The mechanical conversion of all three polymers PMA1-PMA3 rapidly approached completion after about 20 min ultrasonication, whereas there were minor changes in their polymer molecular weights over the same period as indicated by size exclusion chromatography (SEC) (Figure ). This highlights another feature of the diarylethene mechanophores that their noncovalent-yet-chemical transformation signals stress without sacrificial bond scission, minimizing the impact on the intrinsic properties of the polymer matrix. Additionally, control polymers containing M1-M3 at PMA chain ends remained photoinert before and after identical ultrasound treatments, confirming the mechanical origin of the observed changes from ultrasonication experiments (Figure ).