Copolymerization Of Ethylene With Halogenated Styrenes And Conjugated Dienes Catalyzed By Rare-earth Catalysts

Copolymerization of ethylene with polar monomers catalyzed by transition metal complexs has always been one of the challenges in the field of polymer synthesis.The complex formed by the chelating of polar group of polar monomer with the active center of the catalyst inhibits the coordination and insertion of the double bonds of olefin monomers,thereby losing the catalytic activity of the catalyst.In addition,through the coordination copolymerization of ethylene and conjugated dienes,incorporating ethylene units in polyconjugated dienes endow the copolymers excellent physical and mechanical properties,such as improving its tensile strength and enhancing its aging resistance of.However,the catalytic activity and polymerization mechanism of ethylene and conjugated dienes are different,few catalytic systems can effectively copolymerize ethylene and conjugated dienes to form polymers with controllable sequence and stereoregularity.In this thesis,we designed and synthesized six kinds of rare-earth complexes chelated with fluorenyl ligands with different steric hindrance and electronic effects:（FluCH₂Ph）Sc（CH₂Si Me₃）₂（THF）（1）,（FluCH₂Py）Sc（CH₂Si Me₃）₂（2）（FluC₂H₄NHCMe）Sc（CH₂Si Me₃）₂（3）,（FluC₂H₄NHCⁱPr）Sc（CH₂Si Me₃）₂（4）,（FluC₂H₄NHCC₆H₂Me₃-2,4,6）Sc（CH₂Si Me₃）₂（5）,（2,7-^tBu₂FluC₂H₄NHCMe）Sc（CH₂Si Me₃）₂（6）.Copolymerization of ethylene with halogenated styrenes and conjugated dienes were studied by rare-earth precurcers 1～6.The main work is as following:（1）Rare-earth metal complexes 1,2,3,and 5 were used to copolymerization of ethylene with halogenated styrenes.Catalyst 3 achieved random copolymerization of ethylene with p FSt,p Cl St or p Br St.In the copolymers,p FSt,p Cl St,p Br St with an incorporation level of up to 46.3mol%,45.1 mol%,37.5 mol%.Increasing reaction temperatures from 20℃to 60℃results in an increment of E/p FSt copolymerization activity from 5.64×10⁵ to 8.10×10⁵ g mol _Sc^-1h^-1.In contrast,for ethylene and p Cl St,a lower temperature is beneficial to improve the E/p Cl St copolymerization activity.The random copolymerization of ethylene and p Br St can only be realized at low temperature.（2）Rare-earth metal complexes 1～6 was used to copolymerization of ethylene with butadiene.Methy-substituted N-carbine-fluorene groups constrained-geometry configuration of scandium complexes 3 showed excellent activity for the copolymerization of ethylene with butadiene,which is the most active catalytic system reported so far.The copolymerization activity reached 1.64×10⁶ g mol _Sc^-1h^-1 at 60℃under 6 atm E pressure.But 3 has low homopolymerization activity on ethylene or butadiene,indication an obvious positive comonomer effect.The butadiene content in the ethylene-butadiene copolymers is not higher than 50 mol%and the butadiene unit is mainly trans-1,4 structure.The copolymer has a high alternating sequence ethylene-trans-1,4-butadiene.The molecular weight of the copolymer is up to 20.0×10⁴ g mol^-1.Copolymers contain a certain proportion of cis-1,4,1,2 and cyclohexane units,which reduce the degree of copolymer chain regularity and the crystallinity and make it a potential rubber.the ethylene-butadiene copolymers as vulcanizates filled with carbon black has excellent tensile strength,aging resistance and puncture resistance properties.（3）The random copolymers of ethylene with isoprene and myrcene was successfully synthesized by using catalyst 3,and the copolymers have no melting peak of polyethylene segment.