Homo- And Copolymerization Of Norbornene Catalyzed By Bidentate Titanium Complexes

Norbornene?NBE?is a special monomer which contains double bond and ring structure.It can be polymerized by vinyl-type addition polymerization,ring-opening metathesis polymerization and free radical/cationic polymerization.The vinyl-type PNBE has many excellent properties,such as high transparence,low birefringence and low dielectric loss,which can be used in many fields.In order to improve the processability of vinyl-type PNBE,a-olefin monomers are usually imported into the polymerization system of NBE to get the cyclo olefin copolymer?COC?.Recently,the research about NBE polymerization have forced on the developing of new catalytic system and new copolymerization system.Here,the[N,O]and[N,N]bidentate titanium complexes were used for the homopolymerization of NBE,as well as the copolymerization of NBE with 1-cotene?OC?,1,3-butadiene?BD?and isoprene?IP?respectively.The influence of reaction conditions on the polymerization was explored and the polymers were characterized by different measurements.The[N,0]bidentate titanium complex?SF-Ti?was used for the homopolymerization of NBE,with aluminum alkyl and Ph₃CB?C₆F₅?₄ as cocatalyst.When AliBu₃ was used as cocatalyst,the optimun reactive condition was summarized as follows:[Ti]/[Al]/[B]=1:5:1,[NBE]/[Ti]=200:1,polymerized in toluene at 60? for 4 h.As a result,the polymer yield reached up to 72.2%and the activity was 3.39×103 gpNBE/?molTi h??However,when AlEt3 replaced AliBu₃ in the catalytic system,the polymer yield reduced to 59.9%with an activity about 1.88×103 gPNBE/?molTi h?at the same reactive conditions.PNBE was proved to be a vinyl-type polymer by 1H NMR at 125?,and possessed an excellent thermal stability?Td?440 ??.SF-Ti/AliBu₃/Ph₃CB?C₆F₅?₄ ternary catalytic system was applied for the copolymerization of NBE with OC,geting a random copolymer.The weight-average molecular weight?Mw?of copolymer was about 1.3-4.5×10⁴ g/mol,with a molecular weight distribution index between 1.91-2.45.The reactivity ratios of NBE and OC were 3.01 and 0.08 respectively.The NBE content in copolymer could be adjusted by the feed ratio of two monomers.The glass-transition temperature?Tg?and thermal decomposition temperature?Td?of the copolymer were detected at 50-70 ? and 300 ?respectively controlled by the content of NBE in copolymer.SF-Ti/AliBu₃ binary system showed high activity to the copolymerization of NBE with BD.The optimun reactive conditions were summarized as follows:[Al]/[Ti]=7:1,[Monomer]/[Ti]=200:1,[NBE]/[BD]=5:5,polymerized in toluene at 40 ? for 6 h.The copolymer was prepared with number-average molecular weight about 0.2-1.3×10⁴ g/mol and moderate molecular weight distribution?MWD=2-2.2?at 91%yield.The result of DEPT 135 13C NMR identified the vinyl-type polymerization of NBE in the copolymer.The content of NBE in the copolymer almost kept in a constant level?55%?,in spite of varying the polymerization conditions,monomer feeding ratio and conversion,which revealed the alternative structure in the backbone of copolymer.The copolymer had a low Tg?50-70 ??and high Td?380 ??,as well as excellent transparency under the visible light.The[N,N]bidentate titanium complex?SNN-Ti?achieved the homopolymerization of NBE as well as the copolymerization of NBE and IP with AliBu₃ as cocatalyst.With the reactive condition of[Al]/[Ti]=5:1,[NBE]/[Ti]=200:1,polymerized in toluene at 100 ? for 6 h,the vinyl-type PBNE yield reached up to 62.1%.The Mw of PNBE was about 4.5-6.8×10⁴ g/mol and MWD between 1.39-2.03.The copolymerization of NBE and IP required a mild reactive condition.Polymerized at 40 ? for 6 h,the copolymer yield reached up to 97.9%.Varying the reactive conditions,the copolymers possessed a similar composition ratio,which indicated the alternate structure of the copolymer.The NBE units in the copolymer were vinyl-type structure and the vast majority of isoprene occupied 1,4 structure.The copolymer possessed only one Tg between 65-82 ? and exhibited high thermal stability with a Td above 300 ?.The thin film of copolymer had an excellent transparency under the visible light.The click reaction between copolymer and mercapto derivatives could import hydroxy and carboxyl into the backbone achieving a novel kind of polar polymer.