Synthesis of polar polynorbornenes with high dielectric relaxation strength as candidate materials for dielectric applications

Polar polynorbornenes prepared by ring-opening metathesis polymerization show thermally switchable dielectric permittivity. The polymers exhibit a large dielectric relaxation strength and high glass transition temperature.

Synthesis of highly stable dual-site immobilized ruthenium olefin metathesis catalyst without ru leaching

The tri-block copolymer is used as a carrier to simultaneously immobilize the N-heterocyclic and benzylidene ligands precursor of the Ru-based catalyst to form a dual-site immobilized catalyst. The dual-site immobilized catalyst can catalyze ring-opening metathesis polymerization, ring-closing metathesis and self-metathesis. The dual-site immobilized catalyst shows good heterogeneity in dichloromethane, which simplifies the purification of product and recovery of catalyst. The dual-site immobilized catalyst exhibits excellent activity and recycling performance. The excellent recyclability can be attributed to the capture of ruthenium by the excess ligands precursor on carrier. Importantly, ruthenium residues are not detected in product.

Mechanochemical Ring-Opening Metathesis Polymerization: Development, Scope, and Mechano-Only Copolymer Synthesis

Ruthenium-alkylidene initiated ring-opening metathesis polymerization (Ru-ROMP) was realized under solid-state conditions employing a mechanochemical ball milling method, promoting greenness and broadening scope. High-speed ball milling provided sufficient mixing and energy to the reaction mixture comprised of the catalyst and solid monomers, thus eliminating the need for solvents. Studies on the catalytic species and ball milling parameters (liquid-assisted grinding, vibration frequency, and ball size) revealed that mechanical energy regulated solid-state Ru-ROMP and it follows similar mechanistic features of solution-phase reactions. The solubility and miscibility of monomer and Ru-initiator are not a limitation in solid-state ball milling. Without the use of a solvent, a wide spectrum of solid monomers, including ionomer, fluorous monomer, and macromonomers, were successfully polymerized. Finally, effective direct copolymerization of immiscible monomers such ionic/hydrophobic and ionic/fluorous monomers resulted in a set of copolymers that are difficult to make using traditional solution procedures.