Sheng Lung Chang

Electron-withdrawing/donating effects of substituents on the preparation of phosphinated 4,4 '-diaminodiphenylmethane for soluble, anti-oxidative, and high-Tg polyimides

In this work, we reveal a strategy to prepare a phosphinated 4,4′-diaminodiphenylmethane, 1,1-bis(4-aminophenyl)-1-(6-oxido-6H-dibenz oxaphosphorin-6-yl)methane (3). During the preparation, it was found that the effect of the electron withdrawing/donating characteristic of substituents is crucial to the synthesis. A reaction mechanism including nucleophilic addition, reduction, and electrophilic substitution is proposed. Based on diamine (3), a series of polyimides (4a–4d) were prepared. Polyimides 4 are readily soluble in some organic solvents, and can be solution cast into flexible and foldable films. They show high T g (310–390°C), high moduli (3.34–4.63 GPa), moderate coefficient of thermal expansion (46–58 ppm °C−1), good anti-oxidative stability (T d 5%: 480–537°C (N2); 456–504°C (air)), and good flame retardancy (VTM V-0 rating).

Effect of orientation of phosphinate pendant on the transparency of polyimides: Design and synthesis of phosphinated diamines with a bulky ortho substitution for high-Tg, transparent polyimides

Aromatic polyimides (PIs) are well-known as high performance material because of their excellent thermal and mechanical properties. They are widely applied in electronics and aerospace industries. Despite their outstanding properties, most PIs are typically yellow to amber in color because of the conjugation of the polymer chain and the formation of intermolecular/intramolecular charge transfer complex (CTC). This feature limits their application in optics such as flexible solar radiation protectors and orientation films in liquid crystal display devices. Studies have reported that the incorporation of bulky pendants can reduce the CTC effect.1–9