Is Molecular Weight or Degree of Polymerization a Better Descriptor of Ultrasound-Induced Mechanochemical Transduction?
A detailed understanding of the fundamental processes that govern mechanical transduction in covalent polymer mechanochemistry is essential to advance innovation in this field. In contrast to progress in the development of new mechanophores, the influence of polymer structure and composition on mechanochemical activity has received relatively little attention. In order to address this gap in knowledge, a continuous flow system with synchronous UV–vis absorption capabilities was designed to quantify the ultrasound-induced mechanical activation of a spiropyran mechanophore in real-time. Measurements of reaction kinetics with polymer tethers of varying repeating unit structure demonstrate that degree of polymerization is the key descriptor of mechanochemical activity, independent of molecular weight and pendant group constitution. These results have important implications for the rationalization of mechanochemical properties and the design of new mechanochemically active polymer systems.
Additional Information© 2016 American Chemical Society. CS Editors' Choice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: November 25, 2015. Accepted: January 7, 2016. Published: January 17, 2016. This work was supported in part by the National Science Foundation (DMR 1307354) and a ARO MURI (W911NF-07-1-0409). The authors thank Dr. Charles Diesendruck, Dr. Matt Kryger, and Dr. Koushik Ghosh for helpful discussions and Dorothy Loudermilk for assistance with graphics. M.J.R. gratefully acknowledges the Arnold and Mabel Beckman Foundation for a Beckman Institute Postdoctoral Fellowship. The authors declare no competing financial interest.
Published - acsmacrolett.5b00855.pdf
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