Switching "on" and "off" the adhesion in stimuli-responsive elastomers

Area of Science:

• Materials Science
• Polymer Chemistry
• Adhesion Science

Background:

• Developing stimuli-responsive materials for tunable adhesion is crucial for advanced applications.
• Reversible covalent chemistry offers a pathway to create dynamic polymer networks.

Purpose of the Study:

• To prepare dry adhesives with switchable bonding properties using reversible anthracene cycloaddition.
• To investigate the photo- and thermal-induced crosslinking and cleavage dynamics.
• To characterize the network properties and adhesion performance over multiple cycles.

Main Methods:

• One-pot synthesis of photo-responsive hydrogenated carboxylated nitrile butadiene rubber with pendant anthracene groups.
• UV-vis spectroscopy for monitoring photodimerization and cleavage kinetics in thin films.
• Low-field NMR spectroscopy and dynamic mechanical analysis for characterizing bulk properties.
• Adhesion force mapping for assessing spatial control.

Main Results:

• Successful formation of 3D networks via anthracene photodimerization upon UV exposure.
• Controlled network cleavage achieved through deep UV (254 nm) or thermal treatment (70 °C).
• Demonstrated reversible switching of adhesion properties with significant recovery (75-80%) after dissociation.
• Spatial control of adhesion achieved through photo-patterning.

Conclusions:

• The reversible [4πs+4πs] cycloaddition of anthracenes enables the creation of dry adhesives with switchable on/off adhesion.
• Both photo- and thermal-induced dissociation provide effective routes for debonding.
• The developed materials exhibit robust reversibility and tunable adhesion for potential applications.