A backbone lever-arm effect enhances polymer mechanochemistry.
Mechanical forces along a polymer backbone can be used to bring about remarkable reactivity in embedded mechanically active functional groups, but little attention has been paid to how a given polymer backbone delivers that force to the reactant. Here, single-molecule force spectroscopy was used to directly quantify and compare the forces associated with the ring opening of gem-dibromo and gem-dichlorocyclopropanes affixed along the backbone of cis-polynorbornene and cis-polybutadiene. The critical force for isomerization drops by about one-third in the polynorbornene scaffold relative to polybutadiene. The root of the effect lies in more efficient chemomechanical coupling through the polynorbornene backbone, which acts as a phenomenological lever with greater mechanical advantage than polybutadiene. The experimental results are supported computationally and provide the foundation for a new strategy by which to engineer mechanochemical reactivity.
Department of Chemistry, Duke University, Durham, North Carolina 27708, USA.
Hope M
HM
Klukovich
Tatiana B
TB
Kouznetsova
Zachary S
ZS
Kean
Jeremy M
JM
Lenhardt
Stephen L
SL
Craig
D002070:Butadienes / Q000737:chemistry*; D003198:Computer Simulation; D020724:Elastomers / Q000737:chemistry*; D019563:Mechanics; D015394:Molecular Structure; D010969:Plastics / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods
D002070:Butadienes; D020724:Elastomers; D010969:Plastics; C071464:polynorbornen; C028834:polybutadiene