Synthesis of colorless polyimides with high Tg from asymmetric twisted benzimidazole diamines

Ultra‐highTgand ultra‐low coefficient of thermal expansion polyimide films based on hydrogen bond interaction

“…The elongation at break of the film is 7.1%–15.9%, thereby showing good flexibility. In addition, its excellent tensile strength (>100 MPa) and tensile modulus (>2 GPa) are enough to meet the application requirements of flexible OLED substrate 13,27 …”

“…1 H and 13 C nuclear magnetic resonance (NMR) spectra were obtained with a Mercury Plus 400 MHz spectrometer and tetramethylsilane as an internal standard. The inherent viscosities (η inh ) of the Polyamic acid (PAA) solutions were measured with an Ubbelohde viscometer at a concentration of 0.5 g dl À1 in DMAc at 30 C. Fourier transform infrared (FTIR) spectra were obtained with a VERTEX 70 spectrometer in the range of 4000-400 cm À1 .…”

“…In addition, its excellent tensile strength (>100 MPa) and tensile modulus (>2 GPa) are enough to meet the application requirements of flexible OLED substrate. 13,27…”

“…Unfortunately, the performance of commercial PI films, such as Kapton H® and Upilex S®, cannot meet the abovementioned requirement for flexible OLED substrates. Therefore, further improvement of T g and reduction of CTE have become hot research topics in the field of PI film materials 13–22 . Previous studies have shown that the intrinsic method, i.e., designing the molecular chain structure of PI, has the most obvious effect on the increase of T g and reduction of CTE 23–25 .…”

“…Therefore, further improvement of T g and reduction of CTE have become hot research topics in the field of PI film materials. [13][14][15][16][17][18][19][20][21][22] Previous studies have shown that the intrinsic method, i.e., designing the molecular chain structure of PI, has the most obvious effect on the increase of T g and reduction of CTE. [23][24][25] Yang et al prepared a series of PI films with pyridine and pyrimidine structures.…”