Synthesis and characterization of a novel itaconic acid-based internal emulsifier for anionic waterborne polyurethane

A novel bio-based liquefied internal emulsifier is synthesized through the thiol-ene photo-click reaction of itaconic acid (IA) and 1-thioglycerol (TG), with the purpose to replace dimethylol propionic acid (DMPA), an internal emulsifier commonly used in the synthesis of waterborne polyurethane (WPU). Compared to WPU prepared with DMPA, a WPU sample synthesized using the IA-based internal emulsifier (IATG) shows a smaller particle size as well as higher storage modulus, phase separation, and tensile strength. Increasing the IATG content while maintaining the NCO/OH ratio constant increases the specific gravity of the hard segment of WPU, which leads to a significant increase in the 100% modulus of the WPU films. In addition, the content of hydrophilic functional groups increases, resulting in the formation of a stable dispersion with small particle size. IATG is also more environmentally friendly than DMPA when used in the WPU synthesis, because it does not require the use of organic solvents. These results suggest that IATG is an effective environmentally friendly alternative to DMPA.