Abstract
Flexible displays are a systematic revolution in the field of display, in which high-performance and high-barrier polymer substrates are considered to be one of the most important key materials. In this work, high water vapor barrier polyimides containing amide moieties were synthesized via the ternary polymerization of 4,4′-diaminobenzailide (DABA), 4,4′-diaminodipheny ether (ODA), and 3,3′,4,4′-biphenyl-tetracarboxylic acid dianhydride (BPDA) followed by thermal imidization. The relationship between the content of amide moieties and the water vapor barrier property of the prepared polyimides was studied by means of density test, water absorbing test, water contact angle test, water vapor permeation test, fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), thermogravimetry coupled with fourier transform infrared spectrometry (TG-FTIR), wide-angle X-ray diffraction analysis (WXRD), mechanical performance test, etc. The results show that the introduction of amide groups into polyimide (PI) main chains can improve the water vapor barrier properties of the polyimides effectively. The water vapor transmission rate (WVTR) of the polyimide films can be improved from 8.2365 g·(m2·24 h)−1 to 0.8670 g·(m2·24 h)−1 with the increasing content of amide moieties.
Highlights
The leading development trend of modern electronic products is miniaturization, integration, and portability [1,2]
To water investigate infrared mechanisms, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), (FT-IR), thermogravimetric analysis (TGA), and thermogravimetry coupled with fourier transform and thermogravimetry coupled with fourier transform infrared spectrometry (TG-FTIR)
The amide-containing polyimides were synthesized using a two-step method by the copolymerization of ODA and biphenyltetracarboxylic dianhydride (BPDA) with an amide-containing diamine DABA, as shown in Scheme 1
Summary
The leading development trend of modern electronic products is miniaturization, integration, and portability [1,2]. High-performance polymer-based flexible substrates—especially high-barrier polymer substrates—are considered to be one of the most important key materials. They play important roles in the environmental protection and mechanical support for the devices [3–10], and are one of the main factors affecting the lifetime of devices [11–16]. Among the traditional polymer-based substrates (Table 1), polyimides are widely used as electronic packaging and electrical insulation materials in the field of aerospace industries and microelectronics [26–28]. They are considered to be the most promising candidates for the flexible substrates of flexible displays because they are thermally stable under high processing temperature. The existence of free volume in polymer materials makes them essentially permeable [29–36], limiting their applications as barrier materials in the field of flexible
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