Topology-Dependent Glass Formation Behavior in Poly[n]catenane Melts with Variable Ring Size and Chain Length
Abstract
Poly[n]catenanes consist of cyclic subunits that are connected by mechanical bonds rather than covalent bonds, which gives them internal degrees of freedom and permanent topological constraints that are absent in conventional polymers. How these features affect the glass transition is not known. Here, we employ molecular dynamics simulations of the Kremer–Grest bead–spring model to determine the glass transition temperature, Tg, of poly[n]catenane melts with ring sizes of m = 8–50 beads and chain lengths of n = 5–40 rings. Each melt is compared with a bonded-ring analogue in which the mechanical link between neighboring rings is replaced by a covalent bond. Mechanical interlocking raises Tg by up to 0.44 εk B -1 , nearly a factor of 2, for the smallest rings, whereas the effect vanishes for m ≥ 20. This crossover coincides with the ring size at which the free aperture of a ring, measured in the melt, falls below one bead diameter. The topological contribution to Tg scales as 1 − n end /n with n end ≈ 2.1 for all tightly interlocked chains, indicating that the two singly interlocked terminal rings act as topological chain ends. The Debye–Waller factor, the generalized localization model, and the non-Gaussian parameter show that tight mechanical bonds restrict bead motion at a given temperature, make the relaxation time grow more steeply as the cage tightens, and add a broad, slow, and strongly non-Gaussian component to segmental relaxation. In contrast, the dynamic fragility and the large-scale Gaussian chain statistics are nearly unaffected, and the modest increase of the characteristic ratio cannot account for the rise of Tg. Our work identifies ring size as the primary molecular parameter controlling the glass transition of poly[n]catenanes and shows that it acts through local topological confinement rather than global chain stiffness.
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BibTeX
@misc{chen2026topologydependent,
title = {{Topology-Dependent Glass Formation Behavior in Poly[n]catenane Melts with Variable Ring Size and Chain Length}},
author = {Yuxiang Chen and Wei Li and Zhenghao Wu},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010248/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010248/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Topology-Dependent Glass Formation Behavior in Poly[n]catenane Melts with Variable Ring Size and Chain Length
AU - Yuxiang Chen
AU - Wei Li
AU - Zhenghao Wu
PY - 2026
DA - 2026/10/12
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010248/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010248/v1
AB - Poly[n]catenanes consist of cyclic subunits that are connected by mechanical bonds rather than covalent bonds, which gives them internal degrees of freedom and permanent topological constraints that are absent in conventional polymers. How these features affect the glass transition is not known. Here, we employ molecular dynamics simulations of the Kremer–Grest bead–spring model to determine the glass transition temperature, Tg, of poly[n]catenane melts with ring sizes of m = 8–50 beads and chain lengths of n = 5–40 rings. Each melt is compared with a bonded-ring analogue in which the mechanical link between neighboring rings is replaced by a covalent bond. Mechanical interlocking raises Tg by up to 0.44 εk B -1 , nearly a factor of 2, for the smallest rings, whereas the effect vanishes for m ≥ 20. This crossover coincides with the ring size at which the free aperture of a ring, measured in the melt, falls below one bead diameter. The topological contribution to Tg scales as 1 − n end /n with n end ≈ 2.1 for all tightly interlocked chains, indicating that the two singly interlocked terminal rings act as topological chain ends. The Debye–Waller factor, the generalized localization model, and the non-Gaussian parameter show that tight mechanical bonds restrict bead motion at a given temperature, make the relaxation time grow more steeply as the cage tightens, and add a broad, slow, and strongly non-Gaussian component to segmental relaxation. In contrast, the dynamic fragility and the large-scale Gaussian chain statistics are nearly unaffected, and the modest increase of the characteristic ratio cannot account for the rise of Tg. Our work identifies ring size as the primary molecular parameter controlling the glass transition of poly[n]catenanes and shows that it acts through local topological confinement rather than global chain stiffness.
ER -