Novel Metal-Containing Polyurethane Elastomers Prepared Using Tetradentate Schiff Base Metal Complexes

A series of divalent metal (Co 2+ , Ni 2+ , Cu 2+ )-incorporated tetradentate Schiff base complexes of the generic name 1,2-bis[(4-(2-hydroxy)ethoxy-2-hydroxyphenyl}methyl ketimino]ethane-metal(II) (BHEHPMKE-M)-metal-containing dihydroxy monomers-were synthesized and characterized by UV-visible, FT-IR, MS, and atomic absorption spectroscopies and elemental analysis. Structure of one of the monomers was also confirmed by single-crystal X-ray diffraction technique. Several metal-containing polyurethanes were prepared using these dihydroxy compounds and 1,4-butanediol as chain extenders for prepolymers based on poly(oxytetramethylene) glycol-2000 (PTMG-2000) and 4,4'-methylene bis(phenyl isocyanate) (MDI). The amount of metal-containing monomer was varied from 0 to 1 equivalent to find the influence of the metal-incorporated tetradentate Schiff base segment on thermal and mechanical properties of polyurethanes. The properties of metal-containing polyurethanes were compared with those prepared using 1,4-butanediol and 1,2-bis[{4-(2-hydroxy)ethoxy phenyl}-methyl ketimino]ethane-a diol without metal-as chain extenders. The polymers were characterized by FT-IR, GPC, DSC, TGA, viscosity, and solubility measurements. The glass transition temperature (T g ) of the polyurethane prepared from the Schiff base diol (without metal) was found to increase when used alone as chain extender. Thermal and mechanical properties of polyurethanes were also found to improve markedly by the introduction of metal-incorporated tetradentate Schiff base moiety into the polymer chain. The viscosity of the metal-containing polyurethane decreased abruptly upon increasing the metal content.