PLA-based nanoparticles with tunable hydrophobicity and degradation kinetics

In this work, the preparation of poly(lactic acid) (PLA)-based degradable nanoparticles (NPs) with tunable hydrophobicity and degradation kinetics via starved emulsion free-radical polymerization is studied. The synthesis of macromonomers, constituted of a tunable number of lactic acid units functionalized with 2-hydroxyethyl methacrylate (HEMA), has been performed via bulk ring opening polymerization (ROP) of L, L-lactide catalyzed with 2-ethylhexanoic acid tin (II) salt. Macromonomers were characterized through SEC, NMR, and FTIR and are subsequently polymerized through monomer-starved semi-batch emulsion polymerization (MSSEP). The effect on the polymerization process of various emulsifiers on the final diameter and particle size distribution has been studied. The resulting PLA-based NPs are characterized by a narrow size distribution and a small particle size, down to 25 nm. Finally, a degradation study of selected NPs has been carried out to verify their degradability in aqueous media. It has been demonstrated the complete degradability of these PLA-based NPs which occurs upon the hydrolysis of the PLA pendant chains leaving poly-HEMA chains, which, being hydrophilic causes the NPs to dissolve in the aqueous suspension. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012