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

Abstract

To introduce intramolecular hydrogen bonds in the polyimides (PIs), 5(6)‐amino‐2‐(5‐aminopyridin‐2‐yl)‐benzimidazole (PyPABZ) were designed and synthesized. The intramolecular interaction was indicated by Fourier transform infrared when different copolyimides were prepared with 4,4′‐oxydianiline and PyPABZ. These modified poly(benzimidazole imide)s eliminate the problem of high water absorption for benzimidazole (BI)‐containing PIs in the materials applications. Moreover, the high packing coefficient and rigidity of these copolyimides caused by the strong intramolecular interaction from the H‐bonding and the resulting PIs exhibited outstanding thermal properties such as high glass‐transition temperature (Tg) and low coefficient of thermal expansion.

Heat‐resistant polyimides with lowCTEand water absorption through hydrogen bonding interactions

“…Meanwhile, different from the two chemical shifts of amine proton hydrogen in PABZ, the amine proton hydrogen of DPABZ showed a single chemical shift, indicating the amine group of the latter would contribute equivalent reactivity in the subsequent polymerization reaction. It is worth noting that DPABZ showed split protons in the 1 H NMR spectrum caused by isomers of BI 15,19 . The amine proton hydrogen attached on BI showed more shielded than benzene ring, indicating the N atom of former showed higher nucleophilicity than latter 20 …”

“…It is worth noting that DPABZ showed split protons in the 1 H NMR spectrum caused by isomers of BI. 15,19 The amine proton hydrogen attached on BI showed more shielded than benzene ring, indicating the N atom of former showed higher nucleophilicity than latter. 20 Furthermore, the molecular modeling of PABZ and DPABZ were optimized by DFT 12,13,15 (Figure 2).…”

“…Compared with traditional PABZ (5-amino-2-[4-aminoben-zene]benzimidazole), 12,13,17 more BI moieties in diamine segments were hope to provide more proton donors and amines attached on BI were expected to strengthen electron donation-acceptance interaction. Due to special molecular structure, 18,19 DPABZ also had the possibility of forming intramolecular hydrogen bonding, which behaved the potential to improve the hydrophobicity of polymers. Two series of copolyimide films based on PABZ or DPABZ were prepared by copolycondensation with 4,4-diaminodiphenyl ether (ODA) and 4,4-biphthalic anhydride (BPDA).…”

N-Phenyl-substituted poly(benzimidazole imide)s with high glass transition temperature and low coefficient of thermal expansion

“…Unfortunately, the benzimidazolecontaining polyimides generally display a high water absorption (W A ) because of the hydrogen-bonded water molecule formation, which may cause a series of application issues, such as package cracking, metal corrosion and degradation of dielectric properties. 13,14 Additionally, their intermolecular Hbonding and rigid backbone reduce the exibility of PBII lms, resulting in the high brittleness of the series derived from fully rigid pyromellitic dianhydride (PMDA), 7,15 whereas aromatic PMDA-based polyimides are usually superheatresistant. 16,17 In our previous discussion, it was pointed out that modied poly(benzimidazole imide)s without intermolecular H-bonding can achieve good comprehensive performance, e.g., lighter color and lower H 2 O-absorption.…”

Homopolyimides containing both benzimidazole and benzoxazole with highTgand low coefficient of thermal expansion

“…The CTE values of the PIs were in the range of 1.3-20.9 ppm/ C from 50 to 250 C, which were much lower than the commercially available PIs (30-50 ppm/ C). The introduction of benzoazole unit significantly reduced the CTE of the derived PI films, 7,39 and even the CTE values of 3a-BPDA and 3b-BPDA were lower than silicon wafers (about 5 ppm/ C), reaching 1.3 and 3.1 ppm/ C, which can already meet most process environments. It should be pointed out that when the testing temperature higher than the T g of the polymers, the dimension of the polymer changed drastically, which was due to a transition from glassy state to rubbery state of polymers, and segments can move freely.…”