Reactive Extrusion Synthesis of Biobased Isocyanate-Free Hydrophobically Modified Ethoxylated Urethanes with Pendant Groups

Development of hydrophobically modified ethoxylated urethane (HEUR) rheology modifiers enabled the widespread application of waterborne paints and coatings, replacing their environmentally burdening solvent-based predecessors. However, the diisocyanates, required for the conventional synthesis of HEURs, pose severe eco-sustainability threats. In this paper, we demonstrate an innovative approach to avoiding toxic components in the preparation of rheology modifiers by obtaining a new class of water-soluble isocyanate-free hydrophobically modified ethoxylated poly(hydroxy-urethane)s (IFHEURs). The first step in the synthetic pathway was the preparation of CO2-based five-membered poly(ethylene glycol) bis(cyclic carbonate) and its subsequent aminolysis using 4,7,10-trioxa-1,13-tridecanediamine, yielding poly(hydroxy-urethane) (PHU) prepolymers terminated with cyclic carbonate groups. The PHU prepolymers were further extended in a reactive extrusion (REX) synthesis using biobased hydrophobic diamine PRIAMINE 1075. The REX technique made it possible to overcome the typical limitations of the aminolysis reaction and to reach the desired conversion within a moderate reaction time. IFHEURs have been structurally elucidated using FT-IR and NMR spectroscopy techniques, MALDI-ToF mass spectrometry, and SEC analysis and applied as rheology modifiers. The study of their associative behavior in aqueous solutions confirmed that the architectural flexibility of the obtained IFHEURs, containing terminal and pendant hydrophobic groups, opens a perspective for tuneable thickening performance.