Preparation and characterization of fluorine‐containing aromatic condensation polymers, 5. Aromatic polybenzimidazoles from 4,4′‐(hexafluoroisopropylidene)dibenzoic acid and aromatic tetramine tetrahydrochlorides

Abstract

Two novel fluorine-containing aromatic polybenzimidazoles were synthesized by direct polycondensation of 4,4'-(hexafluoroisopropy1idene)dibenzoic acid with 33-diaminobenzidine tetrahydrochloride and 1,2,4,5-benzenetetramine tetrahydrochloride. The effect of introduction of fluorine on the synthesis and properties of these polymers is discussed. The'new polybenzimidazoles show good solubility in organic solvents, excellent mechanical properties and high thermal stability.

Preparation and characterization of fluorine-containing aromatic condensation polymers. VI. Aromatic polybenzothiazoles from 4,4?-(hexafluoroisopropylidene)dibenzoic acid and tetrafluoroterephthalic acid and 2,5-diamino-1,4-benzenedithiol dihydrochloride

“…Thus, factors that might account for the low molecular weight and low yield are presumed to be Polymer Synthesis the low solubility of Ia in PPA and its thermal sublimation. 17 A greatly improved viscosity of The direct polycondensation of 4,4 -(hexafluoro-1.60 dL/g was successfully achieved by a two-step isopropylidene)dibenzoic acid ( Ia) with 2,5-direaction, first at 140ЊC for 48 h and then further amino-1,4-benzenedithiol dihydrochloride (II) was at 200ЊC for 24 h. The two-step procedure in first attempted in PPMA at 140ЊC for 24 h, ac-PPA also was applied successfully for the synthecording to the conditions optimized for the preparasis of perfluoro-p-phenylene unit-containing PBT tion of perfluoroisopropylidene unit-containing (IIIb) from tetrafluoroterephthalic acid ( Ic) and aromatic polybenzimidazoles (PBIs) from Ia.…”

“…The decomposition temperatures DT 5 and DT 10 , where, respectively, 5% and 10% of the weight were lost, in air were 514 and 527ЊC, respectively. Perfluoro-p-phenylene unit-containing PBT IIIa is almost comparable to those of perfluoroisopropylidene unit-containing aromatic PBI 17 and polybenzoxazoles, 22 but someanisotropy was observed for the concentrated prowhat inferior to that of a typical aromatic PBT detic strong acid and HMPA solutions of perfluororived from terephthalic acid and II.…”

“…The high T g value is almost the same as that of perfluoroisopropylidene unit-containing aromatic PBI. 17 Neither T g nor melting temperature was detectable for crystalline PBT IIIb, however. Perfluoroisopropylidene unit-containing PBT IIIa was stable up to temperatures as high as 470ЊC both in air and nitrogen atmospheres.…”

“…The increased solubility and amorphous nature of PBT IIIa is ascribed to reduced intermolecular forces functioning between the polymer chains due to the introduction of fluorine atom and to looser packing due to the existence of highly distorted diphenylhexafluoroisopropylidene units in the polymer backbone. 16,17 A typical critical concentration curve for rigidrod polymers was observed for perfluoro-p-phenylene unit-containing PBT IIIb in concentrated sulfuric acid and the curve is given in Figure 2. The extremely viscous solutions at concentrations greater than 7 wt % solids showed strong optical The thermal behavior data of the PBTs is listed in Table III.…”

“…characteristics. In the preceding paper, 17 we have Among these polymers, perfluoroisopropyliwater. 4,4-(Hexafluoroisopropylidene)dibenzoyl dene unit-containing PBT IIIa recently has been chloride (Ib) and tetrafluoroterephthaloyl chlosynthesized and characterized.…”