Because lactic acid is a chiral molecule, three different forms
of PLA, namely, PLLA, PDLA, and PDLLA, exist. Adding
nanofillers to semicrystalline polymers such as PLLA and
PDLA may change their crystallization behavior, leading to
mechanical property changes. We chose the amorphous
PDLLA in this work to eliminate the nucleation factor from
the analysis. In the solvent evaporation technique, PLA is first
dissolved in a volatile organic solvent to form the oil phase,
which is then emulsified with a high-speed mixer into a
continuous water phase as discrete oil droplets. A suitable
surfactant is used to stabilize the emulsion. The organic solvent
is then evaporated from the emulsion under stirring to let the
oil droplets harden to form microparticles.
42,43
The diameters
of the particles obtained varied widely, ranging from about 150
nm to more than 1μm (Figure 2). A nonuniform particle size
distribution is common in drug microencapsulation using this
technique.
42
Although polymer particles with near-uniform
sizes below