Thermal Behavior of Fluorinated Aromatic Polyethers and Poly(ether ketone)s

Abstract

Eight amorphous polyethers and poly(ether ketones) were synthesized and characterized by gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical thermal analysis. Polymers containing bulky, cyclic 2,2‘-biphenyl side groups were found to have the highest glass transition temperatures, were more thermally stable and exhibited the highest intramolecular barriers to rotation. Incorporation of perfluorophenylene groups resulted in internal plasticisation and a relative lowering of T g. The steepness of cooperativity plots determined from Williams−Landel−Ferry shift factors correlated with the rigid nature of the polymer chains, but not with the broadness of the relaxation (characterized by the Kohlrausch−Williams−Watts stretch exponent β) as predicted by the coupling model. A β-process observed in the polymers containing cyclic biphenyl side groups was similar in appearance to a typical “structural” relaxation. The position, intensity, and breadth of the γ-process was sensitive to chemical structure and absorbed moisture.

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

“…Anhydrous dimethyl acetamide (DMAc), KF, CsF, CaH 2 , Ca(OH) 2 and CaO were purchased from Sigma-Aldrich Ltd. and used as received. Two other types of CaO samples were also used.…”

“…Fluorinated poly(arylene ether ketone)s (FPAEK) [1][2][3][4][5] are conventionally prepared by the polycondensation of the phenol groups of hexafluorobisphenol A (6F-BPA) with para-fluorines of bis(pentafluorophenyl) ketone (BPK) using a nucleophilic aromatic substitution reaction (S N Ar), [6][7][8][9][10] which has been traditionally used for the preparation of nonfluorinated poly(arylene ether)s. [11,12] The major problem of this reaction when applied to the preparation of FPAEK is the high tendency of a side reaction at the ortho-fluorines of BPK, [3,4] which are activated by the strong electronwithdrawing effect of the ketone group. [10] This side reaction leads to the formation of branched and eventually crosslinked structures.…”

“…Initial work in our laboratory has shown that this side reaction produces a certain amount of branched and cross-linked structures in the final product when the conventional reaction conditions were used. [4][5][6][7][8][9] Even under mild reaction conditions (i.e., at 113 8C) when molecular sieves were used to dehydrate the solution, a shoulder peak associated with branched structures was observed in the GPC curves of the final products. [3,13] In addition, it was also noted that molecular weights obtained were always lower than the designed values due to this side reaction upsetting the Summary: A new reaction procedure has been developed for the polycondensation of hexafluorobisphenol A (6F-BPA) with bis(pentafluorophenyl) ketone (BPK) in dimethylacetamide (DMAc).…”

“…[14,15] The use of a highly polar solvent induces a higher polarity to BPK and, thereby, selectively promotes the reactivity of the para-fluorines. However, under these conventional reaction conditions with the use of K 2 CO 3 , [5][6][7] water is produced during the reaction and has to be removed due to the potential hydrolysis of the polymer. [16] Therefore, a low boiling, non-polar co-solvent such as toluene has been introduced into the reaction medium to facilitate the removal of water by azeotropic distillation [5][6][7] or by refluxing.…”

“…However, under these conventional reaction conditions with the use of K 2 CO 3 , [5][6][7] water is produced during the reaction and has to be removed due to the potential hydrolysis of the polymer. [16] Therefore, a low boiling, non-polar co-solvent such as toluene has been introduced into the reaction medium to facilitate the removal of water by azeotropic distillation [5][6][7] or by refluxing. [3,13] Unfortunately, this approach reduces the polarity of the polymerization medium and results in a lower selectivity of the reaction.…”