Homo-and Copolymerization Of Norbornene Catalvzed By Rare Earth And Titanium Based Catalvsts

As one of the most reactive strained cyclic olefin, bicyclo[2.2.1]hept-2-ene (norbornene, NBE) can be polymerized by cationic polymerization, ring-opening metathesis polymerization (ROMP) and vinyl-type addition. PNBE obtained by both ROMP and vinyl-type addition has many attractive properties and can be used as potential materials. In this paper, the homopolymerization of norbornene and the copolymerization of norbornene with isoprene by rare earth catalysts or titanium complex were studied. The influences of reaction conditions on the polymerization, polymerization kinetics and mechanism were investigated. The structure and the properties of polymers obtained were characterized, too.Investigation of the homopolymer of norbornene prepared with scandium phosphonate catalyst using alkylaluminium as cocatalyst showed that PNBE obtained were of the ring-opened type in most cases, but also showed ring-retention to varying degrees in this type of catalyst system. Catalyzed by Sc(P204)3/AlEt3or Sc(P507)3/AlEt3under the optimal polymerization conditions producing a polymer with high yield, part soluble in organic solvents. Catalyzed by Sc(P204)3/Ali-Bu3system producing a insoluble and crosslink polymer with low yield.Vinyl-addition type polymerization of norbornene was successfully carried out using a rare earth catalytic system composed of rare earth complex and tri-isobutyl aluminum with trityl tetra(pentafluorophenyl)borate as the third component for the first time. Sc(P204)3/Ali-Bu3/trityl tetra(pentafluorophenyl)borate system was found efficiently for the vinyl-addition polymerization of norbornene.Copolymerization of norbornene with isoprene catalyzed by traditional Ziegler-Natta system composed of TiCl4and Al(i-Bu)3was studied. The PNBE-co-IP copolymers obtained have relatively narrow molecular weight distribution, and soluble in common organic solvents. The influences of catalyst composition, polymerization conditions, and the monomer feeding ratio on the copolymerization were investigated. The NBE content in copolymer can be controlled in the range of 26-60%by varying the feeding ratio of comonomer. and the Tg of the copolymer increased with the increasing of NBE content in copolymer. The microstructures of the obtained copolymers were confirmed by1H-NMR and DEPT13513C-NMR, and indicate that the NBE monomers undergo an addition-type polymerization during the copolymerization with isoprene. The reactivity ratio of two monomers were determined by the Kelen-Tudos method.High light transmittance copolymers with high molecular weights, good solubility and low glass transition temperature were successfully prepared using bis[N,N-(3,5-di-tert-butylsalicylidene)anilinato] titanium(IV) dichloride and triisobutyl aluminum catalytic system in toluene. NMR analysis confirmed that NBE was polymerized through a vinyl-addition type polymerization, and the IP units were1,4-addition in the copolymer. The resulting copolymer exhibits not only high thermal stability for the induce of vinyl-add norbornene but also has lower Tg for the existence of isoprene-C=C-bonds. The copolymerization of NBE with IP can also be catalyzed by bis[N,N-(3,5-di-tert-butylsalicylidene)anilinato] titanium(â…£) dichloride and MAO. But the copolymer obtained by this system is crosslinked and insoluble in organic solvents.