A green route to synthesize poly(lactic acid)-based macromonomers in scCO2 for biodegradable nanoparticle production

Abstract

Poly(lactic acid)-based macromonomers, aimed at biomedical applications and with well-defined average chain length, are produced through catalytic ring-opening polymerization of L,L-lactide co-initiated by a co-monomer bearing a double bond. Reactions have been carried out in supercritical carbon dioxide (scCO₂) at different temperatures, ranging from 90 to 130 °C. The resulting oligomers have been characterized by different techniques (¹H-NMR, ¹³CNMR, MALDI-TOF, ESI, GPC, FT-IR, TGA), which show that oligomers with narrower molecular weight distribution are produced at the lowest temperature. In addition, a significant reduction of the impact of the secondary reactions has been found at this same temperature (90 °C), leading to a crude product with enhanced purity. Finally, the synthesized macromonomers have been used to produce NPs whose degradation behaviour has been investigated. An improved control of the degradation rate is observed for the NPs synthesized using the macromonomer produced in scCO₂ at 90 °C.