Accession Number : ADA606143


Title :   Mechanophores for Self-Healing Applications


Descriptive Note : Book chapter


Corporate Author : ILLINOIS UNIV AT URBANA BOARD OF TRUSTEES


Personal Author(s) : Diesendruck, Charles E ; Moore, Jeffrey S


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a606143.pdf


Report Date : 09 Sep 2013


Pagination or Media Count : 24


Abstract : The transformation of chemical energy into mechanical energy is elementary in our lives, not only moving cars and airplanes, but pumping blood in our bodies and moving our eyeballs as we read these lines. The reverse action, defined as mechanochemistry, is to make chemical transformations using mechanical force, and finding simple examples may be challenging for people unfamiliar with the subject. An important step to ease the study of mechanochemistry of polymers was the development of mechanical stressing in solution, where chemical changes are distributed homogeneously through the chains. Moreover, classical analytical chemistry methods to analyze the chemical changes, such as spectrometers, laser light scattering and others could be used, giving the possibility to study molecular weight change and kinetics of the mechanochemical reactions. This important breakthrough came early and was achieved through the use of flow fields and ultra-sound cavitation that caused high shear stress on the chains through flow induced elongation. A key discovery that came from the study in solution was the observation that certain bonds cleave more easily than others. If one of these bonds is present in the main chain, close to its center (Figure 8.1), it can be selectively cleaved. This originated the concept of mechanophores -- bonds or chemical functionalities that are especially susceptible to undergoing a chemical change caused by mechanical stress. Mechanophores, when placed into a polymeric molecule where the mechanical force is highest, selectively undergo a chemical reaction. In this chapter we will describe how polymeric materials deal with mechanical stress, methods to mechanically stress materials in a controlled manner to study the chemical changes, and the development of mechanophores that direct mechanical energy to molecular constituents to produce positive effects on the material, such as self-healing.


Descriptors :   *POLYMERS , CHEMICAL BONDS , MECHANICAL ENERGY , TENSILE STRESS


Subject Categories : Physical Chemistry
      Polymer Chemistry
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE