Dual control of stereoregularity and molecular weight in cationic polymerization of vinyl ether by tunable TADDOLs/TiCl4 initiating systems

The effects of aryl substituents on α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL) ligands were investigated to develop a TADDOL/TiCl4 system that simultaneously controls the stereoregularity and molecular weight of poly(isobutyl vinyl ether). Substituents were appropriately designed to generate polymers with relatively high m values (80–90%) and narrow molecular weight distributions (Mw/Mn = 1.1–1.4) at 0 °C and −78 °C. The steric and electronic effects of TADDOL substituents on the stereoregularity and molecular weight were investigated. Interestingly, conventional fast equilibrium between the dormant C–Cl bonds and active species was likely absent at −78 °C, while the polymerization was mediated by long-lived species, resulting in a linear increase in molecular weights with monomer consumption. This study provides significant insight for the development of high-performance polymerization catalysts through which multiple polymer structures can be simultaneously controlled.