Ring opening metathesis copolymerization of norbornene with norbornadiene from solutions with different mole fractions of the comonomers catalyzed by Ru-amine complexes

Copolymers from norbornene (NBE) with norbornadiene (NBD) were synthesized via ring opening metathesis copolymerization varying the mole fractions of the comonomers (0.8: 0.2; 0.6: 0.4; 0.4: 0.6; 0.2: 0.8) for a total monomer quantity of 5000 equivalents/[Ru]. The batch reactions were performed with [RuCl ₂(PPh₃)₂(amine)] complex types as precatalysts, where amine is perhydroazepine (1) or piperidine (2), in CHCl₃ (2 mL) in the presence of ethyl diazoacetate (5 μL) for different intervals of times (5, 30, 60, and 120 min) at 40°C. The copolymers were characterized by ¹³C NMR. Quantitative yields of isolated materials were obtained from solutions with NBD: NBE 0.8: 0.2 mole fraction in the presence of 1, decreasing to 70% for NBD: NBE 0.2: 0.8 solutions. Concerning 2, the yields were 70% at most. Polymeric materials obtained with 1 were less soluble in CHCl ₃ than those synthesized with 2. The dependence of the reaction yields and occurrence of crosslinking on the starting NBE: NBD proportion related to reactivity of the complexes 1 and 2 were discussed. A few differences in the amines such as ancillary ligands were sufficient to change the reactivity of the {RuCl₂(PPh₃)} moiety complex to provide copolymers with different compositions.