-N copolymers synthesized in the presence of rac-Me2Si(Indenyl)(2)ZrCl2/MAO under the same experimental conditions. Polymerization activity appears to be quite low in comparison with ethene-norbornene (E-N) copolymerization. A first assignment of the main C-13 NMR signals of P-N copolymers containing isolated N units was obtained on the basis of distortionless enhancement by polarization transfer (DEPT) C-13 spectra and by comparison with isotactic polypropene (i-PP) and E-N copolymer spectra. Ab initio theoretical C-13 NMR chemical shifts, computed for the most relevant conformers of a rather simple model compound and averaged using the RIS conformer populations estimated for an isotactic chain (P-4-N)(chi), gave important detailed indications for the assignment of the complex C-13 spectra of P-N copolymers with N content up to 35 mol %. Such assignments were used to estimate the N copolymer content. The discrepancy between the values obtained from the areas of methyl signals and from the areas of the signals assigned to norbornene carbons was found to be partially due to the presence of 1,3-propene misinsertions, which are formed in significant amount when increasing the [N]/[P] ratio of the feed. Our results confirm that, despite the relatively lower polymerization activity, at low norbornene/olefin ratio it is possible to obtain P-N copolymers that are relatively richer in norbornene than the E-N copolymers prepared in similar conditions. However, at higher norbornene/olefin feed ratios the great amount of 1,3-propene misinsertions clearly reveals that the steric hindrance of the Mt-tertiary carbon bond when N is the last inserted unit makes difficult the next propene insertion, causing low polymerization activities, molecular masses, and T-g.

Olefin epoxidation catalysed by Mn(II) Schiff base complex in heterogenised–homogeneous systems

Abstract: The polymer supported Mn(II) Schiff base complexes were prepared from crosslinked chloromethylated poly(styrene-divinyl benzene) copolymer beads by sequential modification into a Schiff base bearing ligand. These Schiff base bearing polymer on treatment with a solution of MnCl 2 ·2H 2 O gave the corresponding metal complexes. The polymer supported Mn(II) complexes were characterised by elemental analysis, FT-IR, diffuse reflectance, SEM and thermogravimetric analysis. Physicochemical properties such as surface area, bulk density and swelling behaviour in different solvents were studied. The catalytic activity of the supported metal complexes were studied in the epoxidation of norbornene and cis -cyclooctene using tert -butylhydroperoxide (TBHP) as the terminal oxidant. The influence of various reaction parameters such as temperature, solvent, substrate and catalyst concentration, on conversion and selectivity has been studied.