Synthesis and properties of waterborne polyurethane incorporated with phenolic acid grafted oligochitosan

Phenolic acid grafed oligochitosan (PA-g-OCS and GA-g-OCS) have been synthesized through the reaction of protocatechuic acid and gallic acid with oligochitosan, which was catalyzed by laccase. Subsequently, the two modified waterborne polyurethanes (POCS-WPU and GOCS-WPU) were obtained using PA-g-OCS and GA-g-OCS as biobased crossing agents to react with polyurethane prepolymer, respectively. The structure of POCS-WPU and GOCS-WPU was characterized by Fourier transform infrared (FTIR) and Ultraviolet-Visible absorption (UV–vis) spectroscopy, and the properties of POCS-WPU and GOCS-WPU coatings were examined. The results elaborated that both of the films present fine water contact angle, pronounced mechanical properties (tensile strength, 23.26 and 29.39 MPa; elongation at break, 504 and 491%, respectively) and significant thermal stability. Moreover, the polymers exhibited favorable antioxidant activity measured from the DPPH and ABTS radical scavenging assays.