(621d) Synthesis, Characterization, and Structural Evolution of Designer Block Polyelectrolyte Complexes

Polyelectrolyte complexes, assemblies of oppositely-charged polymers in aqueous solutions, can address broad societal needs as key ingredients in designing multifunctional nanomedicine carriers and gels. However, because of the interconnected roles of chemically-driven interactions and electrostatic associations, the assembly mechanism and kinetics of formation remain poorly understood and variable in terms of reliability. In this work, we employed RAFT polymerization strategies to investigate structure-property relationships in tunable, ionic block polymers. This facilitates opportunities to judiciously vary the ratio of water-soluble neutral to charged block lengths, tailor specific chemical attributes towards stronger or weaker complexation, and functionalize labile ω-chain ends with nucleophilic markers (such as fluorescent dyes) for elucidating self-assembly dynamics. Small libraries of charged systems were prepared in a parallel synthesizer from poly(ethylene oxide) (PEO) methyl ether as RAFT macromolecular chain transfer agents. As an initial model polyelectrolyte platform, we synthesized PEO-b-poly(vinyl benzyl trimethylammonium chloride) (PEO-PVBTMA) and PEO-b-poly(sodium 4-styrenesulfonate) (PEO-PSS) as the positively- and negatively-charged polymers, respectively, modulating structural parameters, molecular architecture, and ionic character between systems. Subsequently, dynamic light scattering, microscopy, and small-angle X-ray scattering were employed to examine ordering into various morphologies as a function of polymer concentration and salt. The rational pairing of well-defined polyelectrolytes ultimately enables pathways of complexation-driven assemblies to be understood, thereby guiding future prediction capabilities and advancing the development of more sophisticated biomaterial properties and applications.