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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. [ABSTRACT FROM AUTHOR]

Polyimides (PIs) with super heat‐resistance and ultralow coefficient of thermal expansion (CTE) are required urgently to employ as plastic substrates in flexible‐display devices. To attain the target properties, we designed and synthesized a novel bibenzimidazole diamine characterized in having a N‐phenyl group, namely 1‐phenyl‐2,2′‐bibenzoimidazole‐5,5′‐diamine (PhDABZ), and focused on an aromatic poly(benzimidazole imide) series derived from 1,2,4,5‐benzenetetracarboxylic (PMDA). Incorporating bibenzimidazole and N‐substituent effectively increase the interchain interaction and chance for flexible film formation, which provides the PIs with high glass‐transition temperature (Tg > 480 °C) and dimensional stability (CTE < 10 ppm K−1). These data provide a feasible method to achieve higher thermal properties of PIs. [ABSTRACT FROM AUTHOR]

Novel diamines containing spirobisbenzoxazole scaffold structure were successfully synthesized. These diamines were homopolymerized with commercial 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and cyclohexanedianhydride (H'PMDA) to prepare a series of benzoxazole based polyimides (PBOIs). The obtained PBOIs exhibited good organic solubility and outstanding thermal properties, including glass transition temperature (T g) of 355–400 °C and 5% thermal decomposition temperatures (T d5%) of 474–490 °C. Meanwhile, these polymer films exhibited excellent mechanical strength, such as tensile strength of 79.4–92.1 MPa and elongation at break of 19.5%∼31.2%. In addition, such PBOIs have been proved to be novel microporous polymer with pore width distribution of 5–7 Å and BET surface area of 281–378 m2/g. The permeability-selectivity relationship of H'PMDA based PBOIs was close to the 2008 Robeson upper bound for CO 2 /CH 4 and O 2 /N 2 gas pairs, showing promise in the field of gas separation. [Display omitted] • Spirobibenzoxazole scaffold based Polyimides. • Good solubility and microporosity. • The permeability-selectivity relationship of H'PMDA based polyimides for CO 2 /CH 4 and O 2 /N 2 gas pairs close to the 2008 Robeson upper bound. [ABSTRACT FROM AUTHOR]

To prepare colorless polyimides (CPIs), two novel diamines, namely 6-amino-2-(2′-methyl-4′-aminobenzene)-N-phenylbenzimidazol (5a) and 6-amino-2-(2′-trifluoromethyl-4′-aminobenzene)-N-phenylbenzimidazol (5b) were synthesized, and two series of polyimides derived from them were developed. Except for the inherent asymmetric structures, the twisted moieties had been successfully incorporated in the benzimidazole dianmines through 2′- and N-substituents. The loose chain packing and hindered charge transfer (CT) interaction caused by the askew and distorted segments provided the polyimides with excellent optical transparency (80% transmittance at 400 nm, semi-alicyclic series), while the resulting films inherited the unique superheat-resistance of poly(benzimidazole imide)s (PBIIs), e.g., high glass-transition temperatures (up to 402 °C). Such outstanding optical and thermal properties expanded their application as heat-resistant colorless materials. Furthermore, the correlation between various 2′-substituents and characters of these PBII films was systematically analyzed. These data indicated that these colorless polyimides had potential application as optical and optoelectronic materials. [Display omitted] • Two novel benzimidazole dianmines containing 2′- and N-substituents (5a and 5b) were successfully synthesized. • Polyimide films with asymmetric and twisted structures were successfully synthesized. • The semi-aromatic poly(benzimidazole imide) films achieved colorlessness (T 400 = 80–81% and T g = 394–402 °C). • The effect of various 2′-substitutions on the properties of these N-phenyl-poly(benzimidazole imide)s was investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel spirobisbenzoxazole-based polyimides of intrinsic microporosity were prepared. • The polyimides showed good solubility, excellent thermal and mechanical properties. • Discuss the rotation restriction and thermal annealing process on gas permeation behavior. Improving the processability and permeability of aromatic polyimides is a prerequisite for promoting the application in the field of gas separation membranes. Here, a series of novel spirobisbenzoxazole-based polyimides were synthesized. The novel spirobisbenzoxazole unit showed a larger rigid step size than the reported spirobisindane unit, which more effectively destroyed the molecular packing. As a result, the obtained aromatic polyimides showed good organic solubility and significantly improved gas permeability. Such polyimides were also considered as polymers of intrinsic microporous (PIMs) with ultra-micropore distribution of 5 ∼ 7 Å and high BET surface areas ranging from 373 to 449 m2/g. Meanwhile, the obtained polyimide membranes exhibited excellent thermal properties (T g > 400 °C) and outstanding mechanical properties (σ > 100 MPa). The effects of rotation restriction and thermal annealing process on gas permeation behavior were also studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Poly(benzimidazole imide) films with asymmetric and twisted structures was successfully synthesized. • These poly(benzimidazole imide)s achieved more prominent properties than traditional poly(benzimidazole imide)s. • The semi-aromatic poly(benzimidazole imide)s were expected to be expanded as heat-resistant colorless materials. • The effect of various 2′-substitutions on the properties of these poly(benzimidazole imide)s was discussed. To prepare colorless polyimide (CPI) films with high thermal properties, an effective design strategy is incorporating asymmetric and twisted structures in the polymer chain-segments. Based on this strategy, 6,4′-diamino-2′-methyl-1-methyl-2-phenylbenzimidazole (5a) and 6,4′-diamino-2′-trifluoromethyl-1-methyl-2-phenylbenzimidazole (5b) were synthesized, and two series of their polyimides (semi- and fully aromatic series) were prepared, respectively. The obtained poly(benzimidazole imide)s (PBIIs) with loosely packed but rigid backbones possessed not only high glass transition temperature (T g) but also improved optical transparency. In particular, the semi-aromatic system achieved an excellent transmittance about 80% at 400 nm and an outstanding T g exceeding 400 °C. Furthermore, the influence of various 2′-substitutions on the combination properties of these poly(benzimidazole imide)s was systematically analyzed. These data expand the poly(benzimidazole imide)s as optical materials and provide a feasible method to prepare heat-resistant colorless polymers. [ABSTRACT FROM AUTHOR]