Ruthenium–Carbene Complexes in the Synthesis of Polybutadiene and Its Cross-Metathesis with Polynorbornene

The activity of known and newly synthesized Ru-carbene catalysts in the metathesis polymerization of 1,5-cyclooctadiene and interchain cross-metathesis of synthesized polybutadiene with polynorbornenes is studied. First- and second-generation Grubbs Ru-complexes, second-generation Hoveyda–Grubbs complexes, and their modified analogs with asymmetric fluoro-containing ligands and unsaturated imidazolyl moieties are used as catalysts. It is shown that in the presence of the second-generation modified and nonmodified catalysts a partially crystalline polybutadiene is formed, in which blocks with trans-С=С bonds are about four times longer than blocks containing cis-С=С bonds. In the case of catalysts with bulkier ligands, the length of trans blocks is smaller and the melting temperature of the polymer is lower. The activities of the catalysts are compared by in situ ¹Н NMR monitoring. New norbornene-butadiene multiblock copolymers are prepared for the first time by cross-metathesis between polybutadiene and polynorbornene. The highest degree of blockiness of the copolymers is attained when using second-generation Grubbs and Hoveyda–Grubbs catalysts. The activity sequences for the studied catalysts are constructed. It is shown that macromolecular cross-metathesis occurs more intensively in the presence of the catalysts with less bulky ligands.