Encapsulation
ENCAPSULATING AGGRESSIVE REACTANTS
Micro and nanoscale polymeric capsules are vital for an impressive array of applications. Whether as transporters, storage containers, or responsive vehicles, these structures impact drug delivery, energy storage, and sensor applications. Further, they are vital for the cosmetic, food, paint, construction, and oil industries. Different applications require different capsules, characterized by distinct geometrical, mechanical, and compositional combinations, and thus inspire work by our lab to provide solutions to the outstanding problems in the field.
Particularly challenging is encapsulation of strongly reactive chemicals like mineral acids, blowing agents, and reducing agents, for example NaBH4 or TiCl3. Even more challenging is encapsulation of these aggressive chemicals on nanometer length scales. Subsequently, our work addresses the fundamental synthetic challenge of encapsulating sensitive, volatile, and reactive compounds within polymeric shells, and thus imparting function to micro- and nano-sized structures. Varying encapsulated payloads and tailoring specific shell properties, we produce multifunctional capsules for self-healing materials, acoustic/radiogenic imaging technologies, for example CT, MRI, X-ray, targeted drug delivery, hydrogen storage technologies, and nano-containment of hygroscopic chemicals for industrial application.
Some examples of our work include:
Thermally-Expandable Microcapsules
- One-pot synthesis of thermally-expandable single-core microcapsules with multiple blowing agents and in nearly quantitative yield.
- Miscible or immiscible blowing agents directly determine, according to either Raoult’s or Dalton’s law, vapor pressure inside the capsules and expansion temperature.
Wrinkled Microcapsules for Controlled Release
- Tuning core vapor pressure and crosslinked shell modulus leads to wrinkled shell morphologies.
- Capsule morphologies were varied from highly-corrugated to nearly-spherical surfaces.
Microcapsules for Acid Encapsulation
- Through single and double emulsion techniques, we encapsulated oil-soluble solid compounds and even aqueous compounds, such as mineral acids.
Monodisperse Nanocapsules
- A series of hollow nanoparticles with accurately-controlled size and shell thickness
- The particles can selectively encapsulate a variety of payloads, such as ionic salts.
Submicrometer Encapsulation of NaBH4
We present a single-step, grafting-to synthetic method for the encapsulation of particulate NaBH4 by dopamine end-functionalized polymer chains. Metal-catechol coordination chemistry is used to produce core-shell capsules, which generate H2 gas exclusively upon adsorption to an oil-water interface.
Significantly, the synthetic process enables facile control of core diameter, shell thickness, and the chemistry of both shell and core. The interfacial reactivity of these stimuli-responsive capsules may be engineered for various applications such as medical diagnostics, therapeutics, and subsurface imaging. In addition to their triggered reactivity, the capsules react in a manner independent of pressure, and are thus well-suited for high pressure subsurface environments.