Cluster densities multiplets

At this point, since the distribution of ions between the multiplets and the clusters is known approximately, one can attempt correlations between the various properties which are affected by the presence of ions and the content of the ions in the clusters or multiplets. The most instructive correlations are obtained with the content of ions in the clusters. Fig. 3 shows this relation for the density and the glass transition, while Fig. 4 gives it for the temperature shift obtained from the melt rheology studies discussed before. All three plots are linear, suggesting that it is the clusters that exert the greatest influence on the properties of the ionomers, not the multiplets. 

The mechanical properties of ionomers are generally superior to those of the homopolymer or copolymer from which the ionomer has been synthesized. This is particularly so when the ion content is near to or above the critical value at which the ionic cluster phase becomes dominant over the multiplet-containing matrix phase. The greater strength and stability of such ionomers is a result of efficient ionic-type crosslinking and an enhanced entanglement strand density. 

Note 1 The mobility of the polymer segments surrounding the multiplets is reduced relative to that of bulk material. With increasing ion content, the number density of the ionomer multiplets increases, leading to overlapping of the restricted mobility regions around the multiplets and the formation of clusters. 

A is the average distance between quadruplets in a sample with c = 0.05 and v = volume of onemonomer =50 A3. The attractive interactions cause a coalescence of the multiplets which is limited only by the hard-core repulsion between the monomers. In other terms, the density cannot exceed that of the neutral material. It will be shown that this basic fact leads to a cluster with a well-defined density of charges. It is only at the surface of the cluster that the tension of the chains, through their entropy, plays an important role and limits the size of the cluster. 

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