Expanding the domain of complex coacervate core micelles: formation of mixed micelles and in non-aqueous solvents

Abstract

Nanoparticles formed by electrostatic complexation between opposite charge species have been extensively investigated in recent years due to their different functionalities. Complex coacervate core micelle (C3Ms) is one class of these nanoparticles that has a core-shell structure formed by mixing aqueous solutions of a copolymer with a macromolecule of opposite charges. A diversity of macromolecules can be combined with the copolymer to generate C3Ms with different structural characteristics. And this wide variety of characteristics is one of the reasons why C3Ms are potential systems for different applications such as the incorporation and controlled release of drugs, gene therapy, catalysis, sensors, and synthesis of nanoparticles, as has been demonstrated by recent studies. The process of formation, characterization, and application of C3Ms consisting of copolymer + homopolymer and copolymer + surfactants has been widely reported in the literature. As far as we know,the former are structures in thermodynamic equilibrium while the latter are metastable structures. However, there are still no studies that show the formation of C3Ms constituted by the mixture of the three components (surfactant + homopolymer + copolymer) and how the variation in the proportion between homopolymer and surfactant can cause changes in the structural characteristics and thermodynamic equilibrium of these nanoparticles. In addition, investigations related to the characterization, formation process, and applications of C3Ms have been carried out mostly in aqueous solution so far, even though some of these nanoparticles are efficient for applications that could also be carried out in organic solvents, such as catalysis or sensor application. In this sense, this project proposes the investigation of the structural and equilibrium characteristics of C3Ms made up of copolymer + surfactant + homopolymer, which we will call mixed C3Ms, in different proportions between surfactant and homopolymer. We also propose to investigate the process of formation and characterization of reverse C3Ms made up of copolymer and homopolymer in mixtures of organic solvent and water. The reverse C3Ms will be investigated for the encapsulation of enzyme in polar and nonpolar organic solvent. The structural characteristics of C3Ms will be investigated using light scattering and X-ray techniques (DLS, SLS and SAXS) and microscopy (cryo-TEM) and the process of forming reverse C3Ms in organic solvent will be investigated by Isothermal Titration Calorimetry (ITC). Therefore, this project proposes to expand the studies of C3Ms in areas still little explored and it is relevant both for investigating fundamental issues related to the understanding of the formation and stability of C3Ms in water and in polar and nonpolar organic solvents, and for characterizing C3Ms with great potential for application. Mixed C3Ms containing hydrophobic microdomains in the core can be investigated for encapsulating hydrophobic molecules, whereas C3Ms in organic solvents can be potential systems for encapsulating enzymes and promoting catalysis in non-aqueous media. (AU)