Catalytic copolymerization of ethylene with various olefins in solution and in emulsion.

摘要

The copolymers of ethylene with both, polar and non-polar olefins were obtained in solution and in emulsion catalytic polymerizations, using Ni- and Pd-based catalysts. Latexes of copolymers of hexadecene or undecenol and ethylene were prepared by emulsion polymerization using a Ni-based catalyst formed in-situ. These latexes may form polymeric films upon evaporation of water. Film adhesion may be improved by introducing undecenol units. Norbornene was copolymerized with ethylene in organic solution and in aqueous emulsion using ill-defined Pd-based sulfonated arylphophine catalytic systems. Norbornene incorporation could be as high as 45 mol. %, leading to copolymers which are alternating. The copolymers with > 15 mol. % of norbornene were suitable for the formation of solvent-based coatings. The resulting films were assessed for anticorrosion properties by EIS after treatment in a Q-Fog chamber.;With this catalyst in hand, copolymers of ethylene with either N-vinyl-2-pyrrolidinone (NVP) or N-isopropylacrylamide (NIPAM) were prepared directly from the corresponding comonomers. The microstructure of the copolymers was characterized by 1H and 13C NMR, IR and differential scanning calorimetry. These linear copolymers are shown to combine a high melting point with a low contact angle with water -- a fact which could potentially open the door to a directly paintable linear polyethylene.;Using the same catalyst, ethylene was copolymerized with acrylates in solution and in emulsion. The kinetics of the solvent based copolymerization of C2H4 and methyl acrylate were found to be limited by the reaction of pyridine substitution and by the sigma-coordination of the acrylate on Pd. The substitution of pyridine by itself was shown to proceed via an associative mechanism with activation parameters DeltaH≠ = 16.8 kJ/mol and DeltaS≠ = -98 J/(mol K), whereas the activation parameters for the substitution of pyridine by methyl acrylate were found to be DeltaH≠ = 18.1 kJ/mol and DeltaS ≠ = -87 J/(mol K). Using these Pd-based catalysts in an emulsion polymerization process, latexes of copolymers of ethylene with various acrylates having particle diameters ∼200 nm were obtained. Their solid contents did not exceed 5% because of the low activity of the catalyst resulting from the coordination of water and resulting from the slow decomposition of the active site by water.;Keywords: copolymerization, organometallic catalysts, polyethylene, polyolefins, catalytic polymerization, miniemulsion polymerization, polymer films, latex, anticorrosion coating, acrylate copolymers, norbornene copolymers.;Several well-defined Pd-based catalysts were prepared for the copolymerization of ethylene with polar monomers. Reaction of (2-[bis-(2-methoxy-phenyl)-phosphanyl]-4-methyl-benzenesulfonic acid and 2-[bis-(2',6'-dimethoxy-biphenyl-2-yl)-phosphanyl]-benzenesulfonic acid with dimethyl(N,N,N',N'-tetramethylethylenediamine)-palladium(II), PdMe2(TMEDA) led to the formation of TMEDA bridged palladium based polymerizalion catalysts. Upon reaction with pyridine, two mononuclear catalysts were isolated. These catalysts were found to homopolymerize ethylene and also copolymerize ethylene with acrylates or with norbornenes. With the ligand 2-[bis-(2',6'-dimethoxybiphenyl-2-yl)-phosphanyl]-benzenesulfonic acid, high molecular weight polymers were formed in high yield. Higher comonomer incorporations were obtained with catalyst having the (2-[bis-(2-methoxy-phenyl)-phosphanyl]-4-methyl-benzenesulfonic acid ligand.