A universal strategy for flaw-insensitive nanocomposite eutectogels with centimeter-scale fractocohesive length using multi-crosslinkable polyhedral oligomeric silsesquioxane (POSS)

Abstract

Eutectogels have become sustainable alternatives in the field of flexible electronics due to their environmentally friendly, extreme-temperature-resistant and cost efficiency. However, their susceptibility to crack propagation under deformation remains a critical limitation for engineering applications. Herein, a new crack-resistant nanocomposite eutectogel containing an inhomogeneous polymer network and rigid nanoparticle core by using polyhedral oligomeric silsesquioxane (POSS) as multifunctional crosslinkers is designed. The resulting POSS-based eutectogel demonstrates a centimeter-scale fractocohesive length of 1.19 cm, which is the highest ever recorded for synthetic eutectogels, and high fracture toughness of 3934 J/m². Notably, the incisions of the POSS-based eutectogel remained virtually unchanged after 1000 tensile cycles. The exceptional crack resistance originates from a synergistic mechanism between an architectured inhomogeneous network and a rigid nanoparticle core. When the POSS-based eutectogel is stretched, the chain-dense regions in the network act as the first barrier to resist the stress at the crack tip; subsequently, the nanoscale rigid POSS core acts as the second barrier to further resist stress and prevent crack propagation. This crack-resistant design strategy is universal and has been successfully extended to various eutectogel systems, including polyacrylamide eutectogel and poly (hydroxyethyl methacrylate) eutectogel. In addition, the POSS-based eutectogel possesses low hysteresis, strong adhesion and antifreeze properties (down to −40 °C). The flexible sensors based on this eutectogel exhibit stable strain responses at both ambient and low temperatures. This work provides an innovative design strategy for defect-tolerant and extreme-environment-resistant flexible devices.