Figure 3.

Mechanically triggered release of (a) hydroxycoumarin and (b) aminocoumarin from polymers as a function of mechanophore substitution. Polymer solutions (2 mg/mL in 3:1 MeCN/MeOH) were sonicated for 60 min (“on” time), warmed to room temperature, and the release of coumarin cargo from the mechanically liberated 2-furylcarbinol derivatives was monitored by photoluminescence spectroscopy. PL parameters: λ_ex = 330 nm, λ_em = 378 nm (hydroxycoumarin); λ_ex = 365 nm, λ_em = 424 nm (aminocoumarin). The initial PL intensity was subtracted from each measurement and the data were normalized to the plateau value. For PMA-3(NH), the data were normalized assuming 36% mechanophore activation; the black dashed line represents a first-order reaction with a half-life of 240 days.