Preparation and Properties of Thermally Stable Polyureas Containing Ether and Ketone Units

The main objective of this search was to prepare novel soluble polyureas with improved thermal stability. Accordingly, a new types of polyureas was prepared through the polycondensation reaction of a prepared diamine containing ether, keto, and naphthyl groups with 4,4’-diphenylmethan diisocyanate (MDI), toluene-2,4-diisocyanate (TDI), and isophorone diisocyanate (IPDI) in N-methyl-2-pyrrolidone (NMP). Conventional spectroscopic methods and elemental analysis were used to characterize the structure of the monomer and polymers. The results showed that polyurea samples with the expected structure were synthesized. The inherent viscosity of polymers at a concentration of 0.5 g/dL in NMP at 30 °C was in the range of 0.55-0.60 dL/g. Thermal properties of resultant polyureas were investigated by differential scanning calorimetry and thermogravimetric analysis, and they indicated improved thermal stabilities in comparison with common polyureas. Physical properties of the polymers were also studied; they were soluble in common dipolar aprotic solvents. MDI-based polyurea showed highest thermal stability and lowest solubility among the prepared polymers.