Synthesis and Characterization of Novel Aromatic Polyimides from Aromatic Diamine and 3,3''',4,4'''-p-Quarterphenyltetracarboxylic Dianhydride

Abstract

ABSTRACT:A new rigid tetracarboxylic dianhydride, 3,3"',4,4"' -p-quarterphenyltetracarboxylic dianhydrjde, was synthesized in three steps starting from diethyl 4-bromophthalate. New aromatic polyimides containing a p-quarterphenyl unit were synthesized from this tetracarboxylic dianhydride and various aromatic diamines by the conventional two-step procedure that included ring-opening polyaddition in a polar amide-type solvent and subsequent thermal cyclic dehydration. These polyimides had inherent viscosities of 0.41-0.83 dl g-1, and were insoluble in organic solvents.The glass transition temperatures (Tg) of the polyimides were 220-260°(, and exothermic crystallization was observed on heating above its Tg. Almost all the polyimides underwent melting prior to its decomposition.

Synthesis and Characterization of Novel Aromatic Polyimides from Aromatic Diamine and 3,3''''',4,4'''''-p-Sexiphenyltetracarboxylic Dianhydride

“…This was due to the development of structure ordering by annealing, although we could not detect crystalline order by X-Ray diffraction. This is in contrast to the behavior observed in XV a, 12 where annealed XVa showed an ordered crystalline pattern. The longer p-sexiphenyl unit may cause less movement of polymer backbone and thus less order in chains.…”

“…::, 237-244 °C followed by broad exothermic peaks around 320-420°C above their Tgs, and only polyimide Xlllc exhibited broad endothermic peaks (390-420°C) prior to decomposition. Tg was almost comparable to that of the previously reported polyimides, XV, prepared from 3,3"',-4,4"'-p-quarterphenyltetracarboxylic dianhydride, 12 but crystallization temperatures (Tes) were higher than those of XV. Polyimide Xlllf having the most flexible connecting groups exhibited only Tg at 236°C, and polyimide Xllld with the most rigid symmetric structure did not undergo obvious transition due to crystallinity.…”

“…The IR spectrum (KBr) exhibited absorption bands at 3400-3000 cm -l (OH), and 1700 cm-1 (C=O). 12.91 g (50 mmol) of IV, 200 mL of absolute ethanol, and 0.3 mL of sulfuric acid were added to a flask, and heated at reflux for about 60 h. After the mixture was washed twice with 100 mL 10 wt% sodium carbonate solution, the organic layer was collected, and the aqueous layer was extracted twice with 50 mL dichloromethane. The combined extract was dried over anhydrous magnesium sulfate.…”

“…Recently, we synthesized very rigid polyimides from 3,3"'", 4,4""'-pquarterphenyltetracarboxilic dianhydride and various aromatic diamines. 12 The polyimides were crystallized at about 300°C, which had been hardly observed as almost wholly aromatic polyimides, and had high thermal stability. Therefore, it is of interest to prepare more rigid polyimides and examine the properties of these polymers.…”

“…N-methyl-2-pyrrolidone (NMP) was purified by vacuum distillation over calcium hydride. Diethyl 4-bromophthalate (1), 12 (4-methoxyphenyl)boronic acid (11), 13 and bis(trimethylene)-4,4'-biphenylenediboronate (VII) 14 were prepared as previously reported.…”