Controlled functionalization of poly(4-methyl-1-pentene) films for high energy storage applications

Abstract

A new family of poly(4-methyl-1-pentene) ionomer [PMP-(NH₃)_xA-y] (x = 1, 2, 3 and A = Cl⁻, SO₄²⁻, PO₄³⁻, y = NH₃ content) modified (NH₃⁺)_xA^x− ionic groups has been synthesized. The ionomers were synthesised using either a traditional Ziegler–Natta or a metallocene catalyst for the copolymerisation of 4-methyl-1-pentene and bis(trimethylsilyl)amino-1-hexene. A systematic study was conducted on the effect of the subsequent work-up procedures that can prevent undesirable side reactions during the synthesis of the [PMP-(NH₃)_xA-y] ionomers. The resulting PMP-based copolymers were carefully monitored by a combination of nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), mechanical properties, dielectric properties, and electric displacement–electric field (D–E) hysteresis loop measurements. Our results reveal that the [PMP-(NH₃)_xA-y] ionomer films show a significantly enhanced dielectric constant (∼5) and higher breakdown field (∼612 MV m⁻¹) as compared with pure PMP films. Additionally, these PMP-based films show good frequency and temperature stabilities (up to 160 °C). A reliable energy storage capacity above 7 J cm⁻³ can be obtained, and is twice the energy storage capacity of state-of-the-art biaxially oriented polypropylene films, which can be attractive for technological applications for energy storage devices.