From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

• Published in: Macromolecular rapid communications. Vol. 42; no. 1; pp. e2000573 - n/a
• Main Authors: Traeger, Hanna, Kiebala, Derek J., Weder, Christoph, Schrettl, Stephen
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.01.2021
• Subjects: Chemical bonds; Cleavage; color change; Covalence; Covalent bonds; Deformation; Deformation effects; luminescence; mechanochromic polymers; mechanoresponsive polymers; noncovalent interactions; Optical properties; polymer materials; Polymers; stimuli responsive polymers; Stresses; luminescence; mechanoresponsive polymers; color change; mechanochromic polymers; noncovalent interactions; polymer materials; stimuli responsive polymers
• ISSN: 1022-1336; 1521-3927; 1521-3927
• DOI: 10.1002/marc.202000573

The development of mechanophores as building blocks that serve as predefined weak linkages has enabled the creation of mechanoresponsive and mechanochromic polymer materials, which are interesting for a range of applications including the study of biological specimens or advanced security features. In typical mechanophores, covalent bonds are broken when polymers that contain these chemical motifs are exposed to mechanical forces, and changes of the optical properties upon bond scission can be harnessed as a signal that enables the detection of applied mechanical stresses and strains. Similar chromic effects upon mechanical deformation of polymers can also be achieved without relying on the scission of covalent bonds. The dissociation of motifs that feature directional noncovalent interactions, the disruption of aggregated molecules, and conformational changes in molecules or polymers constitute an attractive element for the design of mechanoresponsive and mechanochromic materials. In this article, it is reviewed how such alterations of molecules and polymers can be exploited for the development of mechanochromic materials that signal deformation without breaking covalent bonds. Recent illustrative examples are highlighted that showcase how the use of such mechanoresponsive motifs enables the visual mapping of stresses and damage in a reversible and highly sensitive manner. The exposure of polymer materials to mechanical stresses can deteriorate their properties. Mechanochromic polymers respond to applied stresses through a signal, which can be used to monitor deformation or assess damage. In this article, an overview is provided of the responses that can be obtained when mechanoresponsive motifs that respond without covalent bond cleavage are used to prepare mechanochromic materials.