Robust Catechol Containing Cationic Waterborne Polyurethanes with Antibacterial, UV Protective, and Adhesive Properties

Functional cationic waterborne polyurethanes (CWPUs) with environmental friendliness and excellent mechanical properties are widely desired in the materials industry. However, traditional modification methods such as molecular structure adjustment, crosslinking modification, and physical filling for polyurethane are overly complex and do not typically improve mechanical properties to the point of satisfying the stringent requirements for modern industrial materials. In this study, phenolic acid 3,4-dihydroxybenzoic acid with a catechol structure is applied to neutralize the tertiary ammonium structure on the side chain of polyurethane for the facile preparation of CWPU materials. The effects of this neutralizer on the microstructure, mechanical properties, and functional performance of CWPU samples (e.g., antibacterial, ultraviolet protection, coating properties) are systematically investigated. The results indicate that the catechol structures of the neutralizer provide abundant hydrogen bonding reaction sites, which greatly improves the mechanical properties of the CWPU films with the maximum strength of 43 MPa and simultaneously 1241% elongation at break. Furthermore, catechol structure and cationic attribute endow the CWPUs with excellent adhesion to various substrates, strong ultraviolet protection performance, and antibacterial ability. The proposed approach can be used to prepare robust CWPUs with strong functional performance as highly effective, environmental-friendly materials over a large scale.