Water dispersibility of non-aqueous emulsions stabilized and viscosified by a poly(butadiene)-poly(2-vinylpyridine)-poly(ethylene oxide) (PBut-P2VP-PEO) triblock copolymer

Biocompatible non-aqueous emulsions, stabilized by a well-defined poly(butadiene)-poly(2-vinylpyridine)-poly(ethylene oxide) (PBut-P2VP-PEO) triblock copolymer, were developed for the system glycerine ester (Miglyol 812) dispersed in polyethylene glycol (PEG 400). One of the most attractive features of this copolymer is its capacity to form, by hydrogen bonding, thermoreversible micellar systems in PEG 400 with a thermal transition around 43 °C. Moreover, this transition was also observed in the case of a non-aqueous viscosified emulsion, with 30 vol% Miglyol 812 as dispersed phase. An original aspect of this type of emulsions, with a water-miscible PEG 400 continuous phase, is its water dispersibility at pH 1 and pH 7 without any additional surfactant. In fact, the initial non-aqueous emulsion is sterically stabilized and after water addition at pH 1 the copolymer provides a combination of steric and electro-steric stabilization due to the presence of the PEO sequences and of the protonated P2VP units. At pH 7, the stabilization is predominately achieved by the PEO and, to a lesser extent, by the collapsed P2VP sequences. The electro-steric stabilization at pH 1 is more efficient than the steric stabilization at pH 7.