Wavelength-Selective Sequential Polymer Network Formation Controlled with a Two-Color Responsive Initiation System.

Area of Science:

• Polymer Chemistry
• Materials Science
• Photochemistry

Background:

• Sequential polymerization offers control over material properties.
• Previous methods lacked precise control over distinct polymerization stages.

Purpose of the Study:

• To develop a wavelength-selective polymerization process.
• To enable sequential thiol-Michael and radical polymerization using visible and UV light.
• To demonstrate tunable material properties through controlled dual-cure photopolymerization.

Main Methods:

• Utilized a photobase generator (NPPOC-TMG) and a photo-radical initiator (Irgacure 2959).
• Employed visible light (400-500 nm) for anion-mediated polymerization and UV light (365 nm) for radical polymerization.
• Monitored polymerization using FT-IR and rheological tests; characterized mechanical properties via dynamic mechanical analysis (DMA).

Main Results:

• Achieved wavelength-selective generation of bases and radicals for sequential polymerization.
• Produced a soft intermediate polymer under visible light, followed by a rigid, cross-linked material under UV light.
• Demonstrated successful application in thiol-Michael and thiol-ene hybrid polymerization systems.

Conclusions:

• The developed dual-wavelength system provides precise control over sequential polymerization.
• This method allows for tunable material properties, transitioning from flexible to rigid states.
• The chosen initiator pair shows significant potential for regulating various coupled anion and radical hybrid polymerizations.