A Modular Route toward Macromer-Based Dynamic Gels via Prebonded Boronic Ester Cross-Links

Reversible polymer gels are attractive materials as their dynamic cross-links impart properties such as self-healing, stress relaxation, and stimuli-responsiveness. A wide variety of chemistries have been explored to access such networks, among which boronic ester bonds stand out for their biocompatibility, selectivity, and tunable dynamics. Macromer functionalization is a well-established strategy for introducing boronic esters into networks, as the defined architecture of the macromer provides predictable network topologies with a direct link between dynamic cross-link chemistry and bulk properties, traits difficult to design into conventional polymeric materials. However, altering macromer chemistry can be time- and cost-intensive. Here we describe an alternative, modular strategy in which boronic esters are prebonded and coupled to commercial thiol-terminated poly(ethylene glycol) macromers via UV-initiated "click" chemistry. This route enables straightforward network synthesis and characterization, proceeds in high yield under modest UV light intensities, and avoids byproducts that complicate gel mechanics. The modular nature of this approach allows access to macromer-based networks with tunable mechanical and dynamic properties, without the need to synthesize new macromers. The resulting materials display hallmark dynamic mechanical properties and new capabilities, such as spatiotemporal control over macromer-based gel formation, highlighting prebonded cross-linkers as a versatile platform for constructing macromer-based dynamic networks.