Role of dispersion stabilizer with hydroxy groups in preparation of monodisperse polylactide microspheres

Monodisperse poly(D,L-lactide) (PDLLA) microspheres were prepared by dispersion polymerization of D,L-lactide in xylene/heptane (1/2, v/v) with poly[(dodecyl methacrylate)-co-(2-hydroxyethyl methacrylate)] (P(DMA-co-HEMA)) as a dispersion stabilizer. P(DMA-co-HEMA) contains hydroxy groups, which act as an initiation group for pseudoanionic dispersion polymerization. The best coefficient of variation (CV) values concerning particle diameter distribution and the particle diameter of obtained PDLLA microspheres were 3.7% and 5.3 μm, respectively. The particle diameter decreased with increasing concentration of P(DMA-co-HEMA) and HEMA maintained low CV (<10%) values. As a result, monodisperse PDLLA microspheres ranging from 1.3 to 5.3 μm were obtained. In addition, it was found that monodisperse PDLLA microspheres were obtained by sufficient capture of growing polymers and monomers in the particle growth stage. Therefore, the HEMA concentration in P(DMA-co-HEMA) strongly affecting the capturing capability is the most important factor. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5230–5240, 2009