Sizing down and functionalizing polylactide (PLA) resin for synthesis of PLA-based polyurethanes for use in biomedical applications

Abstract

Alcoholysis is a promising approach for upcycling postconsumer polylactide (PLA) products into valuable constituents. In addition an alcohol-acidolysis of PLA by multifunctional 2 2-bis(hydroxymethyl)propionic acid (DMPA) produces lactate oligomers with hydroxyl and carboxylic acid terminals. In this work a process for sizing down commercial PLA resin to optimum medium-sized lactate oligomers is developed at a lower cost than a bottom-up synthesis from its monomer. The microwave-assisted reaction is conveniently conducted at 220�0 ?C and pressure lower than 100 psi. The PLA resin was completely converted via alcohol-acidolysis reaction with a product purification yield as high as 93%. The resulting products are characterized by FTIR 2D-NMR 1H-NMR GPC DSC and XRD spectroscopy. The effects of PLA: DMPA feed ratios and the incorporation of 1 4-butanediol (BDO) on the structures properties and particle formability of the alcohol-acidolyzed products are examined. The products from a ratio of 12:1 which possessed optimum size and structures are used to synthesize PLA-based polyurethane (PUD) by reacting with 1 6-diisocyanatohexane (HDI). The resulting PUD is employed in encapsulating lavender essential oil (LO). Without using any surfactant stable LO-loaded nanoparticles are prepared due to the copolymer抯 self-stabilizability from its carboxylate groups. The effect of the polymer: LO feed ratio (1.25�75: 1) on the physicochemical properties of the resulting nanoparticles e.g. colloidal stability (zeta potential > -60爉V) hydrodynamic size (300�0爊m) encapsulation efficiency (80�%) and in vitro release are investigated. The LO-loaded nanoparticles show non-toxicity to fibroblast cells with an IC50 value higher than 2000�g/mL. The products from this process have high potential as drug encapsulation templates in biomedical applications. ? 2023 The Author(s).