Wavelength-Dependent Dynamic Behavior in Thiol-Ene Networks Based on Disulfide Exchange

Area of Science:

• Polymer Chemistry
• Materials Science
• Photochemistry

Background:

• Dynamic polymer networks offer controlled bond exchange, but tailorable systems are limited.
• Latent catalysts are established for controlling reactions in dynamic polymer networks.
• Developing inherently tailorable dynamic polymer systems remains a challenge.

Purpose of the Study:

• To develop a tailorable thiol-ene polymer network with light-responsive dynamic properties.
• To demonstrate control over polymer network dynamics using different light wavelengths.
• To create a catalyst-free system for dynamic bond exchange in photopolymers.

Main Methods:

• Synthesis of allyl-bearing disulfides responsive to specific UV light wavelengths.
• Photocuring of thiol-ene resins using visible (450 nm) and UV (365 nm) light.
• Characterization of polymer networks using UV-vis spectroscopy, EPR measurements, and stress relaxation tests.

Main Results:

• Photopolymers cured at 450 nm exhibit dynamic disulfide bonds, showing significant stress relaxation (63% in 112 s at 160 °C).
• Photopolymers cured at 365 nm undergo disulfide scission, forming stable monosulfidic links with minimal stress relaxation.
• The dynamic properties of the thiol-ene network are successfully altered solely by the wavelength of light used during curing.

Conclusions:

• Light color can precisely control the dynamic properties of thiol-ene polymer networks.
• This approach offers a catalyst-free method for creating tunable dynamic polymer materials.
• The developed system demonstrates significant potential for advanced materials with on-demand property modulation.