Colorless Polyimides from Fluorinated Ladder Diamines Containing Norbornyl Benzocyclobutene Segments

Abstract

Three fluorinated ladder diamines with norbornyl benzocyclobutene (N2BC) segments were prepared by catalytic norbornene-arene annulation (CANAL) reactions of norbornadiene with fluorinated bromoanilines. NMR results revealed that two regioisomers were obtained for each diamine, with syn-to-anti ratios of ∼2:1. High-temperature solution polycondensation of these diamines with commercial dianhydrides produced a series of colorless polyimides (CPIs). These polymers exhibited extremely high glass-transition temperatures (T g) of 390–479 °C, reasonable coefficients of thermal expansion of 36–61 ppm K–1, and excellent optical transparency (T 400 > 78% and b* < 2.2). These outstanding properties were attributed to the incorporation of fluorinated substituents as well as the rigid but contorted N2BC segments. For certain dianhydrides, the CANAL-F/CF3-derived CPIs exhibited the best optical properties due to their highest fluorine contents, while the CANAL-2F-derived CPIs exhibited the best thermal and mechanical properties, despite the lowest optical transmittance as a result of their most pronounced inter- and intramolecular interactions.

A systematic study of the relationship between the high-frequency dielectric dissipation factor and water adsorption of polyimide films

“…Huang 22 introduced perfluorocyclobutyl aryl ether groups into polyimide with D k (2.37–2.78) and D f (0.0035–0.0071) and guessed that the lower dipole moment density was the main factor in reducing the dielectric loss. However, Wang 23 synthesized low dipole polyimides with fluorinated ladder diamines with low D k (2.59–3.35) and D f (0.004–0.025), indicating that polyimides with low dipoles may also have higher D f . Therefore, it seems that dipoles are not the main cause of high D f .…”

Ultralow Coefficient of Thermal Expansion and a High Colorless Transparent Polyimide Film Realized Through a Reinforced Hydrogen-Bond Network by In Situ Polymerization of Aromatic Polyamide in Colorless Polyimide

“…That is, it should appear in the top right corner of Figure b. Compared with recent reports, the comprehensive performance of CPI-PA 4 obtained in this work is outstanding. ,− ,− The strategy of PA by in situ polymerization in CPI has significant advantages in improving the dimensional stability and thermal properties while maintaining the optical transparency of CPI films …”

Synthesis of Highly Thermostable and Transparent Colorless Polyimides Based on a Semi‐aromatic Tetracarboxylic Anhydride

“…[28] For example, Liu et al [29] reported the PI from 1,2,4,5-cyclohexane-tetracarboxylic dianhydride (CHDA) and triphenylmethylene diamine showed moderate T d5 of 473 °C. The T d5 s of PIs from CpODA and ladder diamines [30] are generally below 480 °C.…”