Mechanically-Induced Chemical Changes in Polymeric Materials

Abstract

Polymeric materials exhibit an extraordinary range of mechanical responses (Figure 1a), which depend on the chemical and physical structure of the polymer chains. 3 Polymers are broadly categorized as thermoplastic, thermoset, or elastomer. Thermoplastic polymers consist of linear or branched chains and can be amorphous or semicrystalline. The mechanical response of thermoplastic polymers is highly influenced by the molecular mass, chain entanglements, chain alignment, and degree of crystallinity. Thermosetting polymers consist of highly cross-linked three-dimensional networks. The mechanical properties of these amorphous polymers depend on the molecular mass and the cross-link density. Elastomers (e.g., rubber) are highly deformable elastic networks that are lightly cross-linked by chemical or physical junctions. Mary M. Caruso (center) was born and raised in Tampa, FL. She received a B.S. degree in Chemistry from Elon University (Elon, NC) in 2006, where she worked under the direction of Prof. Karl D. Sienerth. Her research included the synthesis and electrochemical characterization of a novel palladium complex. She is currently pursuing her Ph.D. in Organic Chemistry at the University of Illinois at Urbana-Champaign under the guidance of Prof. Jeffrey S. Moore and Prof. Scott R. White. Her research interests include the development of new catalyst-free self-healing polymers, microencapsulation, and mechanical testing of bulk polymers. Douglas A. Davis (second from left) was born in Martin, TN. In 2004, he received his B.S. degree in Chemistry from the University of Tennessee, Knoxville, where he worked on surface enhanced Raman spectroscopy (SERS) in an electrospray plume with Professors Charles Feigerle and Kelsey Cook. He joined Prof. Jeffrey Moore's group at the University of Illinois, Urbana-Champaign in 2005 to pursue his Ph.D. in Organic Chemistry. His current research interests include designing and synthesizing mechanophores, which can be induced to undergo chemical reactions with mechanical force. Qilong Shen (third from left) was born in 1974 in Zhejiang Province, China. He received his B.S. degree in Chemistry (1996) from Nanjing University, China, and his M.S. in Chemistry (1999) from Shanghai Institute of Organic Chemistry, the Chinese Science Academy, China, under the supervision of Prof. Long Lu. After a two-year stay at the University of Massachusetts at Dartmouth with Prof. Gerald B. Hammond, he moved to Yale University, where he received his Ph.D. under the guidance of Prof. John F. Hartwig in 2007. He is currently a postdoctoral researcher with Prof. Jeffrey S. Moore at University of Illinois at Urbana-Champaign. His research interests include the discovery, development, and understanding of new transition metal-catalyzed reactions, and the mechanochemistry of polymers.

Chemo-responsive, self-oscillating gels that undergo biomimetic communication

“…Research on synthetic auto-chemotaxing particles is still in its infancy, but recent advances 2,3 point to promising efforts in the creation of mechanically compliant materials that appear to communicate and effectively collaborate. Separate advances in automated responses for self-healing polymeric structures 31,32 and actuating structures 33 have achieved impressive macroscopic motion with nonfunctional polymers, which may eventually be augmented by use of functional, autochemotactic materials. Thus, these advances in responsive gels can pave the way for the design of the next generation of responsive, interactive ''soft robots.''…”

Mechanochemistry in Polymers with Supramolecular Mechanophores

“…Dose-dependent and reversible metal-ligand dissociation occurs upon exposure to ultrasound in solution (Figure 23b, 24a). The absence of ultrasound-induced dissociation of a low-molecular weight model complex and in-depth studies of temperature effects confirm that the dissociation is indeed the result of mechanical activation (for extensive review on sonochemical activation please refer to [11,88]). The influence of the strength of the metal-ligand interactions on the mechanically induced dissociation was also explored.…”

Interplay Between Mechanochemistry and Sonochemistry

“…Mechanical energy can be harnessed in multiple chemical transformations, such as mechanochromism, analyte detection and self-healing. The basic strategy relies upon the concept of the mechanophore; small structural units embedded into long chain polymers which undergo site-selective scission [6][7][8]12]. Although numerous solid-state and solution methods can be used to activate polymers [11], sonication holds the unique ability of providing shear forces and strain in solution by virtue of the mechanical events associated with cavitational collapse.…”

“…This chapter aims to describe the mechanical bias of cavitational effects and how they are related to conventional mechanochemistry and force-induced physical fields in general. This subject has been well documented over the last decade [5][6][7][8][9], and particular attention has been paid to scenarios such as mechanically responsive polymers [10][11][12], micro-and nano-structured materials [13][14][15], and sonocrystallization [16], which are all expected to have a major impact on the fabrication of novel and smart materials as well as the pharmaceutical industry. Although we shall briefly mention these past achievements, our goal is to focus on the aspects of sono-mechanochemistry that have been overlooked in recent thematic issues.…”