Synthesis Of Branched And Functionalized Polyisoprenes Catalyzed By Half-sandwich Scandium Complexes

Polyisoprene is an important polymer material,which is widely used in various fields as rubber material.It is one of the largest industrial synthetic rubber materials in the world in terms of output and consumption.Compared with linear polymers,branched polymers maintain low melt and solution viscosity due to their unique branched structure.The development of rare earth isoprene rubber with branched structure will effectively realize the unification of its physical and mechanical properties and processing properties.Introduction of polar groups in the rare earth rubber materials could significantly improve the compatibility between rubber and packing and improve the physical and mechanical properties of the rubber materials at the same time.Thus,it is beneficial to improve the excellent performance of rubber materials and greatly reduce the production energy consumption of rubber materials,and promote the early realization of the great goal of carbon neutrality.The synthesis of star and hyperbranched polyisoprenes,star and hyperbranched isoprene-butadiene copolymers,linear and star aminofunctionalized styrene-isoprene-butadiene terpolymers was used half-sandwich scandium complexes as catalysts.The content of 3,4-isoprene was regulated by the selection of catalysts.This thesis compared rubber material performance of isoprene-butadiene-styrene integrated rubbers with different structures.The main results were summarized as following:(1)In(C5Me4SiMe3)Sc(CH2C6H4NMe2-o)2(Sc-1)and(C5H5)Sc(CH2C6H4NMe2-o)2(Sc2)catalytic systems,macromolecular monomers with pendent pentadienyls were prepared by the homopolymerization of dimethyl-di-2,4-pentadieneyl-(E,E)-silane(DMDPS).The mechanism of DMDPS homopolymerization was investigated by using computational chemistry.The results showed that the polymerization activity of DMDPS double bonds in Sc1 system was higher than that in Sc-2 system.In Sc-1 system star polyisoprenes were prepared by using different macromolecular monomers as the cores through "core first" method,the molecular weight of star polyisoprenes was up to 175.8×103 g/mol and the arm number of star polyisoprenes ranged from 19 to 70.The glass transition temperatures(Tgs)of star polyisoprenes could be adjusted from-1℃ to-10℃.Star isoprene-butadiene copolymers were prepared by using Sc-1 as catalyst through "core first" method.The content of isoprene in star isoprene-butadiene copolymers was proportional to its dosage,the regulation range was 20 mol%～80 mol%and the content of 3,4-isoprene in the copolymers were 65 mol%.Tgs of star isoprene-butadiene copolymers could be adjusted from-65℃ to-98℃.(2)A series of hyperbranched polyisoprene with different branching degrees were simply and efficiently prepared using the "one-pot" method with half-sandwich scandium complexes as catalysts.The content of 3,4-isoprene could be adjusted from 52 mol%to 68 mol%.The lowest branching factor g’ of hyperbranched polyisoprenes reached 0.35.The dosages of isoprene,DMDPS and catalyst effected the molecular weight and branching degree of hyperbranched polyisoprene,and the concentration of branched agent DMDPS was the most important factor.Hyperbranched polyisoprene exhibited lower viscosity in both polymer solution and melted polymer than linear polyisoprene of the same molecular weight.Hyperbranched isoprene-butadiene copolymers with different compositions were prepared by using the "one-pot" method with half-sandwich scandium complexes as catalysts.The content of isoprene in the copolymers was proportional to the corresponding feeding amount.The content of isoprene in the copolymers was in the range of 18 mol%～78 mol%.The content of 3,4-isoprene in the copolymers prepared by Sc-1 was 62 mol%.The content of 1,4-isoprene in the copolymer prepared by Sc-2 was up to 97 mol%.The glass transition temperatures of hyperbranched isoprene-butadiene copolymers varied from-58℃ to-94℃.(3)o-N,N-dimethylamine styrene(o-DMAS),m-N,N-dimethylamine styrene(m-DMAS),p-N,N-dimethylamine styrene(p-DMAS),p-N,N-diethylamine styrene(p-DEAS)could be copolymerized with isoprene and butadiene to prepare isoprene-butadiene-aminofunctionalized-styrene terpolymers in the Sc-1 system.The insertion rate of aminofunctionalized styrene was adjustable from 5 mol%to 31 mol%.The molecular weight of the terpolymers was up to 323.1×103 g/mol.The content of 3,4-isoprene in the terpolymers was 68 mol%.The glass transition temperatures of terpolymers ranged from-32℃ to-87℃.A series of star amino-functionalized styrene-butadiene-isoprene copolymers were prepared by "core first" method.The arm numbers of star terpolymers were 23 and 31.The glass transition temperatures of star terpolymers could be adjusted from-66 ℃ to-84 ℃.Isoprene-butadienestyrene integrated rubbers(SIBR)with different structure composition were designed and synthesized.CB/SIBR composites were obtained by compounding with carbon black(CB)and curing.CB/SIBR-3 containing amino-functionalized styrene had shortest vulcanization time and the best dispersion of CB.CB/SIBR-2 and CB/SIBR-3 had good wet slip resistance and high mechanical strength with tensile strength up to 10.15 MPa and 13.90 MPa,respectively.Increasing the content of 3,4-isoprene in SIBR rubber composites could improve the wet slip resistance and mechanical strength of rubber materials.And the introduction of amine functional groups could improve the dispersion of carbon black in the rubber materials,improve the mechanical strength of the materials.