Phosphonated polysulfones

Scheme 4.7 Different chemical modifications to synthesize phosphonated-polysulfones with mono- di- phosphonic acid goups attached away from the polymer main-chain.

In the frame of work [59],the feasibUity of employing an SnP(V) reaction between Uthiated polysulfones and either dialkylchlorophosphates or diarylchlorophosphates to phosphonate polysulfones without the use of a catalyst was investigated (Scheme 14) ... 

Lafitte, B. and Jannasch, P. 2005. Phosphonation of polysulfones yia lithiation and reaction with chlorophosphonic acid esters. Journal of Polymer Science Part A 43 273-286. 

To prepare new and inexpensive membranes, various trials have been made 196 sulfonated aromatic polyether membrane such as polyether ketones (PEEK),197 sulfonated polysulfone198 and membranes from sulfonated polyphenylene sulfide,199 phosphoric acid-doped polybenzimidazole, (PBI),200 polybenzimidazole having sulfonic acid groups,201 polybenzimidazole with phosphonic acid groups,202 a blend membrane of polybenzimidazole and sulfonated polysulfone,203 sulfonated phosphazene polymer.204... 

The bound ion is usually either an anion such as sulfonate (—SOJ), phosphonate (—POf ) or carboxylate (—CO or a cation such as quaternary (—NR3) or amine (—NH3). But both types can occur together and the polymer is then said to be ampholytic. In each case, the polyion may be strong or weak according to the degree to which it ionizes. For example, polysulfonates and quaternary type polyions are strong, polycarboxylates and amine type polyions are weak, while polyphosphonates are intermediate in nature. 

Phosphonated polymers have been proposed for fuel cells with the expectation of being thermally more stable and better retaining water than sulfonic groups [210, 211]. Phosphonated poly(phenylene oxide) [212], poly(4-phenoxy-benzoyl-l,4-phenylene) [213] and polysulfones [214, 215] have been reported. Phosphonated fluoromonomers were polymerized [164]. Characterization of phosphonated films in terms of their proton conductivity has been reported for some of the phosphonated polymers polyphosphazene [216], trifluoropolysty-rene [217], poly(4-phenoxybenzoyl-l,4-phenylene) [218]. Relatively low conductivity values were reported for most of the polymers prepared up to now. The values for polyphosphazene [216] and for perfluorocarbon polymers [219] were quite encouraging. Phosphonated poly(phenylene oxide) [211] was evaluated in fuel cell-tests. 

Various types of condensation polymers such as aromatic polysulfonates and polysulfides, aromatic polyethers, aliphatic and aromatic polysulfides, and carbon-carbon chain polymers of high molecular weights by the phase-transfer catalyzed polycondensation fi-om combinations of aromatic disulfonyl chlorides, phosphonic dichlorides, activated aromatic dichlorides, and aliphatic dihalides, withbisphenol, aliphatic and aromatic dithiols, and active ethylene compounds. The two-phase polycondensation was generally carried out in a water-immiscible organic solvent-aqueous alkaline solution system at room temperature. The method of polycondensation offers a highly versatile and convenient synthetic method for a variety of condensation polymers. 

The electrophilic phosphonation of polysulfones is achieved by a two-step reaction (i) bromination (ii) phosphonation of bro-minated polymer. Brominated sites located ortho to ether linkage... 

Scheme 4.3 Phosphonation of polysulfones at ortho-to-ether position.

Although the sulfonic acid-based polysulfones show better proton conductivity, they are highly susceptible to hydrolytic desulfonation (i.e. loss of sulfonic acid unit through hydrolysis) at elevated temperatures [39]. Hence, it is required to either find a solution of this critical issue or develop phosphonic acid based... 

Scheme 4.4 Sulfonation and phosphonation of polysulfone in ortho-to-sulfone position.

Lafitte et al. [45] reported polysulfone ionomers functionalized with benzoyl(difluoromethylenephosphonic acid) side chain (bfp-PSU) as an alternative to sulfonic acid based PSU ionomers shown in Scheme 4.8(a) and Table 4.2. The degree of phosphonation (DP) was achieved up to 53% and this membrane took higher amount of water (6%) tmder immersed state at room temperature compared to membrane with phosphonic acid directly attached to main-chain at ortho-to-sulfone position taking 2% water as discussed before. The probable reason is the increased acidity of the phosphonic acid unit. The thermal stability was found to be inferior to sulfonated derivatives due to the presence of aryl -CF2-P linkage [45]. 

Table 4.2 Water uptake, lEC, conductivity and thermal characteristics of different polysulfone ionomers functionalized phosphonic acid.

Recently, phase transfer catalysis has been effectively exploited in the field of synthetic organic chemistry.However, there are scant reports on the syntheses of condensation polymers by phase transfer methods. Five years ago, we started a broad investigation into the use of phase transfer catalysis (PTC) to effect polycondensation. Since then, we have successfully synthesized various types of condensation polymers with high molecular weights. For example, aromatic polysulfonate ni from aromatic disulfonyl chloride I and bisphenol II [Eq.(l)], / aromatic polyphosphonate V from phenyl-phosphonic dichloride IV and II [Eq.(2)], and aromatic polyether VII from activated aromatic dichloride VI and II [Eq.(3)]. ... 

Sulfonation and Phosphonation of Polysulfones and Poly(ether sulfone)s... 

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