Exploring the potential of thin films made from poly(imide-amide-sulfone)s for engineering applications

Highlights: • Amorphous free-standing thin poly(amide-imide-sulfone) films are investigated. • Most films display good transparency beyond 500 nm, with transmittance of about 80%. • They are tough and highly flexible, allowing easy stretching, bending or rolling. • The films are insulators, with dielectric constant between 2.4 and 3.9 at 1 Hz. • The polymers with reduced concentration of amide units are much permeable to gases. This work focuses on the thorough investigation of structure–assisted multifunctional properties of some poly(amide-imide-sulfone) films specifically designed to meet the technological needs. In this respect, the influence of structural parameters onto mechanical, optical, dielectric and gas transport properties was deeply explored along with some general characteristics, like chemical integrity, thermal stability and solid-state packing. The understudy tough and flexible films featuring amorphous state displayed good mechanical behavior, withstanding repeating bending or rolling. The sulfone groups reduced the charge transfer complex formation, and in some cases, increased transparency. The permittivity, dielectric loss and conductivity and their variation with frequency and temperature were studied along with γ and β secondary relaxations originating from small- and large-scale segmental motions. The permeability of CO₂, O₂ and N₂ through these dense films along with diffusion and solubility coefficients and respective selectivities were measured and discussed in relation with the structural parameters.