(217au) Synthesis and Optimization of Polymer Micelles Formed Via Electrospray-Enabled Interfacial Instability

The development and use of nanoparticles is an important area of national research focus. Here, we describe a promising method to synthesize functionalized nanoparticles that combines electrospray and an interfacial instability process to form micelle structures from amphiphilic block copolymers. In this process, block copolymers in an organic phase are introduced to an aqueous solution  and micron sized emulsion droplets form. Transient interfacial surface tension changes then result in micelle formation. 

Previously, micelle production via interfacial instability was performed in a batch process. Here, we describe a scaled-up approach using electrospray to generate the emulsion droplets. A coaxial electrospray process generates the emulsion and spherical micelles form from poly(styrene-block-ethylene oxide) (PS-b-PEO). The micelles can be “empty” or loaded with functional nanoparticles such as quantum dots (QDs) or superparamagnetic iron oxide nanoparticles (SPIONs). The micelles are ~30-40 nm in diameter. 

To control the size and number of micelles produced in the electrospray synthesis approach, the effect of electrospray synthesis parameters on the properties of the micelles was examined. The concentration of PS-b-PEO in the organic phase, temperature, stir rate of the emulsion, organic solvent polarity, and micelle particle loading were all investigated. Particle size only varied when the micelle loading changed. Higher block copolymer concentrations and increased processing temperature increased the rate of the interfacial instability process, forming micelles on the order of minutes rather than hours. This is an important result, because it means the rate of polymer processing and micelle production can be increased significantly above the rates previously reported, and suggests a route to commercial scale-up of these nanomanufactured particles. Utilizing the electrospray-interfacial instability process, we have demonstrated the potential for tunable micelle structures to be produced in a large scale, continuous production process. This technology can be used to create empty and loaded micelles that could have applications in drug delivery, imaging, separations, and diagnostics.