3D printable polyelectrolyte complexes with versatile mechanical, responsive, and self-healing properties

Abstract

Additive manufg. has been at the forefront of manufg. in the past decade, due to its ability to overcome geometric limitations inherent with traditional manufg. processes. Photolithog. 3D printing processes, in particular, have been of significant interest due to the resoln. of features that can be achieved using these techniques. However, a large fraction of photolithog.-compatible materials are highly crosslinked brittle polymers, which places an inherent limit on their applications. Recent work in the field have endeavored to address this by making compliant polymers, but these elastomeric photoresins often require high temps. during printing, are highly viscous, or require an involved synthesis. In addn., these compliant polymers typically only have structural purposes and exhibit no other functionality. To incorporate both mech. compliance and stimuli-responsive behavior, we turned to supramol. polymers. Supramol. polymers are classes of polymers that have reversible non-covalent interactions between monomers/polymer chains. These dynamic bonds, such as hydrogen bonding, electrostatic interactions, and etc., allow for a variety of emergent material properties such as self-healing, and shape changing capabilities. In this work, we demonstrate the facile 3D printing of polyelectrolyte complexes (PECs) via projection-microstereolithog. PECs are a class of supramol. polymers that have ionizable functional groups that can form a complex with other oppositely charged compds. We developed a versatile and simple PEC photoresin using in-situ polymn. of acrylic acid in the presence of metal cation crosslinkers. The resulting materials displayed upwards of ~300 % strain and a failure stress of ~4 MPa, as detd. using D638 Std. V tensile testing. 3D printed architectures of this material were shown to exhibit self-healing capabilities and other solvent-dependent behaviors, with properties being easily modified by the choice of metal cation crosslinking species. The versatility and simplicity of this system introduces a large parameter space for 3D printing of self-healable and responsive supramol. polymers with tunable properties.

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