Improved method for the isolation and purification of water-soluble polyphosphazenes

Abstract

We report in this article an improved procedure to isolate and purify representative water‐soluble polyphosphazenes that dramatically reduces the time and equipment involved, while maintaining or exceeding the yields and purity reported in the literature for these polymers obtained using dialysis methods. This technique takes advantage of the phase transition behavior exhibited by some hydrophilic polymers, namely that associated with the lower critical solubility temperature (LCST). The polymers used in this study were poly[bis‐(2‐(2‐methoxyethoxy)ethoxy)phosphazene], MEEP (1), and two new water‐soluble polymers. These polymers are similar to MEEP, yet they contain a small percentage of a crosslinkable pendant group; either 2‐hydroxyethyl allyl ether (2), or o‐allyl phenol (3). The observed behavior was quite different for these two polymers than that found for MEEP, and is a direct consequence of the pendant group substitution patterns. Although the homopolymer MEEP yielded a single sharp LCST point, the two heteropolymers exhibited this phase transition over a broader temperature range. Further, fractionation of polymer 3, based on pendant group speciation, was possible due to the more hydrophobic nature of the phenol. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1092–1099, 2000

Cross-Linked Polyphosphazene Blends as Robust CO2 Separation Membranes

“…Instead, we utilized the fact that PPZ containing large amounts of MEE will exhibit a lower critical solution temperature (LCST) behavior in water, which is key to this purification method. 27 In this method, the polymer was dissolved in water at room temperature and then slowly heated to approximately 80 °C. Upon heating, the somewhat opaque solution became completely opaque, and the precipitated polymer could be removed by physical means.…”

“…The precipitation in water step was vital to remove inorganic contaminants, but MEEP95-PPZ was too water soluble such that precipitation could not occur at room temperature. Instead, we utilized the fact that PPZ containing large amounts of MEE will exhibit a lower critical solution temperature (LCST) behavior in water, which is key to this purification method . In this method, the polymer was dissolved in water at room temperature and then slowly heated to approximately 80 °C.…”