Solution behavior of α,ω-(dimethylamino)polyisoprene coordinated to transition metal salts

Coordination of the amino end groups of a telechelic polymer to transition-metal salts has been found to modify profoundly the solution behavior of that material. In toluene, the relative viscosity increases rapidly with concentration, in a way that depends on the transition metal. The coordination ability of the metal cations has been observed to be as follows: Ni < Co < Fe < Cu. The sharpness of the increase in viscosity upon increasing polymer concentration can be significantly reduced in a polar solvent and more effectively in a solvent able to compete with the amino end groups for the coordination sites of the transition metal. Moreover, the viscosity effect, and accordingly the association of the amino end groups, appears to be maximum at a Cu/amine molar ratio of 1. Any change in this ratio between 0.33 and 1.25 causes a drop in the solution viscosity. Empirical equations have been derived to fit the experimental hydrodynamic behavior.