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This paper is related to the phase separation of different copolyesters of lactides and glycolide solutions induced by the addition of silicone oil in order to promote microencapsulation of proteins. This coating process can be divided in three successive steps: phase separation of the coating polymer; adsorption of the coacervate droplets around the drug phase, and microcapsule solidification. This paper focuses on the physico‐chemical analysis of the second step. The knowledge of the interfacial tensions between the three liquid phases allows understanding of the microscopic evolution of the phase separation medium.

This paper deals with protein microencapsulation by coacervation of poly(1actide-co-glycolide) solutions in CH,Cl, induced by the addition of silicone oils of various viscosities.This coating technique proceeds along three steps : phase separation of the coating polyester, adsorption of the coacervate droplets around the protein phase, and hardening of microparticles. Size distribution, surface morphology and internal porosity of the final microspheres clearly depend on the main characteristics of the coacervate, particularly the viscosity, in a direct connection with the CH,Cl, content. Indeed, the whole porosity (which may be as high as 80%), average pore size and broadness of pore size distribution decrease as the coacervate is more viscous. Hardening of the coacervate droplets is thus so fast that the organic solvent is entrapped within the polymer matrix and predetermines the internal porosity. Finally, size distribution of microspheres is bimodal in a clear relation with the coacervate viscosity. A less viscous coacervate favours smaller microspheres (within the 7-90 pm range), contaminated with a minor population of microparticles below 4 pm.

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