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Handbook of Size Exclusion Chromatography and Related ...

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y the De Jaeger <strong>and</strong> Mourey groups (30,31). A reason for this is that Z<br />

rubbers show a molecular association in solution caused by their chemical<br />

nature.<br />

It was reported that the SEC <strong>of</strong> Z (polydiphenoxy, polyaryloxy, <strong>and</strong><br />

polyfluoroalkoxy) in pure THF shows an unusually shaped chromatogram,<br />

suggesting adsorption or other nonsize exclusion phenomena (30). The reason<br />

is attributed to the behavior <strong>of</strong> polyelectrolytes arising from the polydichlorophosphazene<br />

residue that is the precursor <strong>of</strong> Z. Also it is responsible<br />

for the formation <strong>of</strong> aggregates in SEC eluants. The addition <strong>of</strong> salts, for<br />

example LiBr (0.1 M), is enough to remove such aggregates. This was also<br />

confirmed by dilute solution viscosity data using an SEC/LALLS system.<br />

Figure 4 shows typical SEC chromatograms <strong>of</strong> polytrifluoroethoxyphosphazene<br />

<strong>and</strong> polydiphenoxyphosphazene obtained by an SEC/LALLS system in THF.<br />

Figure 4 Comparison <strong>of</strong> two polydiphenoxyphosphazene samples <strong>of</strong> very similar RI<br />

chromatogram (lower trace). The LALLS detector seems to reveal some aggregates.<br />

Instrument: Waters Model 150 ALC/GPC. Column: Shodex 80M. Mobile phase: THF<br />

(0.03% antioxidant, 2,6-di-tert-butyl-4-methylphenol). Flow rate: 1mL/min. Temperature:<br />

308C. Detector: RI, LALLS. (From Ref. 30.)<br />

© 2004 by Marcel Dekker, Inc.

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