1 research outputs found
H‑Bonding Organocatalysts for the Living, Solvent-Free Ring-Opening Polymerization of Lactones: Toward an All-Lactones, All-Conditions Approach
The developing urea class of H-bond
donors facilitates the solvent-free
ROP of lactones at ambient and elevated temperatures, displaying enhanced
rates and control versus other known organocatalysts for ROP under
solvent-free conditions. The ROPs retain the characteristics of living
polymerizations despite solidifying prior to full conversion, and
copolymers can be accessed in a variety of architectures. One-pot
block copolymerizations of lactide and valerolactone, which had previously
been inaccessible in solution phase organocatalytic ROP, can be achieved
under these reaction conditions, and one-pot triblock copolymers are
also synthesized. For the ROP of lactide, however, thioureas remain
the more effective H-bond donating class. For all (thio)Âurea catalysts
under solvent-free conditions and in solution, the more active catalysts
are generally more controlled. A rationale for these observations
is proposed. The triclocarban (TCC) plus base systems are particularly
attractive in the context of solvent-free ROP due to their commercial
availability which could facilitate the adoption of these catalysts