CO2-triggered hydrophobic/hydrophilic switchable waterborne polyurethane–acrylate with simultaneously improved water resistance and mechanical properties

Abstract

Traditional waterborne polyurethane (WPU) has poor water resistance because of the incorporation of permanent hydrophilic groups, such as carboxyl group or ammonium salt, into polymer chains. Therefore, developing WPU with excellent water resistance and mechanical properties is highly desirable for industrial applications. In this study, CO2-triggered hydrophobic/hydrophilic switchable waterborne polyurethane–acrylate (WPUA) containing methyl methacrylate (MMA) units were designed and synthesized. The molecular structure, hydrophobic/hydrophilic switchable behavior, water resistance, and mechanical properties were systematically investigated and characterized. The WPUA with 10 wt% MMA exhibited a low water uptake (2.15 wt%) and linear swelling ratio (0.17 L%), as well as a high tensile strength (16.7 MPa) and modulus (85.9 MPa), which were much higher than those of the pristine WPU. This study indicated that the CO2-triggered WPUA dispersed stably as latex particles in water and possessed excellent water resistance and mechanical properties after the film formation.