The synergistic effect of nitrile and jeffamine structural elements towards stretchable and high-k neat polyimide materials

Abstract

In the attempt to develop polymeric materials with integrated functionalities for ever-expanding electronic applications, a facile and effective synthetic pathway towards high-k polyimide dielectrics which combine excellent thermostability, stretchability and surface adhesivity is reported. The synergistic effect of highly polar nitrile and jeffamine segments enabled the generation of amorphous semi-interpenetrating polymer networks (SIPNs) whose physico-chemical behavior was triggered by the grafting position of the nitrile unit on the aromatic hard segment. This was evident in various characteristics like solubility, morphology, thermal stability, mechanical strength and moreover, dielectric constant, conductivity, breakdown strength and energy density storage. The SIPN films were tough and highly stretchable, with a maximum strain at break of 516%, meanwhile self-sticky when they come in contact with each other or with other materials. The judicious structural variation in the nitrile-containing segment allowed modulation of the dielectric constant that reached 19 at 10⁶ Hz, which is among the highest reported to date for a neat polyimide material. The resulting SIPNs displayed noticeable breakdown strength, up to 220 V μm⁻¹, and energy storage density up to 1.092 J cm⁻³. A new insight into the molecular dynamics and charge carrier conductivity of these all-organic high-k polymer dielectrics is also provided to set the premises for use in stretchable electronics.