Multifunctional 4D-Printable Boronic Acid-Functionalized Hydrogels for Soft Actuation and Environmental Remediation

This work reports a multifunctional boronic acid-functionalized supramolecular hydrogel platform for potential photocuring-based 4D-printing applications, adaptive soft actuation, and environmental remediation applications. The hydrogel was fabricated through rapid UV-induced photopolymerization by integrating a photoluminescent 4-arm star poly (N, N-dimethyl acrylamide)-block-poly-(4-vinylphenylboronic acid) [4-arm star (PDMA-b-PVPBA)₄-Br] copolymer with acrylic acid (AA), acrylamide (AM), and poly (ethylene glycol) diacrylate (PEGDA). The resulting hydrogels exhibited excellent printability, UV curability, mold-assisted fabrication capability, high structural fidelity, and tenable viscoelastic behavior. Gel_2 exhibiting the optimum balance of rheological properties and mechanical performance. Owing to the synergistic effects of ionizable carboxylic acid groups and dynamic boronic acid interactions, the optimized hydrogel demonstrated pronounced pH-responsive swelling with significantly enhanced swelling under alkaline conditions. Importantly, the hydrogel exhibited thermally induced shape memory behavior governed by its glass transition temperature (T_g ≈ 60°C), enabling programmable blooming deformation and click-grab soft actuator functionality with high shape fixity, excellent recovery efficiency, rapid recovery, and good cyclic stability through reversible supramolecular network rearrangement and thermally activated polymer-chain relaxation. Furthermore, the hydrogel displayed excellent capability toward methylene blue (MB), rhodamine B (RhB), eosin B (EB), Pb²⁺, as confirmed by adsorption kinetics, isotherm analysis, control hydrogels, ICP measurements, and XPS characterization through synergistic electrostatic, coordination, hydrogen-bonding, and supramolecular interactions. This study establishes an effective strategy for designing multifunctional UV-curable supramolecular hydrogels with potential compatibility for future photocuring-based 4D-printing technologies integrated with programmable actuation, adaptive responsiveness, and pollutant sequestration capability for next-generation smart soft-material systems.