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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 220–240 °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’s self-stabilizability from its carboxylate groups. The effect of the polymer: LO feed ratio (1.25–3.75: 1) on the physicochemical properties of the resulting nanoparticles, e.g., colloidal stability (zeta potential > -60 mV), hydrodynamic size (300–500 nm), encapsulation efficiency (80–88%), and in vitro release, are investigated. The LO-loaded nanoparticles show non-toxicity to fibroblast cells, with an IC50 value higher than 2000 µg/mL. The products from this process have high potential as drug encapsulation templates in biomedical applications.

The role of eumelanin as a natural pigment in protecting human skin from ultraviolet (UV) light has drawn vast interest in the research and industrial community. Encapsulation of the compound by various shell materials has been extensively studied to optimize and prolong its shielding efficiency from UV penetration through the skin. Polylactide (PLA)-based copolymers have been widely used in the encapsulation of various active compounds due to their biocompatibility and biodegradability that facilitate sustained release of the active compounds. In this work, stereocomplex PLA (sc-PLA) derived from mixtures of poly(D-lactide-caprolactone-D-lactide), P(DLA-b-CL-b-DLA), a triblock copolymer with linear poly(L-lactide), and PLLA are employed to encapsulate eumelanin by an oil-in-water emulsion (O/W) technique. The effect of eumelanin distribution in PLA’s enantiomers and ultrasonication on the physicochemical properties, encapsulation efficiency, and release behavior of the nano/microparticles were evaluated. The potential application of the resulting particles for sunscreen products was assessed in terms of UV absorbance and in vitro sun protection factor (SPF). The nano/microparticles show a hollow spherical structure, whose size can be controlled by ultrasonication. The distribution of eumelanin and the ultrasonication process play a key role in the growth of sc-PLA and the crystalline structure of the particles. The highest encapsulation efficiency of 46.6% was achieved for sc-PLA2U particles. The high content of eumelanin and the hollow structure with a large surface area lead to improvement in the UV absorbance and sunscreen performance of the particles, as revealed by the increase in the SPF value from 9.7 to 16.5. The materials show high potential for various applications, especially in cosmetic and pharmaceutical fields, as UV-shielding products.