In recent years, there has been massive interest in creating soft materials with customized shapes. Approaches to achieving this have included layer-by-layer deposition, microfluidics, direct-write assembly, various stamping and molding techniques, and photolithography. As part of these efforts, our group has recently shown that custom-shaped polyelectrolyte complexes (PECs) can be prepared using photolithographic directed assembly (where patterned PEC formation is driven by localized photopolymerization of an anionic monomer in the presence of a polycation). Building on this work, here we demonstrate how poly(allylamine)/poly(acrylic acid) PECs prepared by this approach could be used as structure-directing templates for custom-shaped thermoreversible (agarose) gels. This custom-shaped agarose hydrogel formation is achieved by adding agarose to the acrylic acid/poly(allylamine)/photoinitiator precursor solution that is used in the photolithographic directed assembly process (such that the monomer, polymer and photoinitiator are dissolved in agarose gels during the photolithographic PEC formation). Once the custom-shaped PECs form, the agarose gels surrounding the PECs are melted and washed away, whereupon the custom-shaped PECs (which still contain dissolved agarose) are cooled to room temperature again to form an interpenetrating network of ionically bonded PECs and hydrogen bonded agarose gels. The sacrificial PEC templates are then dissolved in concentrated (3.5 M) NaCl solutions, leaving behind agarose gels with shapes and dimensions matching their parent photolithographically generated PECs. This custom-shaped gel preparation strategy can likely be extended to other types of thermoreversible hydrogels and may have applications in fields such as tissue engineering, sensing and bioseparations.

Photopatterned polyelectrolyte complexes as shape-directing templates for thermoreversible biopolymer gels

255th National Meeting (2018)

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