Abstract
Catalytic amounts of cesium carbonate are sufficient to initiate the “silyl method”-type step-growth polymerization of phenylene-bis-TMS-ethers and -thioethers with activated aryl fluoride monomers, and can thus be used instead of ce-sium fluoride or potassium carbonate. Cesium fluoride is very hygroscopic and potassium carbonate is generally used in equimolar amounts. The efficiency of catalytic amounts of cesium carbonate is demonstrated by the synthesis of poly(phenylene ether ether ketone) and poly(phenylene sulfide sulfone) examples.
Highlights
The step-growth polymerization reaction of bis-trimethylsilyloxy- or bis-trimethylsilylthio-phenylenes 1 with activated aryl fluorides 2, the so-called “silyl method”, has found wide application in the synthesis of polyphenylene ether ketones and sulfones [1,2,3,4,5,6,7,8,9,10,11,12,13]
That the addition of a small amount of the non-toxic and much less hygroscopic cesium carbonate instead of cesium fluoride is sufficient to initiate the polymerization reaction, resulting in the desired stepgrowth polymerization products
The use of small amounts of cesium carbonate instead of the fluoride or equivalent amounts of potassium carbonate is based on the follow
Summary
The step-growth polymerization reaction of bis-trimethylsilyloxy- or bis-trimethylsilylthio-phenylenes 1 with activated aryl fluorides 2, the so-called “silyl method”, has found wide application in the synthesis of polyphenylene ether (resp. sulfide) ketones and sulfones (see Scheme 1) [1,2,3,4,5,6,7,8,9,10,11,12,13]. The step-growth polymerization reaction of bis-trimethylsilyloxy- or bis-trimethylsilylthio-phenylenes 1 with activated aryl fluorides 2, the so-called “silyl method”, has found wide application in the synthesis of polyphenylene ether Sulfide) ketones and sulfones (see Scheme 1) [1,2,3,4,5,6,7,8,9,10,11,12,13] It involves nucleophilic aromatic substitution reactions on activated aryl halides e.g. 4,4’-difluorobenzophenone or 4,4’-difluorodiphenyl sulfone 2. In the reaction with cesium fluoride, fluorotrim-ethylsilane is formed together with the polymer 3 and regeneration of cesium fluoride from the nucleophilic aromatic substitution step generating a diaryl ether linkage, making a small amount of initial CsF sufficient to promote the step-growth polymerization/polyconden-sation (Scheme 1, method b)
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