Acylstannane: Spaltbare und hochreaktive Photoinitiatoren für radikalische Photopolymerisationen bei Wellenlängen über 500 nm mit exzellentem Photobleaching

Abstract

In der vorliegenden Arbeit wird ein neuer Acylstannan-basierter Photoinitiator (PI) präsentiert. Im Vergleich mit Acylgerman-Initiatoren zeigt Tetrakis(2,4,6-trimethylbenzoyl)stannan (1)h erausragende Eigenschaften. Vora llem zeigt dieser Initiator Absorption bis 550 nm, was hçhere Eindringtiefen in gefüllten Systemen ermçglicht. Zusätzlich zeigt Acylstannan 1 extrem hohe Aktivitätb ei der Initiierung von (Meth)acrylaten sowies ehr schnelles Photobleaching.I mG egensatz zu vielen anderen Zinnorganylen zeigt 1 außerdem überraschend niedrige Zytotoxizität. Schema 1. Synthese von Tetrakis(2,4,6-trimethylbenzoyl)stannan (1).

Synthesis and Photochemical Investigation of Tetraacylgermanes

“…The rate of decomposition (R d ) was calculated according to literature [Equation ( 1 )]. [10,24] The value A 0 was taken from the absorbance maximum before the measurement was started, while A 1 was the value corresponding to the sample taken after 60 s (t 1 ) of irradiation and A 2 equals the absorbance of the sample taken after 180 s (t 2 ). All A values were measured at the respective λ max .…”

“…In order to determine the quantum yield of decomposition (Φ d ) for the measurements conducted at 385 nm, the literature [20] known Φ d 385 nm of Ivocerin® (0.83) was used to determine the photon flux (I 0 ) in the system, by transforming Equation ( 2): [10]…”

“…[8] The penetration depth of light into the suspension containing the polymerizable formulation with ceramic particles is of utmost importance, as it is crucial for generating sufficient layer thickness. [9] Mitterbauer et al [10] proved that the depth of cure (C d ) can be enhanced by utilizing PIs with a higher absorption in the tail out region of the absorption spectrum compared to Ivocerin®. This allows the utilization of red-shifted LEDs for the printing process because longer wavelengths lead to a higher penetration depth of light.…”

“…[14] Another way to synthesize PIs with a red shifted absorption was the preparation of acylstannanes. [10] Due to the central tin atom, the nπ*-transition occurs at even higher wavelengths. A special form of tin-based PIs are R 6 Sn 2 species [15] that are initiating as R 3 Sn radicals.…”