SPECTROSCOPY, IMAGING, OTHER TECHNIQUES |
Sacrificial Bonds and Hidden Length: Unraveling Molecular Mesostructures in Tough Materials
Georg Ernest Fantner 1*, Emin Oroudjev 1, Georg Schitter 1, Laura S Golde 1, Philipp Johannes Thurner 1, Marquesa Maliglig Finch 1, Patricia Thurner 1, Thomas Gutsmann 2, Daniel E Morse 1, Helen Hansma 1 and Paul K Hansma 1
1 University of California Santa Barbara
2 Research Center Borstel
* To whom correspondence should be addressed. E-mail: fantner{at}physics.ucsb.edu.
Submitted on June 23, 2005
Revised on October 3, 2005
Accepted on 28 October 2005
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Abstract |
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Sacrificial bonds and hidden length in structural molecules and composites have been found to greatly increase the fracture toughness of biomaterials (1) by providing a reversible, molecular-scale energy-dissipation mechanism. This mechanism relies on the energy, of order 100 eV, needed to reduce entropy and increase enthalpy as molecular segments are stretched after being released by the breaking of weak bonds, called sacrificial bonds(2). This energy is relatively large compared to the energy needed to break the polymer backbone, of order a few eV. In many biological cases, the breaking of sacrificial bonds has been found to be reversible, thereby additionally providing a "self-healing" property to the material(1,3). Due to the nanoscopic nature of this mechanism, single molecule force spectroscopy using an atomic force microscope (4-6) has been a useful tool to investigate this mechanism. Especially when investigating natural molecular constructs, force vs. distance curves quickly become very complicated (7). In this work we propose various types of sacrificial bonds, their combination and how they appear in single molecule force spectroscopy measurements. We find that by close analysis of the force spectroscopy curves, additional information can be obtained about the molecules and their bonds to the native constructs.
Key Words:
composites, energy dissipation, pulling, single molecule force spectroscopy, worm like chain
