Figure 5. Sonication of copolymers of DCTCU with epoxide (6) and cis-gDCC (8).

(a,b) Primary chemical reactions resulting from sonication of 6 (a) and 8 (b). Sonication of 8 leads to ring opening of gDCC gated within the initial DCTCU (blue fragment in 9) and ungated along the polymer backbone (red fragment). (c) Partial ¹H NMR spectrum of polymer 6 before (black) and after (green) sonication. (d,e) Molar fractions of isomerized DCTCU moieties (blue, polymers 6 and 8) and backbone gDCC moieties (red, polymer 8 only) as a function of sonication time of polymer 6 (d) and 8 (e). As is typical for every other polymer reported, non-selective backbone fragmentation competes with mechanophore-centered chemistry during sonication of polymers 6 and 8, decreasing their average molecular weights (black axes and Supplementary Figs 8 and 9). Error bars are standard deviations.