Donor-Acceptor Stenhouse Adducts as Intrinsically Photoswitchable Dynamic Covalent Bonds

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Chemistry

Background:

• Dynamic covalent chemistry (DCC) and photoswitches offer light-controlled material properties.
• Current two-component systems face synthetic and compatibility challenges.

Purpose of the Study:

• To develop a single-component strategy for photoswitchable dynamic covalent bonds.
• To create light-tunable covalent adaptable networks (CANs).

Main Methods:

• Utilized donor-acceptor Stenhouse adducts (DASAs) as both photoswitches and dynamic covalent bonds.
• Investigated DASA isomerization and amine donor exchange pathways (dissociation, transamination).
• Incorporated DASAs into PDMS-based networks to form CANs.

Main Results:

• DASAs exhibit light-induced "open" to "closed" isomerization and heat-induced reverse isomerization.
• Open DASA isomers undergo dynamic covalent exchange, which can be arrested by light.
• PDMS networks cross-linked with DASAs displayed light-tunable viscoelastic behavior.
• Identified degradation pathways limiting long-term reversibility under heating.

Conclusions:

• DASA exchange provides a synthetically accessible platform for photocontrolled soft materials.
• DASAs represent a new class of intrinsically photoswitchable dynamic covalent bonds.
• This work paves the way for stimuli-gated dynamic bonds combining reactivity and responsiveness.