Acoustodynamic Covalent Materials Engineering for the Remote Control of Physical Properties Inside Materials.

Advances in vat-photopolymerization (VP) three-dimensional printing (3DP) technology enable the production of highly precise 3D objects. However, it has been a major challenge to create dynamic functionalities and to manipulate the physical properties of the inherently insoluble and infusible crosslinked material generated from VP-3DP without reproduction. Here, we report the fabrication of light- and high-intensity focused ultrasound (HIFU)-responsive crosslinked polymeric materials linked with hexaarylbiimidazole (HABI) in polymer chains based on VP-3DP. Although the photochemistry of HABI produces triphenylimidazolyl radicals (TPIRs) during the process of VP-3DP, the orthogonality of the photochemistry of HABI and photopolymerization enables the introduction of reversible crosslinks derived from HABIs in the resulting 3D printed objects. While photostimulation cleaves a covalent bond between two imidazoles in HABI to generate TPIRs only near the surface of the 3D printed objects, HIFU triggers cleavage in the interior of materials. In addition, HIFU travels beyond an obstacle to induce a response of HABI-embedded crosslinked polymers, which cannot be attainable with photostimulation. The present system would be beneficial for tuning the physical properties and recycling of various polymeric materials, but it will also open the door for pinpoint modification, healing, and reshaping of materials when coupled to various dynamic covalent materials. This article is protected by copyright. All rights reserved.