Highly Fluorinated Poly(arylene ether ketone) Prepared by a CaH₂‐Mediated Polycondensation Reaction

Abstract

Summary: A new reaction procedure has been developed for the polycondensation of hexafluorobisphenol A (6F‐BPA) with bis(pentafluorophenyl) ketone (BPK) in dimethylacetamide (DMAc). In this reaction, CaH2 has been used as a base to facilitate the formation of the phenolate; an alkali metal fluoride was used as a catalyst. Unlike the conventional polycondensation reactions, this procedure avoided producing water during the reaction, and hence, azeotropic distillation with the assistant of a low‐polar co‐solvent is not required. This improvement maintains the high polarity of the reaction medium; consequently, the selectivity of the reaction at the para‐position of BPK is significantly enhanced and polymers with high molecular weights ($\overline M _{\rm n}$ ca. 30 000 Da) can be obtained with very low branching contents (less than 3 mol‐%) and free of any cross‐linked gel particles. In addition to avoiding the formation of water in the reaction, the use of CaH2 also reduced the concentration of the fluoride ion in the solution. These effects minimize chain degradation reactions such as hydrolysis. The use of CaO instead of CaH2 for this reaction produces similar effects. In the case of CaO, traces of water can be introduced into the reaction. The presence of trace amounts of water increases the polycondensation rate, probably due to the enhanced ionization of the phenolate. However, it also causes a hydrolysis of polymer chains, resulting in the elimination of the ketone group in the polymer backbone. Fortunately, this side reaction is highly water and temperature dependent, and can be efficiently prevented by using CaH2 or conducting the reaction at a lower temperature (<65 °C).CaH2‐mediated polycondensation for the preparation of highly fluorinated poly(arylene ether ketone).imageCaH2‐mediated polycondensation for the preparation of highly fluorinated poly(arylene ether ketone).

Partially Fluorinated Arylene Polyethers and Their Ternary Blend Membranes with PBI and H3PO4. Part I. Synthesis and Characterisation of Polymers and Binary Blend Membranes

“…From the experimental results it can be concluded that shorter polymerisation times are preferred because of M w decrease at too high polymerisation times. This M w decrease with reaction time corresponds to a well-known chain scission phenomenon induced by the nucleophilic character of the fluoride ions present in the polymerisation medium [38][39][40][41].…”

Fabrication of Aromatic‐Aliphatic Aminoketone Polymers with Terminal Fluorine Groups

“…Altogether, the disturbing moieties are covalently incorporated in the PAK chains and cycles (see Supporting Information). Therefore we concluded that use of the common base such as K 2 CO 3 , [24,45] , which is established as a suitable catalyst for nucleophilic aromatic substitution of DFB to produce PEK, PES, and related polymers, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] is not suitable to produce molecularly well defined PAK. MALDI TOF measurements of the crude PAK also revealed defects in the polymer chain when solvents such as dimethyl sulfoxide (DMSO), N-cyclohexyl-2-pyrrolidone, and sulfolane, respectively, are used for the syntheses.…”

“…The striking difference of PAK synthesis compared to the syntheses of PEK or PES is due to the fact that K 2 CO 3 base undergoes salt formation with the bisphenol component and carbon dioxide is formed. However, it is also suspected that related imperfections are incorporated in PEK or PES, [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] because NMR spectroscopy is not sensitive enough to prove small amounts of fragments derived from solvent.…”

“…[9] Oligomeric or polymeric building blocks for the target molecules should be readily available via the nucleophilic aromatic substitution reaction [9][10][11][12][13][14][15] of secondary aliphatic diamines with 4,4 0 -difluorobenzophenone (DFB). This simple method would be in analogy to the well-established syntheses of poly(ether ketone)s (PEK) [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] or poly(ether sulfone)s (PES) [34][35][36][37][38] , both based on DFB (Scheme 1). Surprisingly, no reports on the target PAK were available in spite of the fact that related synthetic routes are known, e.g., to produce N-substituted Michler's Ketone derivatives.…”

Synthesis and characterization of fluorinated crosslinkable poly(phthalazinone ether)s bearing tetrafluorostyrene groups for optical waveguides

“…21 The GPC results obtained under these conditions are shown in Figure 1. Note that the specimens used to obtain these data were recovered by dropping the reaction solution into a mixture of acidic water/methanol (2:1 v:v) so that both the polymer and low molecular weight cyclic oligomers were collected.…”