Synthesis of colorless polyimides with high T_g and low coefficient of thermal expansion from benzimidazole diamine containing biamide

Abstract

Colorless polyimides (CPIs) with superheat resistance and low coefficient of thermal expansion (CTE) are required urgently to employ as plastic substrates in flexible‐display devices. To attain the target properties, 2‐(2‐methyl‐4‐(4‐aminobenzamido)phenyl)‐5‐(4‐aminobenzamido)‐N‐phenylbenzimidazol (AB‐MPBZ) that contains biamide was synthesized, and its homo‐ and co‐polyimides were prepared with 1,2,4,5‐cyclohexanetetracarboxylic dianhydride (HPMDA) and cyclobutane‐1,2,3,4‐tetracarboxylic dianhydride (CBDA). The crank‐shaft‐like amide groups effectively increases the linearity and stiffness of polymer segments, providing CPI films with low CTE. On the basis, the CBDA based poly(benzimidazole imide) (PBII) series with dense interchain packing exhibits further reduced CTE down to 22 ppm K−1 and increased glass‐transition temperature (Tg) up to 404 °C. Such good thermal properties indicate that the resultant copolyimides have potential applications as colorless flexible substrates. These provide a feasible approach to balance thermal and optical performance of polyimides.

Transparent and highly organosoluble aromatic polyimides with twisted backbone and bulky side substituents for flexible substrate materials

“…In particular, PAPOT‐OPDA presented the highest transmittance at 450 nm (81%) and the lowest cut‐off wavelength (335 nm), while PAPNT‐BPDA exhibited the lowest transmittance at 450 nm (67%) and highest cut‐off wavelength (360 nm). It is worth noting that the transparency of PAPOT‐OPDA exceeds or approaches the recently reported colorless organic polyimides that show T 500 ranged from 80% to 87% and cut‐off wavelength ranged from 305 to 367 nm 48–50 . In contrast to PAPNT‐BPDA, the inclusion of an ether bond in the side group of PAPOT‐OPDA results in a reduction in overall polymer conjugation.…”

“…It is worth noting that the transparency of PAPOT-OPDA exceeds or approaches the recently reported colorless organic polyimides that show T 500 ranged from 80% to 87% and cut-off wavelength ranged from 305 to 367 nm. [48][49][50] In contrast to PAPNT-BPDA, the inclusion of an ether bond in the side group of PAPOT-OPDA results in a reduction in overall polymer conjugation. Moreover, the presence of an ether bond derived from OPDA in the main chain enhances the flexibility of the polymer chains, consequently reducing molecular interactions.…”

Synthesis of colorless polyimides derived from benzimidazole diamines with bis‐amide structures

“…36 So as shown in Table 2, PI1 and PI2 could easily dissolve in commonly used high boiling solvents (NMP, DMAc, DMSO, DMF) without stirring or heating, which was better than our previous copolymer obtained by polymerization with HPMDA but without these side groups in diamines. 32 F I G U R E 4 The 1 H NMR spectrum of poly(benzimidazole imide)s.…”

“…The degree of molecular aggregation had been weakened, which was harmful to the thermal properties 16. So the T g of PI1 and PI2 were lower than our previous work without these side groups 32. To make sure the OLED devices run well, dimensional stability was essential.…”

Synthesis and comparative study of high Tg and colorless polyamide‐imides with different amide‐to‐imide ratio

“…4 Polyamide-imides are usually prepared by three methods; (1) polycondensation of dianhydrides or diamines monomers containing amide group; (2) diacids containing imide group with diamines; (3) copolymerization of dianhydrides and diacyl chlorides with diamines for simultaneous formation of imide and amide groups in polymer chains. [5][6][7][8][9][10] The first two methods involve multistep synthesis of monomers, while the third method is a facile synthesis of PAIs by copolymerization of diacyl chlorides such as terephthaloyl chloride (TPC) with different dianhydrides, and has been recently studied to tailor the excellent properties of PAIs. [11][12][13] For achieving the present target properties, some approaches such as the incorporation of electronwithdrawing bulky trifluoromethyl group (CF 3 ) and alicyclic unit into CPI chains to afford polyimides with high transparency and thermal stability are reported.…”