Synthesis Of Bis-(Benzocyclohexan-ketoimino) With Different Electron Groups And C-C Bridged Bis-(Salicylaldimino) Ni(?) And Their Catalytic Copolymerization For Norbornene

Through the copolymerization of norbornene and polar monomer or ?-olefin to improve the performance of addition-type polynorbornene has become the research focus,and the research of catalysts and catalytic system is the core.In this paper,four bis-?benzocyclohexan-ketoimino?Ni???complexes with different electron groups,Ni{C10H8?O?C[N?Ar?]CH3}2?Cat.1: Ar=p-PhCH3;Cat.2: Ar=p-PhOCH3;Cat.3: Ar=pPhF;Cat.4: Ar=p-PhCF3?,as well as two bis-?salicylaldimino?Ni???complexes with C-C bridged constrained geometry configuration??-Cat.1: Ni{C6H4?O?CH [N?diphenylmethyl?]}2;?-Cat.2: Ni{5-CH3C6H3?O?CH[N?diphenylmethyl?]}2?were synthesized and characterized.Homo-and copolymerization of norbornene?NB?and polar monomers?5-norbornene-2-carboxylic acid methyl ester?NB-COOCH3??,?-olefin?1-hexene,styrene?were carried out in toluene by the complexes as catalyst precursors after activated with B?C₆F₅?3,respectively.The microstructures and properties of the copolymers were characterized by means of 1H NMR?13C NMR?FT-IR?GPC?DSC?TGA and WXRD.The catalytic system Cat.1-Cat.4/B?C₆F₅?3 were used for Homo-and copolymerization of norbornene and NB-COOCH3.All complexes showed high catalytic activity toward the copolymerization?up to 2.80×105 gpolymer /molNi·h?and the activity order was Cat.4 > Cat.3 > Cat.2 > Cat.1,which illustrated the electronwithdrawing effect was beneficial to the improvement of the catalytic performance and the activity enhanced with the increase in the electron-attractive ability of the substituent.The copolymers poly?NB-co-NB-COOCH3?s were confirmed to be noncrystalline,and showed high molecular weights?up to the grade of 105?as well as narrow molecular weight distributions.The insertion ratio of NB-COOCH3 in the copolymers could be controlled by tuning the monomer feed ratios.The copolymers exhibited better solubility than that of polynorbornene and showed good thermal stability?Td >370 oC?.Well defined C-C bridged constrained geometry configuration Ni???complexes??-Cat.1,?-Cat.2?were synthesized by one-step in situ reaction.The stability of these bridged complexes was superior to that of the general bis-??-ketimino?Ni???complexes.In the presence of B?C₆F₅?3,the homopolymerization of norbornene could be achieved at a lower B/Ni molar ratio with activity up to 106 gPNB/molNi.h,and the polymerization of NB and 1-hexene was successfully achieved,the polymerization activity was about 105 gpolymer/molNi.h.The polymers showed high molecular weights?1.5-2.4×105g/mol?as well as narrow molecular weight distributions?1.62-1.89?.The obtained polymers were confirmed to be amorphous copolymer and had better solubility,good thermal stability as well as excellent optical transparency.The system ?-Cat.1,?-Cat.2/B?C₆F₅?3 were successfully realized the copolymerization of norbornene and styrene,and exhibited moderate catalytic activities.As the feed ratio of styrene increased,the catalytic activities and the Mw decreased.The molecular weight distribution of the polymers ranged from 1.71 to 2.31.The obtained polymers were confirmed to be initiated by a single active center and random norbornene-styrene copolymers,and the different monomer feed ratios had a certain effect on the microstructure of the copolymers.The solubility and processing properties of the copolymers were significantly improved compared with that of polynorbornene and showed good thermal stability and excellent optical transparency.