Highly transparent and organosoluble polyimides derived from 2,2′-disubstituted-4,4′-oxydianilines

Effect of charge transfer and chain stacking on the optical and thermal properties of polyimides derived from sulfone and amide-containing dianhydride

To study the effect of charge transfer and chain stacking on the optical and thermal properties, a group of polyimides (PIs) were prepared from various diamines and dianhydrides containing sulfone, amide, and/or trifluoromethyl groups. Ultraviolet–visible spectroscopy, thermomechanical analysis, and thermogravimetric analysis were employed to study the properties of PIs. PIs containing sulfone and amide groups exhibited transmittance varying from 2.9% to 44.9% at 400 nm with good thermal stabilities of 5% weight loss in nitrogen at 455–466°C. The coefficient of thermal expansion values were 37.7–49.8 ppm/°C and glass transition temperatures were 261–299°C. The improved optical properties are owing to incorporation of amide group that decreases the electron-acceptability and sulfone group that distorts the chains, inhibiting the dense chain stacking. There is a trade-off relationship between the optical property and thermal property.

Preparation and properties of highly organosoluble polyimides derived from 2,2′-disubstituted-4,4′-oxydianilines

Four novel aromatic, symmetrical ether diamines (2,2′-bis(biphenyl)-4,4′-oxydianiline, 2,2′-bis[4′-(3″,4″,5″-trifluorophenyl)phenyl]-4,4′-oxydianiline, 2,2′-bis[4-(naphthalene-1-yl)phenyl]-4,4′-oxydianiline, and 2,2′-bis[4″-(diphenylamino)phenyl]-4,4′-oxydianiline), were successfully synthesized through four steps using p-chloronitrobenzene as a starting material. Highly organosoluble polyimides were obtained by the reaction of these diamines with 2′2 ′-bis[4′-(3″,4″,5″-trifluorophenyl)phenyl]-4,4′,5,5′-biphenyltetracarboxylic dianhydride via a conventional two-step chemical imidization method. All the polyimides were thoroughly characterized by Fourier transform infrared, ultraviolet, fluorescence, gel permeation chromatography, and thermogravimetric analysis. The effect of the fluorine atoms directly linked to the lateral phenyl rings showed excellent dissolution and strong fluorescence. The polyimides exhibited excellent thermal stability, with decomposition temperatures (at 10% weight loss) above 530°C and glass transition temperatures in the range of 258–320°C. These outstanding combined features ensured that these polyimides could be used as memory materials for advanced microelectronic applications.

Palladium-Catalysed and Phosphine-Promoted Synthesis of Diaryl Ethers through Self-Coupling

An efficient, palladium acetate-catalysed, tributylphosphine-promoted direct synthesis of symmetrical diaryl ethers through the self-coupling of aryl fluorides has been developed with K2CO3/ZrO2 as a base. This provides an alternative method to prepare aromatic polymers, important synthetic intermediates and natural products for use in the field of pharmaceuticals and industrial materials.