Halato-telechelic polymers. XIII. Viscoelastic properties and morphology of low molecular weight polybutadiene bearing alkaline carboxylate end-groups

When end-capped by alkaline carboxylate groups, a low molecular weight polybutadiene ( M ̄n = 4600) behaves as a thermorheologically simple polymer. A secondary relaxation characteristic of the thermal dissociation of the ionic domains is observed in agreement with an Arrhenius-type temperature dependence. Although alkaline carboxylates generally impart a less elastic behaviour to polybutadiene than alkaline earth carboxylates, sodium carboxylate end-groups enjoy a very large degree of association in contrast to all the other alkaline and alkaline earth carboxylates. As a result, sodium carboxylates stabilize a polymer network as efficiently as calcium carboxylates, in spite of the difference in cation valency. The main structural features deduced from dynamic mechanical measurements are supported by the phase morphology as investigated by SAXS. Sodium carboxylates are observed to form the biggest ionic domains with an approximate radius of 12 Å, and to promote light dimensional extension of the chains in agreement with the larger interdomain distances. © 1988.