Encapsulation of Inorganic Nanoparticles by Anionic Emulsion Polymerization of Diethyl Methylene Malonate for Developing Hybrid Microparticles with Tailorable Composition

Abstract

Colloidal particle self-assembly into higher-ordered structures has been of great interest due to the promise of creating metamaterials with novel macroscopic properties. The physicochemical properties of these metamaterials can be tailored to achieve composites with tunable functionalities, either by controlling the assembly morphology and/or chemistry of the colloidal building blocks. This work describes a strategy of developing microparticles with a hybrid configuration that have an inorganic and an organic part. The inorganic part comprises functional nanoparticles, which are embedded within an organic polymer particle composed of diethyl methylene malonate polymer [p(DEMM)] prepared using anionic emulsion polymerization. DEMM polymerization is initiated entirely by the presence of hydroxyl anions and the resulting particle diameter can be tuned between 300 nm and 1 micrometer by reaction pH. Inorganic nanoparticles with varying chemistry (TiO2, CdTe, ZnO) can be loaded into the p(DEMM) particle with a controlled weight fraction, as confirmed by thermogravimetric analysis. The colloidal stability of the composite microparticles is seen to be dependent on the ligand coating attached to the inorganic constituent. These results provide a synthetic groundwork for creating hybrid, stimuli-responsive microparticles.

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“…Microstructures range from 1 to 1000 μm, and they can be manufactured from synthetic, semi-synthetic, and natural components through physicochemical routes, such as solvent evaporation, spray-drying, and anionic polymerization methods, respectively [ 118 , 119 , 120 ]. As represented in Figure 5 C, microparticles are convenient as they can be manipulated to formulate solid, semi-solid, and liquid products that can be administered orally, intravenously, intramuscularly, or subcutaneously to successfully deliver and enhance the efficacy and bioavailability of one or more drugs [ 121 ].…”