Additive Manufacturing (AM) provides a new dimension in designing and engineering complex 3D structures. When applied to stimuli-responsive materials, AM might enable an unprecedented control of materials functionality not achievable with conventional materials. Here, we report a facile approach to the fabrication of stimuli-responsive 3D structures via Fused Deposition Modeling (FDM) of an epoxy-based crosslinked polymer. The polymer features a reversible crosslinking network based on Diels-Alder (DA) chemistries, which allows the polymer to melt at elevated temperatures and reform the crosslinking network at a lower temperature. At room temperature, both soft and rigid polymer networks were achieved by varying the length of the prepolymer building blocks and the concentration of the maleimide crosslinker. The Tg the crosslinked polymers can be continuously tuned from -10 oC to 27 oC when the average Mn of the prepolymer was increased from 3,900 g/mol to 4,800 g/mol and the degree of crosslinking was changed from 0.133 to 0.666. First, an epoxy resin was oligomerized into prepolymer building blocks. The Diels-Alder (DA) chemistries, furan and maleimide were introduced into the polymer to construct the reversible crosslinking network, and light-responsive azobenzene dyes were covalently incorporated into the polymer to provide stimuli-responsiveness. During the FDM process, the reversible and dynamic crosslinking bonding between furan and maleimide functional groups can enable fast curing of the polymer resin, while thermal reversibility of the crosslinking network can provide the capability to further amend the printed object shapes. Moreover, light responsiveness of the printed objects can be achieved via the photoisomerization of the covalently attached azobenzene dyes. These results show a promising pathway into future multifunctional adaptable structures that can alter their functionality and shape in response to environmental stimuli.

Adaptive structures via additive manufacturing of stimuli-responsive polymers

2019 Fall National Meeting

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