Living Coordination (Co)Polymerization of Norbornene Derivatives by Using Nickel Catalysts Derived From Bis(1,5‐Cyclooctadiene)nickel(0) and 2,6‐Dihydroxybenzoic Acid

ABSTRACT The living polymerization of norbornene (NB) was achieved using a nickel catalyst derived from Ni(cod) 2 and 2,6‐dihydroxybenzoic acid in the presence of a stoichiometric amount of trityl tetrakis(pentafluorophenyl)borate ([Ph 3 C][B(C 6 F 5 ) 4 ]) as a cocatalyst. The polymerization proceeded smoothly in toluene under mild conditions, affording polynorbornene (poly(NB)) in high yields (85%–91%), whose number average molecular weight ( M n ) was controllable in the range of M n ≤ 3.0 × 10 4 g mol −1 , keeping a relatively narrow polydispersity index ( Đ = 1.4–1.7). The living nature of the polymerization was observed when the polymerization was carried out at a lower temperature, such as 15°C, where the linear relationship was observed between the [NB]/[Ni] ratio and M n , and the post‐polymerization of NB occurred smoothly by the additional feeding of the monomer. The poly(NB) turned out to be partially insoluble under the high [NB]/[Ni] ratio (i.e., [NB]/[Ni] > 300). Furthermore, the block copolymerization of NB followed by phenylallene (PhAl) and that of PhAl followed by NB yielded well‐defined block copolymers with predictable compositions and relatively narrow polydispersity index ( Đ = 1.5–1.6), irrespective of the order of the monomer addition. The copolymers exhibited 5% weight‐loss temperature of 358°C–400°C and glass transition temperature of 83°C–87°C, depending on the ratios of each segment.