Ionic group-dependent structure of complex coacervate hydrogels formed by ABA triblock copolymers

Abstract

This study investigates the nanostructure of complex coacervate core hydrogels (C3Gs) with varying compositions of cationic charged groups (i.e., ammonium and guanidinium) using small-angle X-ray/neutron scattering (SAX/NS). C3Gs were prepared...

Advances, Applications, and Emerging Opportunities in Electrostatic Hydrogels

“…Typical PEC hydrogels comprise a bPE as at least one of the two (or more) oppositely charged components. As such, the simplest way to create a PEC hydrogel is by mixing a triblock polyelectrolyte with an oppositely charged homopolyelectrolyte (Figure a), ,,,, diblock polyelectrolyte (Figure b), , or triblock polyelectrolyte (Figure c). ,,,,,,,,,− , It is also possible to create a PEC hydrogel by mixing a triblock polyelectrolyte with oppositely charged macroions , or multivalent metal ions (Figure d). , Hydrogels with assemblies of oppositely charged bPEs [i.e., diblock, triblock, and pentablock (Figure e)] have also been demonstrated. , Finally, in addition to linear polyelectrolytes, PEC hydrogels have also been created from oppositely charged bPEs possessing nonlinear architectures [e.g., three- and four-arm bPEs (Figure f)]. , It should be noted that these combinations are not an all-encompassing description of PEC hydrogel fabrication pathways; other combinations may exist.…”

“…Variation of the intrinsic parameters affects the network microstructure, including the PEC domain morphology and the distance between domains (i.e., mesh size), which in turn affects the moduli, salt resistance, and other physical properties of the hydrogels. , PEC hydrogels also benefit from another level of tunability provided by the variation of externally controlled parameters. For example, upon the addition of salt (e.g., NaCl), the electrostatic interactions can be screened, thus affecting the moduli and microstructure of the hydrogel. ,,,,,,,, For PEC hydrogels with functional groups that are weakly ionized, pH is another external parameter that can be used to tune their microstructure and properties. , Multiple levels of tunability distinguish PEC hydrogels as a clear choice for precisely designed materials.…”

“…As the bPE concentration increases, the intermicellar distances decrease, resulting in the overlap of their coronae. In the case of ABA triblock polyelectrolytes, a major fraction of the looping B blocks also begin forming bridges between the micelles, resulting in networks with PEC domain netpoints (Figure a, right). ,,,,,,,, …”

“…Self-assembled hydrogels encompass a broad diversity of materials in which polymers are linked together into three-dimensional (3D) networks via noncovalent (and typically reversible) interactions, such as electrostatic interactions, hydrophobic interactions, van der Waals forces, π–π stacking, hydrogen bonding, metal coordination, and host–guest interactions. , The reversible interactions supporting the physical networks enable excellent self-healing and recovery behavior − as well as responsiveness to stimuli in such hydrogels. ,− These features make them highly desirable in biomedical and consumer product applications. , …”

“…These benefits proliferate in hydrogels in which electrostatic interactions drive self-assembly because the long-range electrostatic interactions enable faster self-assembly and greater tunability. , Broadly speaking, electrostatic hydrogels are 3D water-laden polymer networks that are physically connected by reversible ionic interactions. Numerous approaches have been developed for the preparation of electrostatic hydrogels, from simple ionically cross-linked polyelectrolytes to more intricate assemblies of block polyelectrolytes, ,,,,,,,,− macroions, multivalent coordinating ions/metals, and charged surfactants (Figure ). …”