Mechanically Activated Rupture Of Single Covalent Bonds: Evidence Of Force-Induced Bond Hydrolysis.pdf

The article, "Mechanically Activated Rupture of Single Covalent Bonds: Evidence of Force-Induced Bond Hydrolysis," published in Phys. Chem. Chem. Phys. (2011), investigates the rupture of covalent bonds under mechanical stress using temperature-dependent single molecule force spectroscopy. Researchers from Munich University of Applied Sciences, Kiel University, and CeNS Munich analyzed the bond rupture kinetics of carboxymethylated amylose (CMA) polymers attached to an AFM cantilever.

Key Findings:

1. Reduced Dissociation Energy and Arrhenius Pre-factors: The study reveals a significantly smaller dissociation energy (35.5 kJ mol⁻¹) and Arrhenius pre-factors (9.0 × 10² s⁻¹ to 3.6 × 10³ s⁻¹) compared to expected values for homolytic bond scission, suggesting mechanically activated hydrolysis of covalent bonds.

2. Competing Rupture Mechanisms: Scattering, slope, and curvature of the data plots indicate two competing rupture mechanisms: one involving the carboxylic acid amide bond and another potentially related to the siloxane bond in the amino-silane surface linker.

3. Arrhenius Kinetics Model: By varying temperature and using a maximum likelihood method for data fitting, researchers successfully extracted kinetic parameters describing the unbinding kinetics of the system.

4. Comparison with Thermodynamic and Spectroscopic Data: The obtained results are compared to thermodynamic and spectroscopic data, as well as theoretical modeling, supporting the hypothesis of mechanically activated hydrolysis as a possible rupture mechanism.

Significance:

This research provides valuable insights into the mechanical stability of covalent chemical bonds, contributing to our understanding of material failure and the control of reactions through force in synthetic and natural product chemistry.