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

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.