Practical polymerization of functionalized lactones and carbonates with Sn(OTf)2 in metal catalysed ring-opening polymerization methods

Abstract

We report the synthesis of functionalized polycarbonates and polyesters employing stannous(II) trifluoromethane sulfonate [Sn(OTf)₂] in homo and copolymerizations with monomers of the valerolactone family such as valerolactone and α-allyl-valerolactone using ring-opening polymerization (ROP) techniques and 5-methyl-5-allyloxycarbonyl-1,3-dioxane-2-one (MAC) and 5-methyl-5-ethyloxycarbonyl-1,3-dioxane-2-one (MEC). Practical reaction and work up conditions were established which circumvented the typically high polydispersities associated with Sn catalysts. Monomer concentration was found to be critical to incorporate challenging monomers such as α-allyl-valerolactone in the desired monomer ratios. Moreover, carbonate polymerizations were well controlled and facilitated products with narrow polydispersities. Bulk conditions for the polycarbonate polymerization were found to be preferential compared to traditional solution conditions. Additionally, the incorporation of α-allyl-valerolactone into polyester copolymers varied with monomer concentration, and highest incorporation was achieved using more dilute conditions.