Encoding Force-Responsive Speed Bumps Into Slide-Ring Networks for Programmable Mechanical Properties

Abstract

Slide-ring (SR) materials exploit mobile crosslinkers to achieve exceptional toughness and fatigue resistance via the “pulley effect.” However, macrocycle sliding in conventional SR networks remains passive and unregulated, lacking the ability to temporally or spatially program energy dissipation. Inspired by station-regulated shuttling in molecular machines, we introduce mechanically gated “speed bumps” into SR architectures. Here, we report a mechanically interlocked polyurethane network PU-DP-TED-a, in which pillar[5]arene-based macrocycles (DP) function as sliding crosslinkers and strategically positioned Diels–Alder adducts (TED) act as force-labile speed bumps along the polymer axle. Under tension, macrocycles are pushed against TED units, triggering a retro-Diels–Alder reaction that transiently arrests ring sliding and dissipates mechanical energy. This force-triggered, sequential “arrest-and-release” mechanism provides spatiotemporal control over energy dissipation. Relative to a non‑interlocked control containing TED but no DP, the resulting material exhibits a rare combination of enhancements: Young's modulus increases by 9.9‑fold (from 3.46 to 34.2 MPa), tensile strength by 6.0‑fold (from 3.28 to 19.8 MPa), elongation at break by 2.9‑fold (from 155% to 449%), and toughness by 16.6‑fold (from 3.74 to 62.0 MJ m⁻³). This work establishes a paradigm for active, force‑programmable SR materials with multi‑stage energy dissipation and adaptive mechanical behavior.