Manipulation of process parameters to achieve different ternary phase microparticle configurations

Ternary phase microparticles of poly( d, l-lactide-co-glycolide) (50:50), poly( l-lactide) and poly(caprolactone) were fabricated through a one-step solvent evaporation technique. The purpose of this study was to examine the effects of various process parameters on the final configuration (i.e. polymer distribution and dimensions) of these composite microparticles and, subsequently, propose their mechanism of formation. Particle morphologies and configurations were determined using scanning electron microscopy, polymer dissolution tests and Raman mapping. It was found that a starting polymer solution prepared below the cloud point and an increased oil to water ratio will facilitate polymer configurations close to thermodynamic equilibrium, which is dictated by the interfacial energies of the components. By varying the polymer mass ratio or adjusting the precipitation rate, through stirring speed and oil to water ratio, a wide range of microparticles with different core–shell dimensions and embedded particulate sizes can also be fabricated. At the same time, lowering the polymer solution concentration and increasing the stirring speed may result in smaller microparticles. Correlation of these process parameters with the final composite particle morphology was thus established. This understanding should allow the controlled fabrication of ternary phase composite microparticles through a single step solvent evaporation technique.