Swollen polymer clusters

Using the same sample (e = 2 x 10" ) fractionated and then diluted in TDF (BC < 1), we were able to measure the fractal dimension (see Rel. I4b) of the swollen polymer cluster because all the polymers are larger than the scale length q at which the polymers are observed ... 

Diffusion of cations in a Nation membrane can formally be treated as in other polymers swollen with an electrolyte solution (Eq. (2.6.21). Particularly illustrative here is the percolation theory, since the conductive sites can easily be identified with the electrolyte clusters, dispersed in the non-conductive environment of hydrophobic fluorocarbon chains (cf. Eq. (2.6.20)). The experimental diffusion coefficients of cations in a Nation membrane are typically 2-4 orders of magnitude lower than in aqueous solution. 

Nafion is a novel and unique family of polymers which consist of a perfluorinated backbone and short pendant chains terminated by sulfonic groups. When swollen in water, the structure of Nafion is believed to resemble that of an inverse micelle (Fig. 3) [16-18], The hydrated SOf head groups are clustered together in a... 

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. 

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