Synthesis of uniform submicron poly(lactic acid)-based particles/capsules by radical precipitation polymerization

Poly(l-lactic acid) (PLLA) is a well-known biopolymer, usually synthesized via step-growth or ring-opening polymerization from lactic acid or a lactide monomer, respectively. PLLA microspherical particles are produced by dispersion polymerization with a ring-opening lactide monomer using a particular copolymer chain as a stabilizer. This is not easy to achieve when dehydration is needed. Here, a robust and simple synthesis of a nearly monodisperse, submicron PLLA-based particle/capsule was proposed via radical precipitation polymerization without the use of surfactant. A commercial PLLA was first glycolyzed with ethylene glycol to obtain a low molecular weight glycolyzed PLLA (GPLLA). Then, the GPLLA was copolymerized with methacrylic acid and ethylene glycol dimethacrylate monomers using a benzoyl peroxide initiator. Active sites on the GPLLA backbone were generated by hydrogen abstraction of benzoyloxy radicals that further copolymerized before self-assembly to form the polymer particles. Uniform particle size of about 580 nm with a low polydispersity index (PDI) of 0.012 was obtained. This method was also implemented to produce nearly monodisperse capsules containing linalool. The particle size of PLLA-based capsules was about 280 nm with narrow particle size distribution (PDI of 0.120). The PLLA-based capsules effectively inhibited microbial growth of Staphylococcus aureus, Escherichia coli and Candida albicans and were not toxic to human cells.

Automated summary

A novel method for preparing PLLA particles and capsules without the use of surfactant was proposed in this study. The nearly monodisperse products showed excellent inhibitory effects on microbial growth and were non-toxic to human cells.