Nanoprecipitation of cellulose acetate using solvent/nonsolvent mixtures as dispersive media

An efficient nanoprecipitation technique using good cellulose acetate (CA) solvents as modifier for the dispersive media (nonsolvent) was developed for the generation of CA nanoparticles. Addition of tetrahydrofuran (THF) to the nonsolvent leads to smaller particles than obtained with pure water or standard stabilizing agents like surfactants and block copolymers. Sonication, efficient agitation, and optimization of process parameters like temperature, THF content, pH value and stirrer velocity reduces nanoparticle sizes and improves substrate recoveries. With the optimized process, spherical nanoparticles of 60 nm with 87% yield can be generated reproducibly. This is obtained by addition of good polymer solvents (tetrahydrofuran (THF)) to a nonsolvent (water) and applying those mixtures as nonsolvents for nanoprecipitation. Main theoretical models in discussion are not able to explain sufficiently the particle size reduction by the addition of a good polymer solvent to the nonsolvent. CA nanoparticles can be used to produce ultrathin layers deposited onto positively charged surfaces. Possible applications are seen in surface science (e.g. surface modifications and surface functionalization of CA foils and membranes).