Internally and Geometrically Structured Functional Polymer Colloids via Flash NanoPrecipitation

Abstract

Polymer colloids with complex morphologies have shown great promise in applications ranging from drug delivery and biosensing to optics and enhanced oil recovery. In order to implement these materials on industrial scales, a processing platform which can generate kilograms of such colloids per day is highly desirable yet remains elusive. We have therefore developed Flash NanoPrecipitation (FNP) as a flexible and economical process to generate structured colloids in a scalable manner. This solvent-exchange process relies on the rapid mixing of a polymer solution with an antisolvent stream to produce supersaturated conditions for polymer chains. Upon exposure to these conditions, the polymer chains collapse and agglomerate to form monodisperse colloids which are electrostatically stabilized. Other mechanisms of stabilization are also explored in this work.

In this dissertation, we have demonstrated the versatility of the FNP platform by exploiting the phase separation of chemically distinct polymers to produce colloids with structural complexity. The morphology of colloids prepared from homopolymer blends is dictated by the interfacial tensions of the various components. We manipulated these interactions through the addition of surfactant molecules and charged functional groups on the polymer chains, creating Janus, core-shell, and non-spherical colloids with precise and independent control over their size and composition. Similarly, the microphase separation of block copolymers was harnessed to create lamellar and micellar colloids with nanometer-scale internal domains.

Hybrid polymer-inorganic colloids were prepared by taking advantage of electrostatic interactions between the polymers and inorganic nanoparticles. Precise control over the placement of the inorganic nanoparticles within the polymer support was achieved by simultaneously tuning the solvent conditions in the system. We also generated colloids with anisotropic surface functionality by using blends of hydrophobic homopolymers and an amphiphilic block copolymer. This resulted in amphiphilic Janus colloids which show promise as Pickering emulsion stabilizers. Using the low-cost, scalable, and flexible process of FNP, we have gained valuable insights into the mechanisms of colloid formation and are now able to predict and produce a wide range of polymer colloid morphologies.