N-Heterocyclic Olefin-Based (Co)polymerization of a Challenging Monomer: Homopolymerization of ω-Pentadecalactone and Its Copolymers with γ-Butyrolactone, δ-Valerolactone, and ε-Caprolactone

A setup consisting of N-heterocylic olefins (NHOs) and several simple Lewis acids (such as MgCl2 or LiCl) was employed to homopolymerize ω-pentadecalactone (PDL) and to copolymerize it with five-, six-, and seven-membered lactones (γ-butyrolactone (GBL), δ-valerolactone (VL), and e-caprolactone (CL)). Also, the copolymerization of GBL with VL and CL was investigated separately. This dual catalytic approach succeeded for the entropically driven high-temperature polymerization of PDL in course of fast, operationally simple polymerization procedures. PPDL could be generated in short reaction times to reach high conversion (85–97%), whereby the polymerization rates are significantly modulated by the metal halide cocatalyst (ranging from virtually 0 to >80% conversion after 15 min, 1% NHO loading). Application of mildly activating Lewis acids ensured that the frequently encountered excessive transesterification was reduced to yield relatively well-controlled polyester (Mn up to 40 kg/mol, ĐM = 1.5–1.8). The 1:...