Poly(arylene ether)s with Low Refractive Indices: Poly(biphenylene oxide)s with Trifluoromethyl Pendant Groups via a Meta-Activated Nitro Displacement Reaction

Soluble Poly(amide-imide)s from Diamide–Diamine Monomer with Trifluoromethyl Groups

A series of soluble aromatic poly(amide-imide)s (PAIs) was prepared from a new diamide–diamine monomer having biphenyl units with two CF₃ groups. The diamide–diamine monomer was polymerized with 2,2′-bis(trifluoromethyl)benzidine and pyromelltic dianhydride through an imidization reaction to prepare PAIs with a controlled imide/amide bond ratio in the main chains. While the PAIs with the highest imide bond content showed a limited solubility, other PAIs were soluble in polar organic solvents and can be solution-cast into flexible freestanding films. All PAIs exhibited high thermal stability with 5% weight loss temperature (T_d5) from 464 to 497 °C in air, and no appearance of glass transition up to 400 °C. Notably, the linear coefficient of thermal expansion (CTE) value of the PAI films was linearly decreased with the imide bond content and varied from 44.8 to 7.8 ppm/°C.

Poly(amide-imide) materials for transparent and flexible displays

The key component currently missing for the next generation of transparent and flexible displays is a high-performance polymer material that is flexible, while showing optical and thermal properties of glass. It must be transparent to visible light and show a low coefficient of thermal expansion (CTE). While specialty plastics such as aromatic polyimides are promising, reducing their CTE and improving transparency simultaneously proved challenging, with increasing coloration the main problem to be resolved. We report a new poly(amide-imide) material that is flexible and displays glass-like behavior with a CTE value of 4 parts per million/°C. This novel polymer was successfully used as a substrate to fabricate transparent and flexible indium-gallium-zinc oxide thin-film transistors.

Postpolymerization of a fluorinated and reactive poly(aryl ether): an efficient way to balance the solubility and solvent resistance of the polymer

A new fluorinated poly(aryl ether) with reactive benzocyclobutene groups as the side chain was successfully synthesized. This polymer showed a number-average molecular weight (Mn) of 200,000 and had good solubility and film-forming ability. After being postpolymerized at high temperature (>200 °C), the polymer film converted to a cross-linked network structure, which was insoluble in the common organic solvents. Such results suggest that the postpolymerization is an efficient way to achive the balance between the solubility and the solvent resistance of the polymer. TGA data showed that the postpolymerized polymer had a 5 wt % loss temperature at 495 °C and a residual of 61% at 1000 °C under N2. The cross-linked film also exhibited good dielectric properties with an average dielectric constant of about 2.62 in a range of frequencies from 1 to 30 MHz. With regard to the mechanical properties, the cross-linked film had hardness, Young's modulus, and bonding strength to a silicon wafer of 1.22, 8.8, and 0.89 GPa, respectively. These data imply that this new polymer may have potential applications in the electrical and microelectronics industry.