Ionic domains dimensions

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). 

The exchange energy coefficient M characterizes the energy associated with the (anti)paraHel coupling of the ionic moments. It is direcdy proportional to the Curie temperature T (70). Experimental values have been derived from domain-width observations (69). Also the temperature dependence has been determined. It appears thatM is rather stable up to about 300°C. Because the Curie temperatures and the unit cell dimensions are rather similar, about the same values forM may be expected for BaM and SrM. 

In microfluidic systems where the EDL is thin compared to the characteristic microfluidic channel dimension, it can be approximated that the net charge density is zero and the ionic concentration is uniform throughout the channel domain. Furthermore, if the Joule heating effect is not concerned, we have /conv 0. diff and CT const. In addition, as discussed earlier the... 

A refinement of the above approach is to treat the composite as a quasihomo-geneous system with specific electronic/ionic conductivities and gas diffusion properties, with the electrochemical reaction distributed uniformly over its volume. The problem has been solved in one dimension by Costamagna et al. [1998], but then-solution appUes to the steady state and is not relevant to the present discussion, which concentrates on the frequency domain. Furthermore, intuition would suggest that a one-dimensional model would not completely describe a system as complex as that depicted in Figure 4.1.14. 

There are many similarities between the membrane pores for Na, and Ca + ions. The pores for Na+ ions are formed from single polypeptide with four identical domains, each domain having six membrane-spanning helices. However, the pores are not identical for all three ions, and although Na ions have a smaller ionic radius than ions, they require a larger pore size because they are more extensively bound to water molecules and the pore has to accommodate the solvating water as well as the Na+ ion. Thus the pore dimensions are quite specific for each ion and probably the stmctures of the LAs are too large to enter the K+ channels. The Na+ channel is known to be less selective than the channel and will... 

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