NIR-Sensitized Cationic and Hybrid Radical/Cationic Polymerization and Crosslinking.

Area of Science:

• Polymer Chemistry
• Photochemistry
• Materials Science

Background:

• Cationic polymerization is a vital process for creating various polymers.
• Developing efficient photoinitiator systems, especially those activated by near-infrared (NIR) light, is crucial for advanced material processing.
• Understanding the role of counterions in photoinitiated polymerization is essential for controlling reactivity and network formation.

Purpose of the Study:

• To investigate the efficiency of NIR-sensitized cationic polymerization using a heptacyanine sensitizer and iodonium salt coinitiator.
• To evaluate the influence of different counterions on polymerization kinetics and outcomes.
• To explore the formation of interpenetrating polymer networks (IPNs) under NIR irradiation.

Main Methods:

• NIR-sensitized cationic polymerization of epoxides, vinyl ether, and oxetane.
• Utilized a heptacyanine sensitizer and iodonium salt coinitiator.
• Investigated a series of fluorinated phosphate, aluminate, and methide anions.
• Employed Density Functional Theory (DFT) calculations to analyze anion electrostatic potential.
• Examined IPN formation using trimethylpropane triacrylate and epoxides under NIR and UV-LED initiation.

Main Results:

• NIR-sensitized cationic polymerization demonstrated good efficiency across various monomers, with vinyl ether showing the highest reactivity.
• The choice of anion significantly impacted polymerization efficiency, with specific fluorinated aluminates and phosphates showing promising results.
• DFT calculations indicated a correlation between anion electrostatic potential and reactivity.
• Interpenetrating polymer networks (IPNs) were successfully formed using NIR initiation with specific anions, but not with UV-LED initiation under similar conditions.

Conclusions:

• NIR-sensitized cationic polymerization is a viable and efficient method for polymer synthesis.
• Counterion selection plays a critical role in controlling the efficiency and outcomes of NIR-initiated polymerization.
• The ability to form IPNs under NIR light opens possibilities for advanced material fabrication with spatiotemporal control.