Monodisperse polymeric particles prepared by ink-jet printing: Double emulsions, hydrogels and polymer mixtures

Submerged ink-jetting produces a monodisperse emulsion that can be converted into monodisperse particles. As the initial droplet size is known and the final particle size can be easily measured, such a method can be used to quantify the shrinkage and the swelling of polymer particles made from double emulsions, polymer mixtures and hydrogel forming polymers. It is found that at the same starting concentration and initial emulsion droplet size poly-lactide-co-glycolide particles made from an ink-jetted emulsion have the same size as particles ink-jetted from a solution, however with a more porous structure. The total pore volume, however, is negligible compared to the polymer volume of the particle. If polymers containing a poly-ethylene glycol block are included, particles with internal porosity are formed, even if no double emulsion process is applied. Still the final particle size is the same. Only if typical hydrogel forming polymers are used, in which water is distributed more homogeneously, significantly higher particle diameters are found; for a four-arm PEG–poly-caprolacton a degree of swelling of 3.3 is found.