Closing the Loop\nof Cyclopolymerization of Nonconjugated\nα,ω-Diolefin Diasteroselectivity and α‑Olefin\nPolymerization Enantioselectivity

The cyclopolymerization of α,ω-dienes catalyzed\nby\ntransition metals (TMs) is one of the most attractive synthetic routes\nfor the production of cyclic polyolefins (COPs). These COPs exhibit\nunique properties that confer enhanced performance and durability,\nmaking them highly desirable for advanced applications. By variation\nof the catalytic system, controlled microstructures of COPs can be\nachieved, particularly regarding the configuration of cyclic units\nand the cyclization ratio. The relationship between the catalyst structure,\ndiastereoselectivity, and cyclization efficiency in the cyclopolymerization\nof 1,5-hexadiene (1,5-HD) and 1,7-octadiene (1,7-OD) has been explored\nby a combined study based on the density functional theory (DFT) calculation\nand experimental study involving the synthesis and characterization\nof the resulting polymers. DFT calculations explained the <i>trans</i>-selectivity of the majority of metallocene and nonmetallocene\nsystems as well as the peculiar <i>cis</i>-selectivity of\nthe nonmetallocene pyridylamido complex for 1,5-HD polymerization.\nThe predicted diastereoselectivity was successfully corroborated by <sup>1</sup>H and <sup>13</sup>C NMR spectroscopic data collected from\nthe synthesized polymers. Analyses by WAXS and DSC and the study of\nmechanical properties were performed to investigate their structural/property\nrelationships. DFT calculations have been used also for explaining\nthe experimental switching to <i>cis</i>-selectivity for\nthe cyclopolymerization of 1,7-OD achieved by the TM systems promoting\nthe <i>trans</i>-selectivity of 1,5-HD. The comparison with\nthe enantioselectivity of α-olefin polymerization has been used\nas a key guideline for this work closing the loop between the diastereoselectivity\nof nonconjugated α,ω-diolefin cyclopolymerization and\nthe enantioselectivity of the α-olefin polymerization.