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Current and Recent Projects

Multifunctional Polyelectrolyte/Multivalent Counterion Coacervates

The term “complex coacervation” describes associative liquid-liquid phase separation of multi-solute macromolecular mixtures. This phase behavior occurs when the attraction between the complex-forming solute species overcomes their solvent solubility and generates a polymer-rich “coacervate” phase that is in equilibrium with a dilute supernatant phase. The resulting coacervate phases can be tuned to assume a wide array of properties and can be utilized in diverse fields ranging from pharmaceutical, cosmetic and food formulations to underwater adhesion, materials synthesis and catalysis. Recently, we have shown how the mixing of certain types of commercial polyelectrolytes with multivalent counterions can form putty- or gel-like coacervates that can: (1) adhere to a variety of dissimilar substrates while under water; and (2) enable highly sustained release of water-soluble small molecules over multiple-month timescales. Building on these findings, our current work aims to: first, advance understanding of factors that control polyelectrolyte/multivalent counterion coacervate properties; and second, explore the performance of these coacervates in a range of biomedical, household and industrial applications.

Funding:  National Science Foundation (IIP-1701104)

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Directed Assembly of Polyelectrolyte Complex Structures and Devices

Novel applications of stimulus-responsive soft materials (e.g., advanced coatings, biomaterials and soft robotics) require a broad range of well-defined structures. In the case of polyelectrolyte complexes (PECs), the shapes/morphologies typically reflect the spatial arrangement of their self-assembly process. In our older work, for instance, we have shown that morphologies of surfactant/polyelectrolyte microspheres formed via interfacial gelation can be tuned by varying the location where this gelation occurs – i.e., surface gelation leads to the formation of solvent-filled capsules, while homogenous phase inversion results in solid beads. Here, we aim to extend this principle to directing the assembly of custom-shaped PECs, ranging from various anisotropic shapes (such as stars, flowers or toroids), to functional devices such as stimulus-responsive actuators and self-opening, closing or rupturing containers. In doing so, our goals are to: (1) develop innovative strategies to tailoring PEC structure and properties; (2) generate mechanistic guidelines for effectively utilizing these strategies; and (3) examine the performance of the resulting structures and devices in their various potential applications (e.g., controlled release, sensing and regenerative medicine).

Funding:  National Science Foundation (CBET-1150908)

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Mechanistic Design of Polyelectrolyte-Based Pharmaceutical Colloids

Polyelectrolyte micro- and nanoparticles for health-related applications have frequently been prepared through ionotropic gelation of bioderived polyelectrolytes (such as chitosan or alginate). This has been achieved by crosslinking the polymer chains with either multivalent counterions or oppositely charged polymers, and implemented in numerous applications, ranging from drug, gene and food additive delivery, to medical imaging and disinfection. Both the preparation and application of these particles, however, have largely relied on trial and error with little understanding of the molecular and colloidal interactions underlying their properties and performance. To this end, this project aims to: (1) relate the properties of ionically crosslinked polyelectrolyte micro- and nanoparticles to their formation process; and (2) gain a quantitative and mechanistic understanding of the parameters that govern their structure, stability, and payload uptake and release performance.

Funding:  National Science Foundation (CBET-1133795)

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Properties and Applications of Surfactant/Polyelectrolyte Mixtures

Surfactant/polyelectrolyte mixtures are commonplace in household products (e.g., foods, personal care products, cleaning solutions, paints and cosmetics), pharmaceutical formulations, oil recovery and templates for materials synthesis. To advance the use of these mixtures, our work aims to: (1) enhance the fundamental understanding of the molecular, colloidal and macroscopic properties of surfactant/polyelectrolyte complexes; and (2) apply this understanding towards the design of new materials and products. Our most recent work in this area has focused on antibacterial surfactant/microgel mixtures and disposable personal care products.

Funding:  Ohio Development Services Agency (13-0410)

                 U.S. Environmental Protection Agency (SU84014801)

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Contact Information

Phone: 419-530-8254

Fax: 419-530-8086

E-mail: yakov.lapitsky@utoledo.edu