Abstracts Book - IMRC 2018

• SD1-O039
UNDERSTANDING MECHANOCHEMISTRY IN A TWO-
DIMENSIONAL PICTURE: WHICH FORCE BREAKS A BOND?
Michael Walter 1
1 Universität Freiburg, Center for Interactive Materials and Bioinspired Technologies, Germany.
The application of force on a material can enable reactions that are very
improbable or even impossible by usual thermochemistry. The action of
external forces on molecular reactions like bond breaking cannot be abstracted
thermal influences, however. Bonds break at one order of magnitude smaller
forces at usual temperatures than what would be expected a zero Kelvin
viewpoint - it is still temperature that breaks the bond. The force dependence of
the corresponding barriers is rather complex for non-trivial molecules as
relaxation of many degrees of freedom is involved. We show how a two
dimensional treatment of the involved energy hypersurface reveals universal
maximum and minimum curves which the barriers can be obtained. The rates
obtained are in very good agreement to experiment for mechanochromic
spiropyranes [1] (molecules that change color under the influence of force).
Consideration of the co-monomers and atomic force microscopy tip as effective
strings even allows explaining the force/strain curves seen in recent single
polymer experiments quantitatively.
[1] Fabian Kempe, Oliver Brügner, Hannah Buchheit, Sarah N. Momm, Felix
Riehle, Sophie Hameury, Michael Walter and Michael Sommer Angew. Chemie
Int. Ed. 57 (2018) 997-1000
Keywords: Mechanochemistry, polymer, bond breaking
Presenting authors email: Michael.Walter@fmf.uni-freiburg.de