High‐Temperature Oxidation‐Resistant Phenolic‐Based Hybrids Enabled by Novel Organic–Inorganic Covalent–Ionic Bicontinuous Network

Abstract Organic–inorganic thermosetting hybrids, featuring unique self‐ceramization abilities and excellent thermal‐oxidative stabilities, are garnering substantial interest as candidates for thermal protection in extreme environments. However, designing a groundbreaking hybrid with a molecular‐scale bicontinuous network remains a formidable challenge. In this work, a novel approach is proposed to prepare bicontinuous thermosetting hybrids with the aid of an organic–inorganic covalent–ionic molecule: 3‐carboxyphenylboronic acid (3‐CPBA) functionalized calcium phosphate oligomer (CPO), named 3‐BAPO. By tailoring the supramolecular interactions between 3‐BAPO and boron‐phenolic resin (BPR), a series of hybrid precursors is successfully obtained, designated 3‐BRPO, with varying inorganic contents (13.5–25.9 wt%). The hybrid precursors undergo concurrent inorganic ionic crosslinking and organic phenolic curing synchronously under reasonable conditions, resulting in the formation of a covalent‐ionic bicontinuous network. Multiple chemical interactions between the organic and inorganic components drive the formation of this network, imparting superior high‐temperature oxidation resistance to the 3‐BRPO hybrids, achieved by in situ ceramization of the continuous inorganic phase at ultrahigh temperatures. This work demonstrates a novel strategy to avoid the separate nucleation of the organic and inorganic phases in thermosetting hybrids by employing organic‐functionalized ionic oligomers as inorganic components, providing a promising platform for the molecular engineering of advanced hybrid materials.