Polymerization Of Cycloolefin Catalyzed By Late Transition Metal Catalysts

Compared with the Ziegle-Natta or metallocene catalyst,the late transition metal catalyst has the advantages of easy preparation,low cost,low sensitivity to water and oxygen,and can efficiently catalyze the polymerization of olefins to synthesize polymers with adjustable structure.At present,the researches on the polymerization of cycloolefins catalyzed by late transition metal catalysts are more extensive.But relatively less research has been carried out on the polymerization of cycloolefins catalyzed by?-diimine nickel complexes.In this thesis,a series of?-diimine catalysts with novel structure and high temperature resistance were designed and synthesized.These catalysts wered used in the homopolymerization of norbornene and copolymerization of norbornene with ethylene or 1-hexene in the presence of MAO.The main results were as follows:1.Six?-diimine nickel complexes?CatA,CatB,CatC,CatD,CatE,CatF?were successfully synthesized and characterized by FT-IR and elemental analysis.2.The addition polymerizations of the norbornene were carried out by using two kinds of?-diimine nickel complexes CatA and CatB.The activity was up to 10⁵gPNB/?mol·h?at 70?.And the catalyst system reveals a relatively high activity in chlorinated solvents.The activity of CatB is significantly higher than CatA.With the increase of Aluminum and nickel molar ratio,the activity of the two catalysts increased.The thermal decomposition temperature of PNB was 450°C.3.The copolymerizations of the norbornene with ethylene were carried out by four?-diimine nickel complexes CatA,CatB,CatC and CatD.The additionamount of norbornene and ethylene have a great effect on the polymerization activity,the structure and glass transition temperature of the polymer.With the increase of norbornene content from 1.0 g to 2.0 g,the polymerization activity of CatA/MAO system increased and then decreased,and the polymerization activity of CatB/MAO system increased.In addition,polymerization temperature and aluminum-nickel ratio also have a significant effect on the polymerization activity.In the process of copolymerization,with the ethylene pressure increased from 0.1 MPa to 0.5 MPa,the activity of CatA catalyst increased from 5.81×10⁴ g·mol^-1·h^-1 to 8.87×10⁴ g·mol^-1·h^-1.The pressure of ethylene increased continuously,the catalyst activity decreased significantly.With the increase of ethylene pressure in the polymerization system,the activity of CatB decreased obviously,especially when the pressure increased from 0.5MPa to 1.0 MPa.The activity of CatB is higher than CatA at 70°C.As the ratio of n?Al?/n?Ni?increased from 800 to 1500,the activity of these two catalysts increased and then decreased.The activity of CatC decrease with the increase of ethylene pressure.The activity of CatC at 70?is 2.5 times of that at 50?.The activity of CatD is better at high temperature,butcompletely inactivated at 30?.The results show that the copolymerization of norbornene and ethylene is addition polymerization.The copolymers have better thermal stability.The T_g andtransmittance ofcoploymer decrease with the decrease of polymerization temperature and the increas ethylene content.4.The copolymerization of the norbornene and 1-hexene was carried out by CatE or CatF catalysts with the substituents of fluorine or methyl groups and orthobasic benzoyl groups.The two catalysts have good thermal stability because of the presence of the steric substituents.With the amount of comonomer 1-hexene increases,the catalytic activity decrease,but the transmittance increase.The results show that the addition-type copolymer has better thermal stability.Although the content of 1-hexene in the copolymer was less but the T_g was effectively reduced.