Stabilization of non-aqueous emulsions by poly(2-vinylpyridine)-b-poly(butadiene) block copolymers

Non-aqueous sub-micron biocompatible emulsions, which are of interest for biomedical and cosmetic formulations, were developed for the system polyethylene glycol (PEG 400) dispersed in a typical liquid glycerine ester (Miglyol 812). These emulsions were stabilized by poly(2-vinylpyridine)-b-poly(butadiene) (P2VP-b-PBut) copolymers, each of these sequences being well adapted to the solubility parameters of the two liquid phases. A comparative study of the emulsifying and stabilization efficiency was performed for two copolymers with quasi-identical molecular weights but of different compositions, such as P2VP50-b-PBut128 (A) and P2VP37-b-PBut189 (B). These block copolymers form in Miglyol 812 star-like micelles having a P2VP core and a PBut corona. The PEG 400/Miglyol 812 emulsion characteristics were determined as a function of the dispersed phase volume fractions and of the copolymer concentrations. At constant concentrations, copolymer B, with longer Miglyol 812 soluble PBut chains, appeared to be more efficient as emulsifier and stabilizer than copolymer A. By combination of the two block copolymer, a synergetic emulsifying and stabilizing effect could be achieved.