TECHNICAL FIELD

The present disclosure relates generally to fractal-like polymeric particles having a hierarchical structure of branched fibers, where their thinnest portion extending on the outside can be on the nanoscale. In addition, the present disclosure relates generally to methods of making the particles and uses of the particles.

BACKGROUND

Fractal is a mathematical concept which is directed to self-similarity on multiple scales, and the use of the “fractal” concept has contributed to the development of various functional materials, since fractal-like surfaces have a very large surface area with high roughness and porosity. Fractal-like structured materials may be effectively applicable as thickening agents and superhydrophobic surfaces. For instance, the addition of a small amount of fumed silica, which has a fractal-like structure, can make suspensions notably thick. This is due to the effective phase volume fraction of the fractal silica being much higher than their actual volume, because porous silica clusters occupy a very large volume of space. Additionally, fractal-like structures with low surface energy may be used to fabricate superhydrophobic surfaces.

Microscale fractal-like structures may be formed via “bottom-up” processes, by which small particles or supramolecules are aggregated or assembled into branched structures. For example, fumed silica is assembled by hydrogen bonding among the particles. In addition, molecularly branched dendrimeric polymer molecules are known within the art. However, fractal-like supra-molecular structures driven by a top-down polymer liquid precipitation approach has not been reported. Furthermore, fractal-like polymer particles provided by liquid precipitation, in a “top-approach” may have unique advantages and properties in numerous applications compared to “bottom-up” (e.g., fumed silica) approaches.

SUMMARY

In some aspects, the present disclosure provides particles comprising an aggregate of polymer molecules, and having a branched fibrous structure that includes at least a first portion, a second portion and a third portion, each portion individually having a plurality of fibers wherein the first portion comprises a first plurality of fibers having diameters of from about 10 times to about 100 times larger than the fiber diameters of the third portion, wherein the surface area of the first portion constitutes from about 10% to about 40% of the surface area of the particle; the second portion comprises a second plurality of fibers extending from the first portion having diameters of from about 5 times to about 10 times larger than the fiber diameters of the third portion, wherein the surface area of the second portion constitutes from about 20% to about 50% of the surface area of the particle; and the third portion comprises a third plurality of fibers extending from the second portion having diameters of from about 20 nm to about 500 nm, wherein the surface area of the third portion constitutes from about 10% to about 70% of the surface area of the particle.

In some aspects, the present disclosure provides particles comprising an aggregate of polymer molecules, and having a branched fibrous structure that includes at least a first portion, a second portion and a third portion, each portion individually having a plurality of fibers wherein the first portion comprises a first plurality of fibers having diameters from about 2 μm to about 10 μm, wherein the surface area of the first portion constitutes from about 10% to about 40% of the surface area of the particle; the second portion comprises a second plurality of fibers extending from the first portion and having diameters from about 0.5 μm to about 2 μm, wherein the surface area of the second portion constitutes from about 20% to about 50% of the surface area of the particle; and the third portion comprises a third plurality of fibers extending from the second portion and having diameters less than about 0.5 μm, wherein the surface area of the third portion constitutes from about 10% to about 70% of the surface area of the particle.

In some aspects, the present disclosure provides methods of fabricating the particles. The method comprises: flowing a dispersion medium through a high shear mixer; introducing a precursor solution into the dispersion medium to form a dispersion system comprising the dispersion medium and a plurality of dispersed-phase components of the precursor solution, wherein the precursor solution comprises a polymer dissolved in a polymer solvent at a concentration of from about 3% to about 10% by weight, and the dispersion medium comprises an anti-solvent; and shearing the dispersed-phase components by flowing the dispersion system through the high shear mixer, wherein the dispersion system has a Reynolds number of about 3,000 or higher, whereupon the particle is formed in the dispersion medium.

In some aspects, the present disclosure provides uses of the particles.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

