Hydrophilic monomer-tuned microstructure and performance of CO2-based waterborne polyurethanes

Carbon dioxide (CO 2 ), a renewable C1 feedstock, provides a sustainable alternative to fossil-based polymers. While conventional waterborne polyurethanes are well studied, systematic comparisons of cationic, anionic, and nonionic CO 2 -based WPUs with identical soft segments remain underexplored. Here, CO 2 -based polycarbonate diol (PPCD) was used as the soft segment, and three hydrophilic monomers were introduced to synthesize cationic (C-WPU), anionic (A-WPU), and nonionic (NI-WPU) WPUs. Characterizations revealed distinct performance differences: C-WPU showed a mixing region T g of 6.1°C; A-WPU exhibited a T 5 % of 269°C; NI-WPU achieved superior emulsion uniformity, the highest T 5 % (325°C), and crystallinity (48.2%). This work clarifies the hydrophilic monomer–structure–property relationship and offers a systematic benchmark for low-carbon coating design.