A Novel Strategy to Polyurethanes with Improved Mechanical Properties by Photoactivation of Amidocoumarin Moieties

Polyurethane (TPU) is a multifunctional material, which has a wide range of commercial applications in anticorrosive coatings, vehicles, railways, aircraft, cargo ships and other fields. In addition, other important applications for TPU are adhesives, sealants or elastomers, as these polymer systems combine excellent and attractive physicochemical properties at a competitive price. However, for some applications, such as protective coatings for body weathering, excellent mechanical properties including toughness, tensile strength, and even Young's modulus are urgently required. Therefore, improving the mechanical properties of polyurethane coatings is an important research topic.

In this work, the preparation of polyurethanes by inserting a small number of coumarin units is a good strategy to promote the general mechanical properties of polyurethanes by dimerizing these photoreactive units. A novel amido-coumarin diol, which is easy to introduce into polyurethane hard segments, was synthesized. A small fraction of this compound (5% by weight) is enough to significantly trigger the mechanical properties of these materials, namely chemical crosslinking via ultraviolet light. Especially when the additive is present in the hard segment, the improvement caused by the dimerization is more important to the mechanical properties of the coating, although the dimerization process is more hindered. The formation of coumarin dimers is the main molecular mechanism of simultaneous hardening, strengthening and toughness. Because the hard domain is used in polyurethane, increasing the stiffness of these segments produces better strengthening and strengthening effects. This study provides an effective method for improving the mechanical properties of polyurethane.

DOI:10.1039/d0ra06372j