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Force-rate characterization of two spiropyran-based molecular force probes
Gregory R Gossweiler1, Tatiana B Kouznetsova1, Stephen L Craig1
1Department of Chemistry, Duke University, Durham, North Carolina 27708, United States.
Journal of the American Chemical Society
|April 29, 2015
Summary
Mechanically induced spiropyran ring-opening requires low forces (~240 pN), enabling polymer stress imaging. Force magnitude and regiochemistry influence this mechanochemical reaction, revealing insights into polymer dynamics.
Area of Science:
- Polymer Science
- Mechanochemistry
- Spectroscopy
Background:
- Spiropyran to merocyanine conversion images polymer stress/strain.
- Quantifying activation forces for this reaction is crucial.
- Previous mechanophores required higher forces.
Purpose of the Study:
- Quantify the forces needed for spiropyran ring-opening.
- Investigate the influence of regiochemistry on mechanochemical coupling.
- Characterize the force-dependent kinetics of spiropyran isomers.
Main Methods:
- Single molecule force spectroscopy (SMFS).
- Studied two spiropyran isomers.
- Analyzed ring-opening kinetics under varying forces.
Main Results:
- Ring opening on millisecond timescales requires ~240 pN forces.
- This threshold is lower than for covalent mechanophores.
- Regiochemical effects were characterized, with force reversing isomer-specific rates.
Conclusions:
- Spiropyran mechanochemistry offers a sensitive method for polymer stress mapping.
- Low activation forces and high force sensitivity enable detailed mechanical analysis.
- Understanding regiochemical effects is key for designing effective mechanophores.
