Resilient and reprocessable physical gels based on crystalline olefin block copolymer elastomer and mineral oil toward optically transparent electronic packaging

Abstract

Due to the urgent demand of high-performance electronic packaging materials, thermoplastic elastomer physical gels (TPEG) have emerged as a promising alternative to traditional hydrogels and crosslinked rubbers due to their good thermal stability and reprocessability. In this work, olefin block copolymer (OBC) elastomer was blended with soft-block selective mineral oil (MO) to tune the mechanical property and transparency. It was found that the MO molecules can disperse well within amorphous phase with effective filling ratio ranging from 9.85 wt% to 44.82 wt%. The hard segments pack into spherulites and gradually develop into segregated crystals of ∼800 nm with the increase of MO concentration. Interestingly, fast quenching induces breakout crystallization morphology while thermal annealing at 130 °C can result in confined crystallization morphology with increased domain spacing due to the selective distributed MO since the corrected crystallinity remains constant and the crystal structure maintains as orthogonal crystals. Due to the combined effect of weak mesophase separation and decreased crystal size, OBC gels has an increased transparency up to 80% in visible region. The extensibility and cyclic property of OBC-based TPEG were finely tuned along with high transparency and excellent dielectric insulation property. Furthermore, the OBC gels are highly stable over a wide temperature and can be recycled. Overall, our work highlights the potential of thermoplastic elastomer physical gels as a sustainable and high-performance alternative for transparent electronics packaging materials.