Ionic domains

Zinc salt of maleated EPDM rubber in the presence of stearic acid and zinc stearate behaves as a thermoplastic elastomer, which can be reinforced by the incorporation of precipitated silica filler. It is believed that besides the dispersive type of forces operative in the interaction between the backbone chains and the filler particles, the ionic domains in the polymer interact strongly with the polar sites on the filler surface through formation of hydrogen bonded structures. 

With increasing water content, the ionic domains swell from 40 to 50 A in diameter and the structure of fhe membrane is fhoughf to consist of spherical ionic domains joined by cylinders of wafer dispersed in fhe polymer matrix. Within this region of wafer confenf, proton conductivify steadily increases. At > 0.5, a morphological inversion occurs in which a connected network of aggregated polymer "rods" is now surrounded by water. This network continues to swell for X, = 0.5 —> 0.9 and fhe conductivify of fhe membrane approaches the values observed for Nafion solutions. 

Further evidence for microphase separahon has been seen by AFM. As expected, BPSH 00, with no ionic regions, displays no significant features in its AFM image. For BPSH 20, isolated ionic clusters have dimensions of 10-25 nm. These clusters are even more readily discerned from the non-ionic matrix in BPSH 40, but the domains appear to remain relatively segregated from each other. In the case of BPSH 50 and 60, connections between domains are clearly visible, especially in the case of the latter sample. It also should be noted, however, that these samples were in a dehydrated state. Therefore, it might be expected that even in the case of the lower acid content samples, it is likely that some channel formation between ionic domains will still occur upon the uptake of water. This can be clearly seen in its linear conductivity behavior as a function of disulfonated monomer (i.e., the percolation threshold has been reached by at least 20-30% content of disulfonated monomer). 

McLean, R. S., Doyle, M. and Sauer, B. B. 2000. High-resolution imaging of ionic domains and crystal morphology in ionomers using AFM techniques. 

Using contrast matching methods of SANS, Nafion was swollen with various mixtures of H2O and D2O in order to highlight the scattering features of the water swollen ionic domains. Furthermore, quenched samples were used in these studies to eliminate the scattering features attributed to the crystalline do-... 

Figure 3. 2-D SAXS scattering patterns of (a) as-received Nafion, showing a slight morphological anisotropy in the ionic domains from the membrane calendaring process, and (b) uniaxially oriented Nafion (Ab = 5.4).

Figure 7. Conceptual model for the morphological reorganization and continuity of the ionic domains in Nafion as the dry membrane is swollen with water to the state of complete dissolution. (Reprinted with permission from ref 76. Copyright 2000 Elsevier.)...

Note 2 Ionic groups are usually present in sufficient amounts (typically less than 10 % of constitutional units) to cause micro-phase separation of ionic domains Ifom the continuous polymer phase. The ionic domains act as physical crosslinks. 

The ionic domain around the complex affects the rate of photochemical reaction by attracting or repulsing the substrate. The polymer pendant Ru(bpy)2+ was prepared from a poly(Vbpy-co-acrylic acid) (9 Ru[P(Vbpy-AA)] (bpy)2+)33). 

The ionic domain of polyelectrolytes also affects the photoinduced charge separation between the coexisting low molecular charged compounds38). The quenching of Ru(bpy)2 + by a zwitterion compound, dibenzylsulphonates viologen (18, BSV), was enhanced about 4 times by poly(vinylsulphate) (PVS)39), and the back reaction... 

The Rh, Ru, and Pt ionomers of perfluoro- carbonsulfonic acid polymers have been formed and reduced to investigate the formation of metal particles within the ionic domains of these materials 88). The particle size distributions peak in the 2.5 to 4.0 nm range. The reduced ionomers catalyze the CO oxidation with the activity sequence Ru > Rh > Pt. Diffusion limitations occur in the cases of the Rh and Ru, but not the Pt, ionomer catalysts. 

Transferability of ionic domains The Lewis S4)-Sidgwick-Powell 66)-Gillespie-Nyholm S6> rule... 

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