Dual crosslinking polymer networks: correlation between polymer topologies and self-healing efficiency

The topologies of polymers can impact the performance of polymeric materials, including their chemical and physical properties. In this work, a dynamic covalent bond of boronate ester was introduced by the addition of 4-vinylphenylboronic acid to the rich hydroxyl groups of polyglycidols (PGs) with different topologies, including branched cyclic, hyperbranched, and linear PGs. The formation of the dual crosslinked polymer networks, which consisted of dynamic covalent bonds (B-O) and static covalent bonds, was confirmed by thermogravimetric analysis and a swelling test. In addition, the mechanical properties of the cured materials were evaluated using a rheometer, dynamic mechanical analysis, and nanoindentation. Scratch tests and tensile tests were used to determine the self-healing effectiveness of polymer topologies. Intriguingly, based on the polymer topologies, the crosslinked network with a branched cyclic structure (bc-cPGB) exhibited a greater self-healing efficiency and modulus than hyperbranched networks (hb-cPGB). These findings indicate that the physical properties of polymer networks are influenced by the network mesh space and preferred intermolecular crosslinking of the branched cyclic structure. In addition, to maximize the benefits of the dual crosslinking system, the dynamic B-O bonds were utilized for recycling cured materials, and the PG prepolymer was successfully recovered from cPGB by adding pinacol to THF with a yield of 99.5%. These findings demonstrate the significance of topology control in highly adaptable advanced functional materials.