Zwitterionic-Cationic, Catechol-Based Polyesters Reinforced by In Situ Sol–Gel Inorganic Nanoparticles for Rebondable Waterborne Adhesion

Unlike conventional solvent-borne systems, which raise concerns regarding volatile organic compound (VOC) emissions and toxicity, the waterborne polymer adhesives developed in this study incorporate marine mussel-inspired catechol functionalities and zwitterionic/cationic moieties into a terephthalate-based polyester backbone. The resulting polymers, PSBD0–PSBD4, exhibit excellent hydrophilicity and rebondable adhesion.

The optimal catechol-bearing formulation, PSBD2, shows a lap-shear strength of 2.09 ± 0.09 MPa, an 83% increase over the catechol-free PSBD0. The polymers are further reinforced by <i>in situ</i> generated Ti- or Si-based sol–gel inorganic nanoparticles. The corresponding PSBD composites achieved average lap-shear strengths of 2.47 ± 0.22 MPa (Ti-based) and 2.72 ± 0.54 MPa (Si-based), corresponding to 18% and 30% increases over neat PSBD2, and the highest single cycle lap-shear strengths reached 3.27 ± 1.18 MPa (Ti-based) and 3.34 ± 0.78 MPa (Si-based) under the best conditions.