Force-Programmed Evolution of Topological Freedom in Slide-Ring Polymer Networks
Abstract
Force-adaptive polymer networks, whose mechanical response evolves under load, offer a route to structural materials that combine high stiffness and strength with efficient energy dissipation.[1,2] Most existing force-adaptive systems achieve this through mechanochemical reactions that generate reactive intermediates and thereby stiffen or rearrange the network,[3-5] a strategy that is intrinsically limited by diffusion, reaction kinetics, and the irreversible consumption of the reactive species. Here we pursue a fundamentally different strategy, in which a force-triggered transformation regulates the topological freedom of a slide-ring crosslink[6,7] rather than driving a chemical reaction. We integrate a mechanophore directly into the stopper of a rotaxane crosslinker, in which a cyclobutane formed by the [2+2] photodimerization of two cinnamate units[8,9] acts as the bulky stopper that confines a 24-crown-8 macrocycle on a dibenzylammonium axle.[10,11] Under load, retro-[2+2] cycloreversion reduces the steric dimension of the stopper and thereby expands the sliding space accessible to the macrocycle, so that a single covalent event gates a large slidingdissipation channel rather than dissipating energy directly. We incorporated this crosslinker into a segmented polyurethane and evaluated it against an orthogonal three-member sample set (R, C1, C2) of identical crosslinker content that decouples whether the stopper can open from whether the macrocycle can slide. The optimal composition, R3, reaches a toughness of about 215 MJ m-3 and a tensile strength of about 38 MPa—up to 9.4 and 5.6 times the toughness and strength of the openbut-cannot-slide control (C1), and far exceeding the constitutively sliding control (C2). Smallstrain dynamic mechanical analysis confirms that the mechanophore is silent at low strain, whereas gradient cyclic loading reveals a force-activation fingerprint: the dissipation ratio of R3 rises from below both controls at 100% strain to above them at high strain, crossing over near 300–400%. Infrared spectroscopy detects the regenerated cinnamate C=C band only after stretching and only in the cyclobutane-bearing samples,[8,9] and an annealing-reload test shows that the extra dissipation of R3 is largely recoverable with the smallest permanent damage of the three, consistent with a reversible sliding channel that shields the matrix.[12,13] These results establish a general design principle in which the structural precision of a mechanochemical transformation programs the evolution of topological freedom during deformation.
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BibTeX
@misc{yu2026forceprogrammed,
title = {{Force-Programmed Evolution of Topological Freedom in Slide-Ring Polymer Networks}},
author = {Chenjuan Yu and Yuping Wang},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008824/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008824/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Force-Programmed Evolution of Topological Freedom in Slide-Ring Polymer Networks
AU - Chenjuan Yu
AU - Yuping Wang
PY - 2026
DA - 2026/09/14
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008824/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008824/v1
AB - Force-adaptive polymer networks, whose mechanical response evolves under load, offer a route to structural materials that combine high stiffness and strength with efficient energy dissipation.[1,2] Most existing force-adaptive systems achieve this through mechanochemical reactions that generate reactive intermediates and thereby stiffen or rearrange the network,[3-5] a strategy that is intrinsically limited by diffusion, reaction kinetics, and the irreversible consumption of the reactive species. Here we pursue a fundamentally different strategy, in which a force-triggered transformation regulates the topological freedom of a slide-ring crosslink[6,7] rather than driving a chemical reaction. We integrate a mechanophore directly into the stopper of a rotaxane crosslinker, in which a cyclobutane formed by the [2+2] photodimerization of two cinnamate units[8,9] acts as the bulky stopper that confines a 24-crown-8 macrocycle on a dibenzylammonium axle.[10,11] Under load, retro-[2+2] cycloreversion reduces the steric dimension of the stopper and thereby expands the sliding space accessible to the macrocycle, so that a single covalent event gates a large slidingdissipation channel rather than dissipating energy directly. We incorporated this crosslinker into a segmented polyurethane and evaluated it against an orthogonal three-member sample set (R, C1, C2) of identical crosslinker content that decouples whether the stopper can open from whether the macrocycle can slide. The optimal composition, R3, reaches a toughness of about 215 MJ m-3 and a tensile strength of about 38 MPa—up to 9.4 and 5.6 times the toughness and strength of the openbut-cannot-slide control (C1), and far exceeding the constitutively sliding control (C2). Smallstrain dynamic mechanical analysis confirms that the mechanophore is silent at low strain, whereas gradient cyclic loading reveals a force-activation fingerprint: the dissipation ratio of R3 rises from below both controls at 100% strain to above them at high strain, crossing over near 300–400%. Infrared spectroscopy detects the regenerated cinnamate C=C band only after stretching and only in the cyclobutane-bearing samples,[8,9] and an annealing-reload test shows that the extra dissipation of R3 is largely recoverable with the smallest permanent damage of the three, consistent with a reversible sliding channel that shields the matrix.[12,13] These results establish a general design principle in which the structural precision of a mechanochemical transformation programs the evolution of topological freedom during deformation.
ER -