THIXOTROPIC BEHAVIOR OF METAL-CONTAINING COORDINATION POLYMERS - MELTVISCOSITY OF NEUTRAL ALIPHATIC POLYESTERS WITH ZN CARBOXYLATES

The viscosity behavior of polymer melts containing complexes formed be tween the neutralized polyester poly(diethylene glycol-co-succinic aci d) and Zn acetates is discussed. The melt viscosity of these materials increases with the concentration of metal ions, and shows strong thix otropy and shear thinning. This behavior is attributed to the formatio n of coordination bonds between the electron donor groups within the p olyester chain, and empty coordination sites of the various Zn acetate salts. The coordination complexes were obtained in situ in the polyme r melt, which contains well-dispersed ZnO, by adding an equimolar amou nt of CH3COOH. It is proposed that the shear applied to the polymer me lt destroys the polar network of the coordination polymer at a rate th at is greater than the rate of reformation of the coordination bonds f or the sample returning back to equilibrium, following a shear deforma tion. (C) 1996 John Wiley & Sons, Inc.