Wilhelm Risse

Pd2+ catalyzed addition polymerizations of norbornene and norbornene derivatives

Abstract Cationic Pd2+ complexes were used for the preparation of poly(2,3-bicyclo[2.2.1] hept-2-ene), a saturated polymer with the bicyclic structure of the monomer left intact. The polymer was characterized by thermal analyses and molecular weight determinations. Samples with narrow molecular weight distributions (polydispersities Mw/Mn, as low as 1.07) were prepared with the initiator [Pd(CH3CN)4][BF4]2. Polymer chain growth of this addition polymer was found to continue after renewed monomer addition, indicating rare chain transfer and chain termination.

Transition metal catalysed metathesis polymerizations of partially fluorinated norbornene derivatives

Abstract Ring-opening olefin metathesis polymerization (ROMP) of partially fluorinated norbornene derivatives with a catalyst based on WCl6 gave amorphous poly(1,3-cyclopentenylene vinylene) derivatives with high glass transition temperatures, low indices of refraction and good oxidative and thermal stability. The influence of the substitution pattern on monomer reactivities and polymer properties was investigated. Exo-substituted monomers were found to be more reactive than the corresponding endo isomers.

Controlled carbocationic polymerizations of bicyclo[2,2,1]hepta-2,5-diene with AlCl3 in the presence of electron pair donor components†

The cationic isomerization polymerization of bicyclo[2.2.1]hepta-2,5-diene (norbornadiene) was investigated. The synthesis of gel-free poly(3,5-tricyclo[2.2.1.0 2,6 ]heptylene) was achieved at a reaction temperature of 0°C. These polymerizations were initiated by AlCl 3 in the presence of the weakly donating additives nitrobenzene or nitromethane. NMR spectra show that the polymer contains a small fraction (between 2 and 4 mol-%) of branched structures in addition to a small amount of 5,7-linked bicyclic olefin units (approximately 2%). A reaction mechanism involving non-classical carbocation intermediates is proposed in order to account for the 5,7-enchainment of the bicycloheptenylene units, which contrasts with earlier studies on cationic norbornadiene polymerizations. Further, pentamethylbenzene was utilized as a chain transfer reagent in order to adjust the number average molecular weight M n to values below 2500.