Mechanical Reactivity of Two Different Spiropyran Mechanophores in Polydimethylsiloxane
We investigate the effect of pulling point location on the mechanochemical activation of two isomers of spiropyran in cross-linked polymeric materials through computational calculations and in situ fluorescence measurements. The threshold stress and strain required to activate the spiropyran mechanophores under tensile load are characterized. For both spiropyran isomers, applied stress favors the activated merocyanine states; however, despite differences in mechanochemical behavior predicted by quantum chemical calculations and previous single molecule experiments, both spiropyran isomers exhibit similar mechanochemical reactivity in bulk polymeric materials. The kinetics of the spiropyran–merocyanine transition under different tensile stresses are also examined. Overall, we find that varying the pulling geometry on the spiropyran mechanophore has only a minimal effect on the mechanical activation in bulk polymeric materials due to the complex nature of the macroscopic system.
Additional Information© 2018 American Chemical Society. Received: September 5, 2018; Revised: October 26, 2018; Published: November 8, 2018. This work was supported in part by the National Science Foundation (DMR 1307354). T.A.K. thanks the Kwanjeong Educational foundation for a fellowship. M.J.R. gratefully acknowledges the Arnold and Mabel Beckman Foundation for a Beckman Institute Postdoctoral Fellowship and startup funds from Caltech. The authors declare no competing financial interest.
Supplemental Material - ma8b01919_si_001.docx