(357a) New Classes of Organic Nanoparticles with Engineered Shape and Functionality: Particles with "Gecko Legs" and Environmentally Benign Antimicrobials

We will discuss the fabrication and applications of new classes of functional (bio)polymer particles, made by scalable processes of antisolvent-induced biphasic precipitation under shear. The process enables the formation of high surface area liquid structures, which can serve as templates for the formation of diverse classes of polymer and biopolymer nanoparticles and nanomaterials. The method was originally used to make dispersions of polymer rods that can act as "superstabilizers" of Pickering foams and emulsions. It also allows scalable manufacture of nanofibers and nanoribbons (Adv. Mater., 27, 2642, 2015). In this talk we will discuss two classes of novel particles made by this technique in our group. Modifications of the shear precipitation technique allowed making new types of sheet-like, ribbon-like and dendrimeric particles. The dendrimeric particles, in particular, constitute a novel type of material with extraordinary structure and properties. These particles are hierarchically structured, with a big branched corona of nanofibers spreading out in all directions. The nanofiber corona around these also called "gecko leg" particles endows them with extraordinary strong adhesion to almost any surface and to each other, and enables unique structure-forming abilities, adhesiveness and rheological characteristics. Secondly, we will present the making and properties of a new class of environmentally-benign nanoparticles with cores made of biodegradable lignin. These particles are fabricated by liquid shear process including water-only pH-jump precipitation. They can serve as highly potent microbicidal substitutes of common silver nanoparticles after being loaded with an optimal amount of silver in the form of adsorbed Ag⁺ ions (Nature Nanotech., 10, 817, 2015). The cationic surface modification of these particles facilitates their adsorption onto bacterial membranes and triggers a targeted release of active Ag⁺ ions. These environmentally-benign nanoparticles illustrate how green chemistry principles can be applied to design sustainable nanomaterials with increased activity and decreased environmental footprint.