Synthesis of Superheat-Resistant Polyimides with High T_g and Low Coefficient of Thermal Expansion by Introduction of Strong Intermolecular Interaction

Abstract

The development of polyimides (PIs) with a superheat resistance and a high thermal dimensional stability is required urgently for application in the rapidly growing area of flexible-display substrates. Based on an enhanced intermolecular interaction, 2,2′-p-phenylenebis­(5-amino­benzimidazole) (DP) that contains bis-benzimidazole was synthesized, and two series of its copolyimides (PI-a and PI-b) were prepared by copolycondensation with 5-amino-2-(4-aminobenzene)­benzimidazole (PABZ) and 5-amino-2-(3-aminobenzene)­benzimidazole (i-PABZ), respectively. The high density and packing coefficient of the resulting PIs caused by the strong intermolecular interaction from the hydrogen bonds and the charge-transfer complex provided the PI films with a very high glass-transition temperature (T g > 450 °C) and an extremely low coefficient of thermal expansion (CTE) below 10 ppm/K for PI-a. Such good thermal properties expand their application as high thermostable materials. Furthermore, the PI-b had a higher T g than PI-a, whereas the latter had lower CTE values because of the configuration difference of their polymer chains. These data indicate that the resultant thermostable copolyimides have potential application as a flexible-display substrate and provide a feasible method to improve the thermal properties by incorporating bis-benzimidazole moieties.

Synthesis of polyimides with lower H2O‐absorption and higher thermal properties by incorporation of intramolecular H‐bonding

“…It was well established that the PBIIs possessed strong intermolecular hydrogen bonding interactions with strong proton donors (NH) and proton acceptors (CO) and this intermolecular interaction was able to be certificated in the FTIR spectra of polymers . In general, with an increase in BI‐containing content of the copolyimides, the band positions of CO gradually shifted toward lower wave numbers.…”

“…It was well established that the PBIIs possessed strong intermolecular hydrogen bonding interactions with strong proton donors ( NH ) and proton acceptors ( C O ) and this intermolecular interaction was able to be certificated in the FTIR spectra of polymers. [7,14,21] In general, with an increase in BI-containing content of the copolyimides, the band positions of C O gradually shifted toward lower wave numbers. However, for the copolyimide-PyPABZ series, the shift of imide carbonyl asymmetric stretching was 1,776 cm −1 and that of the symmetric stretching was 1,725 cm −1 without redshifts as the content of the BI moiety increased (Figure 2).…”

“…[7][8][9][10] The high performance are exactly confirmed to be due to the chain-chain hydrogen bonds originated from strong proton donor and proton acceptor, [11][12][13] but the ability to form intermolecular H-bonding of BI ring enhances the possibility of hydrogen-bonded water molecules formation and, thus, increases the water retention of corresponding materials. [12,14,15] The high H 2 O-absorption in PI fabrications may cause degradation of dielectric properties, dimensional changes, and delamination to restrict the commercial application of materials. [12] It is well known that intramolecular hydrogen bonding interactions hinder the H-bonding formation between substrates and water, along with improve the rigidity and nonrotatory of molecules.…”

Preparation and Properties of Inherently Black Polyimide Films with Extremely Low Coefficients of Thermal Expansion and Potential Applications for Black Flexible Copper Clad Laminates

“…At last, the dimensional stability of the PI films at elevated temperatures were investigated by the TMA measurements and the CTE values of the PI films in the temperature range of 50-250 °C were recorded, as shown in Figure 10 and Table 2. Benzimidazole units have been widely incorporated into the molecular structures of PI films either for decreasing the CTE values of the films [31,32], increasing the modulus of the films [33], increasing the Tg values of the films [34], or increasing the bonding strength with the copper foil [35] due to the strong intermolecular interactions resulting from the formation of the hydrogen bonding for the benzimidazole-containing PI films [36]. At last, the dimensional stability of the PI films at elevated temperatures were investigated by the TMA measurements and the CTE values of the PI films in the temperature range of 50-250 • C were recorded, as shown in Figure 10 and Table 2.…”

Alkaline‐developable and negative‐type photosensitive polyimide with high sensitivity and excellent mechanical properties using photo‐base generator

“…Therefore, next-generation PSPIs for the electronic packaging should meet several requirements including: (a) High thermal stability and low coefficient of thermal expansion (CTE) to prevent curling, cracking and detaching of the PI films from silicon wafers during exposing high temperature in several processes. [16,17] (b) High toughness to withstand bending and packaging for flexible printed circuit boards. Hard and soft segment are incorporated into the PI to enhance ultimate tensile stress (UTS) and elongation at break (ε b ), simultaneously for achieving high toughness.…”