Imparting Ultrahigh Strength to Polymers via a New Concept Strategy of Construction of up to Duodecuple Hydrogen Bonding among Macromolecular Chains

Abstract

Interconnecting macromolecules via multiple hydrogen bonds (H‐bonds) can simultaneously strengthen and toughen polymers, but material synthesis becomes extremely difficult with increasing number of H‐bonding donors and acceptors; therefore, most reports are limited to triple and quadruple H‐bonds. Herein, this bottleneck is overcome by adopting a quartet‐wise approach of constructing H‐bonds instead of the traditional pairwise method. Thus, large multiple hydrogen bonds can be easily established, and the supramolecular interactions are further reinforced. Especially, when such multiple H‐bond motifs are embedded in polymers, four macromolecular chains—rather than two as usual—are tied, distributing the applied stress over a larger volume and more significantly improving the overall mechanical properties. Proof‐of‐concept studies indicate that the proposed intermolecular multiple H‐bonds (up to duodecuple) are readily introduced in polyurethane. A record‐high tensile strength (105.2 MPa) is achieved alongside outstanding toughness (352.1 MJ m−3), fracture energy (480.7 kJ m−2), and fatigue threshold (2978.4 J m−2). Meantime, the polyurethane has acquired excellent self‐healability and recyclability. This strategy is also applicable to nonpolar polymers, such as polydimethylsiloxane, whose strength (15.3 MPa) and toughness (50.3 MJ m−3) are among the highest reported to date for silicones. This new technique has good expandability and can be used to develop even more and stronger polymers.