Multiple and Co-Nanoprecipitation Studies of Branched Hydrophobic Copolymers and A–B Amphiphilic Block Copolymers, Allowing Rapid Formation of Sterically Stabilized Nanoparticles in Aqueous Media

Nanopreciptation of hydrophobic polymers into aqueous media is still a relatively poorly understood phenomenon. Here we present the first model studies of branched vinyl polymer nanoprecipitation and the co-nanoprecipitation of the branched polymers with linear amphiphilic A–B block copolymers. The instantaneous formation of nanoprecipitates is shown after addition of polymers in a good solvent to the aqueous antisolvent, and the limits of the solvent mixtures are determined. Multiple nanoprecipitations are also shown to be possible through direct addition of polymer solutions to aqueous nanoparticle dispersions after solvent removal, leading to particle concentration increase without modification of the initial nanoprecipitate size. When nanoprecipitation of branched polymer/A–B block copolymer mixtures were studied, variation of the ratio of the two polymer architectures led to varying z-average diameters, narrow particle size distributions, tunable stability to salt addition and storage within aqueous salt conditions. A mechanistic rationale was investigated using a simplified classical DLVO approach, and the impact of branched copolymer:A–B block copolymer ratio is discussed.