Acid‐catalyzed reactions in polyimide synthesis

Abstract

Melts of aromatic carboxylic acids are found to be excellent reaction media for I-pot high molecular weight polyimide synthesis from diamines and tetracarboxylic acid dianhydrides. No reversible reaction of polyamic acids (PAA) formation was observed. The effect of the reactivity equalization was observed for low-and high reactive diamines in acid media.The intrinsic acid catalysis of the imidization reaction was shown to take place also in polycyclization of PAA in concentrated solutions in amic solvents. It is found that the dependence of relative imidization rate (YO conv./ min) vs. AA/N-MP ratio for model low molecular and oligomeric amic acids (AA) in N-MP at 14O-15O0C possesses a sharp maximum near the molar ratio 1 : I , the imidization rate at the point of the maximum being an order of magnitude higher than that for diluted solutions. A scheme is proposed which includes the opportunity of two reaction channels to occur: a usual one (I) and a catalytic one (11). In diluted solutions and in solid phase experiments with easy evacuation of volatile products, the role of catalytic channel I1 is low. To the contrary, in high concentrated solutions or in solid phase experiments under the conditions exluding volatile products evacuation, the catalytic channel becomes the key one. It is proposed that the catalytic reaction proceeds via the common acid catalysis mechanism, the solvent and water playing the role of co-catalysts, probably through the 0 1998 Hiithig & Wepf Verlag, Zug CCC 1022-1360/98/$ 10.00 204 mechanism of ionic dissociation of AA or hydrogen-bound complex AAsolvent. It is shown that the water released in the course of solid phase imidization of phtalamic acid at 140°C under the conditions where vaporization is impossible causes a sharp autocatalytic effect after initial 20%conversion period to obtain entirely imidizied product.

Charge storage performance of polyetherimide Ultem®1000—Influence of secondary antioxidants and purification

“…Also weight loss temperatures in air at 5% ( T 5% ) for 2 and 1a , 534°C and 535°C, respectively, can be considered identical. PEI 3 was synthesized in an one‐step one‐pot synthesis in molten benzoic acid according to a method developed by Kuznetsov6, 8, 9 and purified as described above for 2 . Again η inh , T g , and T 5% were similar to those of 1a .…”

“…PEIs possessing a chemical structure shown in Figure 1 and comparable molecular weight to Ultem®1000 ( 1a, see Table I) were synthesized by two different routes. The polymerization of 2 was carried out in N , N ‐dimethylacetamide (DMAc) according to Liaw et al,7 whereas 3 was prepared via a method described by Kuznetsov,8, 9 which was slightly modified. More detailed procedures can be found in a previous publication 6…”

Synthesis and Structure‐Property Relationships of Fluorinated Poly(ether imide)s as Electret Materials

“…Another quite simple synthetic procedure, especially for diamines of low reactivity, was developed by Kuznetsov (see Scheme ) 17, 24. The reaction is carried out at 150 °C in liquid benzoic acid, which acts not only as solvent but also as catalyst.…”

Synthesis, characterization, and thermal properties of anhydride terminated and allyl terminated oligoimides

“…Indeed, carboxylic acids are found to be excellent reaction media for high molecular weight polyimide synthesis. 21 This synthetic route is achieved in only one step and was used for the synthesis of monoimides. [22][23][24] The method shows several advantages such as the extremely high rate of the cyclodeshydration reaction.…”