Dielectric properties of addition and metathesis polynorbornenes with bulky side-substituents

© 2020 Elsevier Ltd Structure-property study of polynorbornenes for low dielectric permittivity materials was performed. Dielectric properties of various polynorbornenes bearing F-, Si- and alkenyl-side groups were investigated. The incorporation of both fluoroorganic- and Me3Si-groups as side substituents was found to be a fruitful tool to tune dielectric properties and to obtain polymeric materials with low values of dielectric relative permittivity (hereinafter dielectric permittivity) and the dissipation factors. Addition polynorbornenes with Me3Si- or alkenyl-side groups disclosed dielectric permittivity in the range of 2.07–2.34. Polynorbornenes containing fluouroorganic groups exhibited dielectric permittivity as low as 1.94–2.78. To the best of our knowledge, the achieved values of dielectric permittivity are the lowest ones among published for polynorbornenes. The investigated polymers also exhibited low or moderate values of the dissipation factor. The obtained results are considered and discussed along with the data of wide-angle X-ray diffraction, positron annihilating lifetime spectroscopy, low temperature nitrogen adsorption/desorption investigations

Solvent-free Buchwald–Hartwig amination with low palladium loadings

A highly efficient ‘green’ solvent-free monoarylation of primary anilines with aryl bromides mediated by the expanded-ring N-heterocyclic carbene palladium complex (THP-Dipp)Pd(cinn)Cl [THP-Dipp is 1,3-bis(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene; cinn is cinnamyl] can be performed at low catalyst loadings (0.1 mol%) to provide excellent yields and remarkable selectivities for various substrates. © 201

Solvent-free Buchwald–Hartwig amination with low palladium loadings

A highly efficient ‘green’ solvent-free monoarylation of primary anilines with aryl bromides mediated by the expanded-ring N-heterocyclic carbene palladium complex (THP-Dipp)Pd(cinn)Cl [THP-Dipp is 1,3-bis(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene; cinn is cinnamyl] can be performed at low catalyst loadings (0.1 mol%) to provide excellent yields and remarkable selectivities for various substrates. © 201