Synthesis of polyurethane-ureas containing metal and poly(caprolactone diol) soft segment

Abstract

Hexadentate Schiff base zinc and nickel complexes (MSal2trien, where M = Zn and Ni) have been synthesized and used as chain extender for the synthesis of metal-containing polyureas and polyurethane-ureas. The metal complexes were obtained from metal acetates and ligand, which was prepared from triethylenetetramine and salicyladehyde. These metal complexes were characterized by IR spectroscopy. ZnSal₂trien urea were synthesized in order to investigate the reactivity of the NH groups in ZnSal₂trien towards the isocyanate groups in diisocyanate compounds, including 4, 4'-methylenebis(phenyl isocyanate) (MDI), hexamethylene diisocyanate (WADI) and 2, 4-toluene diisocyanate (TDI). The reaction progress could be observed by the disappearance of NCO absorption in diisocyanate compounds and the appearance of a new C=0 urea linkage. This would give an information, which will lead to the synthesis of polyurethane-ureas. In the synthesis of polyurethane-ureas, prepolymer were first synthesized from the reactions between MD1 and poly(caprolactone diol) (PCL diol) at different molecular weights (530, 1250 and 2000). The prepolymers were then subjected to polymerization with MSal₂trien to yield polyurethane-ureas. Characterizations of polymers were carried out using FTIR spectroscopy, elemental analysis, solubility and viscosity. Their thermal properties were studied by thermogravimetric analysis (TGA). Flammability of polymers was measured by limiting oxygen index (LOI). It was found that the obtained polymers did not show liquid crystalline property. However, the polymers had good thermal stability. From TGA study, the MSal₂trien content and molecular weight of the PCL diol were found to have influence on thermal property of the polymers.