The tough, fluorescent and adhesive elastomer in aqueous dispersion: The contribution of aromatic amide-urea segments

Abstract

The recent researches on waterborne polyurethane (WPU) have been much highlighted to fulfill the both requirements of environment and material performance. Herein, a simple copolymerization approach is demonstrated toward the tough, fluorescent and adhesive WPU elastomer films by the incorporation of para aromatic amide (aramid)-urea segments in the backbone of the polymer. The synthesis of the poly(amide-urea-urethane) was carried out through two steps of chain extension reactions, and the aramid motif, 4,4'-diaminobenzanilide (DABA) was used as the chain extender in the second step of chain extension before the polymer was neutralized and dispersed in water. The aramid-urea segments promoted the H-bonding association of the polyurethane matrix during the film formation of the WPU, which facilitated the microphase separation as well as the pronounced elevation of film performance. Under the DABA content of 4 wt%, the ultimate tensile strength increased to 73 MPa, 380% of that without DABA incorporation. Importantly, the WPU film showed remarkable toughness of 372 MJ·m-3 with the elongation at break of ~1250%. The water adsorption of the film was also suppressed to below 3% in 24 h of the water uptake test. Not only that, but the elastomer film also exhibited high adhesion to metal surfaces to withstand a hanging weight of 27.5 kg with the bonding area of 25 mm × 50 mm. Besides, the film was also able to emit bright blue fluorescence under the excitation of UV light. The combining of high strength, toughness, water resistance and photoluminescence in the WPU will provide the elastomer great potential as environmentally friendly multifunctional material.