Torsion effect of the imide ring on the performance of transparent polyimide films with methyl-substituted phenylenediamine

Abstract

On account of the urgent demands for wearable devices and flexible displays, the high transparency and heat-resistance of colorless polyimide (CPI) are required for its applicability and durability. Considering the...

Synthesis of novel biphenyl‐fused alicyclic tetracarboxylic dianhydride and its performance in thermostable and transparent colorless polyimides

“…1 H NMR (600 MHz, CDCl 3 , δ): (ppm) 7.57 (d, J = 1.8 Hz, 2H), 7.51 (dd, J = 7.9, 1.8 Hz, 2H), 7.45 (d, J = 7.9 Hz, 2H), 4.71 (d, J = 7.2 Hz, 8H). 13…”

“…However, it can generally afford only light color PIs with twist dianhydrides such as 3,3 0 -biphenyltetracarboxylic dianhydride (BPDA) 10 and aromatic diamines. We can see more examples of CPIs from the combination of 6FDA/alicyclic dianhydrides and aromatic diamines with bulky or twist side groups, such as 5(6)-amino-2-(4-aminobenzene)benzimid azole (PABZ), 11 2,2 0 ,2 00 ,3,3 00 ,5 0 -hexamethyl-[1,1 0 :4 0 ,1 00 -terphenyl]-4,4 00 -diamine (TP), 12 and tetramethyl-p-phenylenediamine (4-MpPDA) 13 (Scheme 1).…”

Synthesis and Characterization of Organo-Soluble Polyimides Based on Polycondensation Chemistry of Fluorene-Containing Dianhydride and Amide-Bridged Diamines with Good Optical Transparency and Glass Transition Temperatures over 400 °C

“…The experimental optical property results could be further verified by the frontier orbit simulation based on the DFT theory, as shown in Figure 10. It has been well established that the optical transparency of the donor-acceptor (D-A) polymers, such as PIs could be estimated by the energy gaps (∆ε) between the HOMO and LUMO energy levels in the polymers [43]. The larger the absolute ∆ε values, the less the degree of charge transfer (CT) interactions within the PI molecular chains, and the better the optical transmittance of the derived PI films.…”

Development of Fluorinated Colorless Polyimides of Restricted Dihedral Rotation toward Flexible Substrates with Thermal Robustness

“…The difficulty of achieving balanced desirable properties (thermal, optical, and mechanical) mainly lies in the intrinsic ambivalence of polymer structure–property relationships, involving its chemical and steric structures, macromolecular chain packing, and others. , The high optical transparency and low yellowness are acquired via introducing alicyclic (kink, spiro, cardo), − electronegative (–Cl, –F, –CF 3 ), − or bulky and bending moieties ,, in polyimide backbones. This loose chain packing in CPIs indeed contributes to the inhibition of intra- or interchain charge transfer complex (CTC) formation and improved transparency. , However, the dimensional stability (low CTE) and mechanical strength enhancement (high σ m and E t ) in the CPI system fundamentally require the dense packing of polymer chains, exhibiting marked contradiction with loose chain packing conditions for colorless transparency. , The well-known fluorine-containing CPI polymerized from 4,4′-(hexafluoroisopropylidene)­diphthalic anhydride (6FDA) and 2,2′-bis­(trifluoromethyl)­benzidine (TFMB) was designed and studied for the first time in the 1970s by Rogers et al and Harris et al, exhibiting excellent optical transparency (the transmittance at 400 nm, i.e., T 400 > 80%), high heat resistance ( T g = 335 °C, the temperature at 10% weight loss, viz., T d10% = 569 °C), and high thermal expansion (CTE = 48 ppm/K). − This rather high CTE is probably attributed to the flexible or twisted –C­(CF 3 ) 2 – unit of the 6FDA segments.…”