Polyaroylation reactions

There is, however, an Important practical difference between the reaction conditions required for successful operation of the routes to polyetherketones as compared with those for the polysulphones and this arises from a crucial difference between the two classes of polymers. Polyethersulphones are amorphous or only slightly crystalline and dissolve readily in polar organic solvents such as nitrobenzene or dimethyl sulphoxide at room temperature, but many polyetherketones develop considerable crystallinity and dissolve only at temperatures close to their melting points in this type of solvent. The insolubility of these polymers presented a major synthetic problan as it limits the molecular weights that could be obtained before the growing chains crystallised out from the polycondensation system and this is the main reason why commercial development of the polyetherketones lagged behind that of the polyethersulphones Solutions to this problem for the polyaroylation reactions, (1), were found first by du Pont and then by Raychem, while for the polyether syntheses the problem was solved by ICl. Raychem manufactured a polymer of structure 1, named Stilan, between 1972 and 1976, and manufacture of the ICI polymer, II, trade name Victrex PEEK", started in 1982. 

The first preparation of completely aromatic polyetherketones was reported by Bonner of du Pont [1], who obtained polymers of low molecular weight (Inherent. Viscosity, IV, 0.13-0.18) by the polyaroylation reactions (3) using both Isophthaloyl and terephthaloyl chlorides as monomers with... 

The main synthetic routes to polyaryletherketones, reactions (1) and (2), are analogous to those used for the corresponding polysulphones, polyaroylations, (1), replacing the polysulphonylatlon processes described in the previous chapter (see p 169), while the halogen atoms displaced in the polyether syntheses, (2), are activated by carbonyl rather than by sulphonyl groups ... 

PEEKS can be made by two general routes. In both cases the main difficulty is to keep the crystallisable polymer in solution. Formation of the carboxyl link by polyaroylation can be carried out in liquid HF by catalysts such as BF3. The reaction is also possible in solvents such as dichlorobenzene with an excess of AICI3 both to catalyse the reaction and to solubilise the polymer by complexing with the carbonyl group in the backbone. AICI3 must then be neutralized and extracted from the polymer. The waste stream contains organic compounds, aluminium salts and hydrochloric acid. 

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