NIR-Sensitized Photopolymerization with Iodonium Salts Bearing Weak Coordinating Anions

Abstract

Photoinitiated Polymerization of TPGDA was initiated with a NIR LED emitting at 790 nm using a redox based photoinitiator system comprising a cyanine as photosensitizer and a diaryl iodonium salt.

Comparison between NIR and UV-Sensitized Radical and Cationic Reactivity of Iodonium Salts Comprising Anions with Different Coordination Behavior

“…2a serves in this study as reference. Comparison of 2a, 2d and 2e, which possess the same cation, shows a relatively good reactivity in comparison with previous results [8,19,20]. In this series, the new salt 2e exhibits the best reactivity.…”

“…This quantifies the reactivity by evaluation of the maximum of the polymerization rate R p max , the time to reach R p max (t max ) and the limiting conversion x ∞ . The latter was obtained by integration of the rate of polymerization (R p ) with respect to the time and division of the maximal available reaction heat for the system investigated [8,19,20]. Figure 2 depicts the results obtained for one representative system.…”

“…In this series, the new salt 2e exhibits the best reactivity. This also does not correlate with conductivity ( as previously reported [19,20]. This quantity was assumed to be a quantity describing dissociation of the salt in the monomer that significantly influences the reactivity [19,20].…”

“…It exhibited in some cases a giant solubility in many monomers while the reactivity in NIR-photopolymers was remarkable [8,19] --anion as counter ion. Thus, such methides would form an interesting alternative compared to imides since they should exhibit according to their structure a less nucleophilicity [8,19,20].…”

Nahinfrarot‐sensibilisierte photoinduzierte ATRP mit einer Kupfer(II)‐Katalysatorkonzentration im ppm‐Bereich

“…[10] Ein anderes wichtiges Thema bei Photopolymerisationsverfahren ist die Entwicklung neuer Initiatorsysteme,d ie Licht bei deutlich grçßeren Wellenlängen absorbieren, insbesondere im Nahinfrarot(NIR)-Bereich, wodurch Nebenreaktionen wie die Selbstinitiierung von Monomeren und der Abbau von bereits gebildeten Polymeren verringert werden. [11a, 12] Die Verwendung solcher Systeme ermçglicht es,U V-absorbierende Materialien in Beschichtungen einzuarbeiten [13] und als Flüssigkeit in Flüssiglacken [13,14] oder in fester Form bei Pulverlacken erfolgreich zu applizieren. Dazu kçnnen räumlich modulierte Diodenlaser, die bei 830 nm emittieren, verwendet werden.…”