Dibutyl phosphate catalyzed commercial relevant ring-opening polymerizations to bio-based polyesters

Organocatalyzed ring-opening polymerization (ROP) of cyclic esters was developed into a stage that demanding translation of the academic success into commercially viable production. An industrial relevant development of the organocatalysis in ROPs required bulk polymerizations at high temperatures up to 180 °C. Organic phosphoric acid was one of the few organocatalysts workable under these conditions that devoid of otherwise commonly appeared transesterification, epimerization, and decarboxylation in the ROPs. A commercial dibutyl phosphate (DBuP), which was inexpensive and available by hundreds of tons as antistatic agent, was firstly evaluated as a catalyst. Well-defined polyesters catalyzed by DBuP were obtained with narrow dispersities (Đ _m 1.08–1.31) and predicted molecular weights from 2.1 to 55 kg mol ⁻¹ . Series of homopolymers, diblock copolymers and end-functionalized polymers of ε-caprolactone (CL), δ-valerolactone (VL), trimethylene carbonate (TMC), and L-lactide (LA) were synthesized. ¹ H NMR, ¹³ C NMR, SEC, and MALDI–ToF MS analyses indicated that the obtained polyesters were exactly the designated ones. NMR titration experiments confirmed that the ROP proceeded a bifunctional activation mechanism. The cytotoxicity test using MTT assay showed biosafety of the polyesters. The experimental results suggested that dibutyl phosphate is a commercial organocatalyst widely useful in all major cyclic ester monomer toward commercial relevant ring-opening polymerizations.