The Synthesis and Characterization of Some Thermally Stable Polypyrazoles and Acetylene Terminated Aspartimides (1986)

Reactions involving the nucleophilic addition cyclization to activated acetylenes have been employed as a novel route to moderate to high molecular weight polymers. Polypyrazoles (PI to P12) have been prepared from the Michael-type addition cyclization of various aromatic dihydrazines to aromatic dipropynones in m-cresol. The aromatic dihydrazines employed were 4, 4'-dihydrazinodiphenyl ether (4,4' -DHDPE), 4,4 '-dihydrazinodiphenylmethane (4, 4'-DHDPM), and 4, 4' -dihydrazinodiphenyl sulfone (4,4'-DHDPS). The dipropynone sutilized were 1,1’- (1,4-phenylene) bis (3-phenyl- 2-propyn-l-one), (l,4 -PPPO), 1,1’ - (1, 3-phenylene) bis (3 -phenyl- 2 -propyn-l-one), (1,3-PPPO), 1,1 '-(1,4 -phenylene) bis (2 -propyn- l-one), (1,4 -PPO), and 1,1’- (1,3 -phenylene) bis (2 -propyn-l-one), (1,3-PPO). Polymers (PI -P6) obtained from the phenyl substituted dipropynones (1,3 and 1,4 -PPPO's) had inherent viscosities ranging from 0.15 to 0.33 dL/g. The glass transition temperatures (Tg) ranged from 225 to 261°C as measured by differential scanning calorimetry (DSC). The temperatures of 10% weight loss as measured by thermogravimetric analysis (TGA) ranged from 400 to 500°C in air and 470 to 512°C in nitrogen. In a few cases creasable films were obtained by solution casting from chloroform. Polymers (P7-PI2) obtained from the unsubstituted dipropynones (1,3 and 1,4 -PPOs) had inherent viscosities ranging from 0.31 to 1.05 dL/ g. The Tg's ranged from 202 to 266°C as measured by DSC. The temperatures of -10% weight loss as measured by TGA ranged from 415 to 483°C in air and 466 to 512° C in nitrogen. In a few cases creasable films were obtained by solution casting from N, N-dimethylacetamide. Moderate to high molecular weight polypyrazoles were readily prepared by the reaction of aromatic dipropynones with aromatic dihydrazines. In a few cases creasable films were obtained. The Tg's ranged from 202 to 261°C as measured by DSC. The polymers exhibited good thermal stability as measured by TGA. Reactions involving the nucleophilic addition to activated alkenes have been employed as a route to novel acetylene terminated aspartimides (ATA's). Novel ATA's were prepared by the Michael -type addition of a series of aromatic diamines to two moles of N-(3-ethynylphenyl) maleimide (NEM). NEM was prepared by the condensation reaction of 3-ethynylaniline and maleic anhydride. The aromatic amines utilized were aniline,4,4-diaminodiphenyl methane, 4, 4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-bis (3-aminophenoxy) benzophenone, 4,4' -bis (4-aminophenoxyphenyl) sulfone, and 1,1, 3-trimethyl-3, S-bis(4 -aminophenoxy) indane. The ATA's were characterized by infrared spectroscopy (IR) and 1H nuclear magnetic resonance spectroscopy (NMR). The ATAs were isolated as a mixture of stereoisomers since a chiral carbon is created during addition. No attempt was made to separate the stereoisomers. Using a DSC the heats of reaction (ΔH) of the acetylene groups was measured, the ΔH's ranged from -23.2 to -49.2 kcal /mole presumably depending upon acetylene density (concentration).