Carboxylic Acid Ionic Modification of Castor-Oil-Based Polyurethanes Bearing Amine Groups: Chemically Tunable Physical Properties and Recyclability

A family of supramolecular side-chain ionic polyurethanes (PUs) is synthesized by a simple method using polyurethanes with tertiary amines as pendant groups, and carboxylic acids. The resulting polyurethanes contain diethyl ammonium and carboxylate moieties that are bonded by a combination of ionic and hydrogen bonds. The self-assembling process is observed by Fourier-transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and nuclear magnetic resonance (NMR) spectroscopy. The synthesized polyurethanes are characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Rheological, dielectric, and mechanical properties are investigated, and it is found that the tunability of the properties depends on the acid functionality and the chain length. Dynamic viscoelastic tests reveal a rapid and complete thermal reversibility, which opens the door to studying the recyclability of the samples.