1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD), N-methyl-TBD (MTBD), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) are effective organocatalysts for the ring-opening polymerization (ROP) of cyclic esters
such as lactide (LA), δ-valerolactone (VL), and ε-caprolactone (CL). TBD is shown to polymerize LA, VL, and
CL in a fast and controlled manner, whereas MTBD and DBU polymerized LA and addition of a thiourea cocatalyst
led to the ROP of VL and CL being achieved. Each of the catalysts produced polymers displaying high end
group fidelity, good correlation between theoretical and observed molecular weight, and linear relationships between
conversion and molecular weight. The enhanced activity of TBD relative to MTBD and DBU is attributed to its
bifunctionality, enabling the simultaneous activation of both the cyclic ester monomer and the alcohol group of
the initiator/propagating species. Temperature-dependent NMR studies generated individual association constants
for MTBD with benzyl alcohol and thiourea with VL. In combination with temperature-dependent ROP of VL
in the presence of benzyl alcohol, MTBD, and thiourea, these data have led to the derivation of the activation
energy for the ROP (49 ± 3 kJ mol-1). The simplicity of the reaction conditions, the ready availability of the
catalysts, the variety of polymerizable cyclic ester monomers, and the exquisite control over the polymerization
are demonstrated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.