Fig. 4. Unwinding mechanism and thermal stability of AMM ±n.

a, Chemical composition of an equilibrated ±n sample (left), a sample at PSS (middle left), without addition of external nucleophile (middle right) and after relaxation at 10 °C for 60 h with 20 mol% of nBuNH₂ (right). Full relaxation at 10 °C only occurs in the presence of nucleophiles. b, Proposed mechanism for the thermal relaxation of wound up ±n via temporary ring-opening in the presence of catalytic amounts of nucleophile. c,d, Representative examples for the relaxation kinetics of an irradiated ±n sample at 10 °C in the presence of 20 mol% of nBuNH₂ (c) and without nucleophiles (d). The chemical composition (a) and kinetic profiles (c,d) were obtained by ¹H-NMR spectroscopy (500 MHz, 10 °C, 1 mM in C₆D₆).