Fig. 4: US-triggered activation of 2-furylcarbinol maleimide Diels-Alder adducts and fluorogenic cargo release.
From: Polymer microbubbles as universal platform to accelerate polymer mechanochemistry
a Scheme of mechanophore activation in the shell of PMB-PBL. b Optical micrograph of PMB-PBL; scale bar: 50 µm. The experiment was repeated three times, and similar images were obtained. c The decomposition mechanism of N3-A4 in polar protic solvent. d 1H NMR (400 MHz) characterization of the conversion of N3-A4 to N3-A3 and PBL (solvent: MeCN-d3:MeOH:H2O, 3:1:0.5; 5 mg N3-A4 in 0.5 mL solvent). e The time-dependent conversion of furfuryl carbonate N3-A4 by 1H NMR spectroscopy. f Fluorescence spectra of sonicated PMB-PBL in MeCN:MeOH:H2O (20 kHz, 12 W cm−2). g Photographs of samples under daylight and UV-light (λexc = 365 nm), (i) PMB-PBL solutions without sonication. (ii) MeCN/MeOH/H2O blank. (iii) The filtered solution of sonicated PMB-PBL (0.68 MHz). (iv) The filtered solution of sonicated PMB-PBL (20 kHz). h, i The release of fluorogenic cargo under 20 kHz and 0.68 MHz irradiation. Data are presented as mean values +/− the standard deviation. N = 3 independent sonications.
