DYNAMIC MECHANICAL RELAXATIONS OF ETHYLENE IONOMERS

Dynamic mechanical properties were measured for metal salts (Li, Mg, Na, and Zn) of poly-(ethylene-co-methacrylic acid) (EMAA) using a dynamic viscoelastometer. The study reproduced the previous observation that the mechanical relaxation behavior clearly responded to ionic cluster formation and its phase separation from the hydrocarbon matrix-the Li, Mg, and Na ionomers formed ionic clusters at a neutralization of approximately 35% or higher, and the Zn ionomer did not form ionic clusters at neutralization up to 60%. However, this work has revealed clear evidence that even the Zn ionomer forme regions of microphase-separated ionic clusters at a neutralization of 80% or higher. A peak, designated as the a' peak, appeared at approximately 325 K on the loss modulus curve of all EMAA ionomers that form ionic clusters, and the temperature exhibiting this peak proved to be independent of frequency. The order-disorder transition temperature (T(i)) of the ionic clusters of EMAA ionomers, measured by differential scanning calorimetry, agreed with the alpha' peak temperature. From the frequency independence of this alpha' peak temperature, it is proposed that the alpha' peak is regarded as a first-order transition at T(i) and represents the existence of the order-disorder transition in the ionic clusters.