Waterproof and Reprocessable PVA Vitrimer Films Cross-Linked by Boronic Acid-Functionalized Carbon Dots with Pigment Detection

Water-soluble poly(vinyl alcohol) (PVA) faces challenges in fabricating cross-linking networks with high strength and good reversibility. Herein, a strategy of nanocross-linker was proposed utilizing phenylboronic acid-functionalized carbon dots (B-CDs) to construct high-performance PVA vitrimers. The engineered B-CDs, with precisely controlled nanoscale dimensions (2.4–5.6 nm) and abundant surface functional groups, enabled synergistic chemical cross-linking and physical interactions. The stress relaxation behavior, mechanical properties, water/ultraviolet (UV) resistance, and fluorescent properties, as well as the detection application, were systemically investigated. The results showed that the prepared PVA/B-CDs vitrimer film with a thickness of 90 ± 10 μm exhibited remarkable mechanical strength in water. Compared with pure PVA film, the tensile strength and Young′s modulus of PVA/B-CDs0.5 increased from 63.89 MPa and 1.56 GPa to 130.40 MPa and 2.80 GPa, respectively. After being soaked in water for 5 days, the PVA/B-CDs0.5 films still retained a mechanical strength of one-fourth of the original value. Moreover, the dynamic borate ester bonds in PVA/B-CDs0.5 could endow the PVA/B-CDs composite film with reprocessing ability under hot-pressing. Additionally, the unique fluorescence of B-CDs caused outstanding UV resistance of the PVA/B-CDs film. Furthermore, the PVA/B-CDs film was found to achieve the detection and quantification of three common food dyes as fluorescent probes: tartrazine, sunset yellow, and amaranth.