Ionic microphase-separated

However, a very ln ortant question remains unanswered do PE/EMA and PE/EMA-salt blends exhibit one single PE-EMA or PE-EMA-salt phase or do they contain separate PE and EMA or EMA-salt phases In the melt With respect to the melt rheology data, if there are two separate phases in PE/EMA or PE/EMA-salt blends, non-superposibility of both G ai d G" would most likely occur. As previously mentioned, this Is not the case, which suggests that in the melt blends of PE and EMA or PE and EMA-salt form one phase with Ionic microphase separation occuring in blends containing EMA-salt, when the salt concentration is above the critical salt concentration. 

As typically observed in the case of non-ionic block and graft copolymers, the immiscibility of the constituent blocks within the copolymers can induce microphase separation beyond even that which normally occurs due to hydrophobic and hydrophilic sites within statistical copolymer PEMs such as Nation. A relatively recent area of PEM research, ionic block and graft copolymers are interesting from the point of view of providing fundamental understanding about the influence of morphology upon proton conduction... 

The complex with [Li+]/[PO] = 0.10 exhibits a crystalline melting transition followed by a smectic A mesophase. By increasing the salt concentration as in the case of complexes with [Li+]/[PO] = 0.15 0.30, the smectic A phase is suppressed instead, they exhibit a hexagonal columnar mesophase as evidenced by X-ray scattering. The induction of ordered structure in the melt state of the rod—coil molecule by complexation is most probably due to enhanced microphase separation between hydrophobic blocks and polypropylene oxide) block caused by transformation from a dipolar medium to an ionic medium in polypropylene oxide) coil. 

There is a considerable body of experimental and theoretical evidence for two types of ionic aggregates termed multiplets and clusters (95). The multiplets are considered to consist of small numbers of associated contact ion-pairs that are dispersed in the matrix of low dielectric constant, but do not themselves constitute a second phase. The number of ion-pairs in a multiplet is sterically limited by the fact that the salt groups are bound to the polymer chain. On the other hand, clusters are considered to be small microphase separated regions (<5 nm) of aggregated multiplets. Thus, the clusters are rich in ion-pairs, but they also contain an amount of the organic polymer. 

Dynamic Mechanicetl (DM) Analysis. One of the most straightforward methods of investigating the effects of plasticizers on ionomer properties is through measurements of dynamic mechanical properties. Such studies allow observation of how plasticizers influence the Tg of the ionomer as well as the higher temperature transition (hereafter referred to as the ionic transition or Ti) that is associated with the ionic aggregates in microphase-separated ionomers. A number of such studies, as well as DSC or... 

These five sets of observations, plus knowledge of the phenomenon of microphase separation in block copolymers leads to a model of reverse osmosis or ion exchange membranes in which the hydrophobic portions of the polymer chains have come together to form one more or less continuous microphase, while the hydrophilic portions of the polymer chains (ionic groups, -OH groups, -NH2 or > NH groups) have "dissolved" in a small amount of water to form another more or less continuous microphase when the meni>rane is swollen in water. The hydrophilic groups, in most cases, probably form clusters but not continuous microphases in the dried membranes. 

Ionomers are polymers that are functionalized with ionic groups (usually anionic sites) attached at various points along polymeric backbones that are not extensively crosslinked (1-2). Such materials have a tendency to form ionic domains in which the anionic groups and their associated cations are microphase separated from the typically hydrophobic portions of the polymer. Thus, the ionic domains formed are isolated by a medium of low dielectric constant (i.e. the polymeric backbone) although, in some cases, hydrophilic channels have been reported to connect adjacent ionic domains (3). The size and structures of these domains vary with the nature of the cation, the stoichiometry of the polymer, the degree of solvation of the system and the method of preparation. They can be as small as ion-pairscor small multiplets, but in some cases they have been reported to be in the 20-100 A" diameter range. 

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