NIR‐Sensitized Cationic and Hybrid Radical/Cationic Polymerization and Crosslinking
Yulian Pang, Atsushi Shiraishi, Dietmar Keil, Sergey A. Popov, Veronika Strehmel, Hongjun Jiao, Jochen S. Gutmann, Yingquan Zou, Bernd Strehmel
Abstract
Abstract NIR‐sensitized cationic polymerization proceeded with good efficiency, as was demonstrated with epoxides, vinyl ether, and oxetane. A heptacyanine functioned as sensitizer while iodonium salt served as coinitiator. The anion adopts a special function in a series selected from fluorinated phosphates ( a : [PF 6 ] − , b : [PF 3 (C 2 F 5 ) 3 ] − , c : [PF 3 ( n ‐C 4 F 9 ) 3 ] − ), aluminates ( d : [Al(O‐ t ‐C 4 F 9 ) 4 ] − , e : [Al(O(C 3 F 6 )CH 3 ) 4 ] − ), and methide [C(O‐SO 2 CF 3 ) 3 ] − ( f ). Vinyl ether showed the best cationic polymerization efficiency followed by oxetanes and oxiranes. DFT calculations provided a rough pattern regarding the electrostatic potential of each anion where d showed a better reactivity than e and b . Formation of interpenetrating polymer networks (IPNs) using trimethylpropane triacrylate and epoxides proceeded in the case of NIR‐sensitized polymerization where anion d served as counter ion in the initiator system. No IPN was formed by UV‐LED initiation using the same monomers but thioxanthone/iodonium salt as photoinitiator. Exposure was carried out with new NIR‐LED devices emitting at either 805 or 870 nm.