Study on the Reaction Probability of Double Bonds in Polybutadiene Through Olefin Metathesis

Abstract Olefin metathesis is a powerful technique for modifying diene‐based polymers but is limited by low catalytic efficiency and poor structure controllability due to unclear reaction probabilities between main‐chain and side‐chain double bonds. Using polybutadiene with 65–95% 1,2‐unit content and Grubbs 1st catalyst, we demonstrate that main‐chain double bonds react preferentially over side‐chain ones, enabling higher degradation efficiency at lower 1,2‐unit contents. Trace water in nonpolar n‐hexane doubled degradation efficiency by promoting 1,4‐unit reactivity. For polymers with < 5% 1,4‐unit content, metal carbene transfers to 1,4‐units via vinyl groups, facilitating degradation. This transfer process induces five‐membered ring formation through ring‐closing metathesis between adjacent vinyl groups. Polar solvents enhance vinyl group reactivity, increasing cyclization degree to 21%. These findings advance the controlled modification of diene‐based polymers via olefin metathesis.