Hydrogel Nanoparticles by Inverse-Miniemulsion Polymerization and Supercritical CO2 Drying

Hydrogel nanoparticles can be successfully produced by polymerization in inverse miniemulsions, for use in a variety of applications including diagnosis, drug delivery, separation, and absorption. Unfortunately, conventional drying techniques result in particle agglomeration due to the sticky nature of the wet hydrogel particles. This work utilizes supercritical CO2 drying to obtain free flowing dry hydrogel nanoparticles. Using inverse miniemulsion technique (cyclohexane continuous phase, water dispersed phase, and a non-ionic surfactant), nanoparticles (500 nm diameter) of polyacrylamide are produced. The polymerized miniemulsion is injected into supercritical CO2 which results in rapid removal of cyclohexane, water, and surfactant. The morphology, particle size and size distribution of the nanoparticles are determined using dynamic light scattering and scanning electron microscopy. The effect of supercritical CO2 flow on the drying efficiency is examined and compared with via freeze-drying and spray-drying techniques. Dry nanoparticles obtained from of supercritical CO2 drying show much lower agglomeration.