NIR induced photopolymerization of acrylate-based composite containing upconversion particles as an internal miniaturized UV sources

Upconversion‐Nanoparticle‐Assisted Radical Polymerization at λ=974 nm and the Generation of Acidic Cations

“…Laser exposure resulted in formation of an insoluble crosslinked material (insoluble in common solvents). This result is in agreement with literature results where crosslinking was reported by using similar UCNPs stabilized with citric acid but amine‐based systems were applied in combination either with CQ or benzophenone to initiate crosslinking of multifunctional monomers . More of interest are crosslinkable compositions containing functional additives because this will also give access to new materials in combination with 3D‐printing applications .…”

“…The deeper penetration of NIR light into biological samples and the possibility to excite in a spectral region where functional additives do not significantly attenuate excitation intensity can be the main benefit of this technique ,. Recently, UCNPs were employed for deep‐cure photopolymerisation to generate visible light for excitation of a radical initiator, specifically either titanocene or a system composed of camphorquinone (CQ) and an amine . The use of UCNPs to generate UV initiator systems based on benzophenone (BP) also resulted in larger curing thicknesses.…”

“…Upconversion nanoparticles( UCNPs) sensitised photolytic cleavage of the blue/UV photoinitiator bis (4-methoxybenzoyl) diethylg ermanium (1). 1 initiated radical photopolymerisation in combination with NaYF 4 :TmYb@NaYF 4 UCNPs.Al = 974 nm near-infrared (NIR) laser served as the excitation source to generate blue andU Vl ight. In addition, am etal-free photo-ATRP system (ATRP = atom transfer radicalp olymerisation), composed of iso-propyl thioxanthone (ITX), N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) and a-bromo(iso-butyl) ethylester (a-BrBuEt)w as used instead of 1.T his resulted in a significant smallerp olydispersity compared to the UCNP/1 system.Control of polymerization was successfully demonstrated by meanso fachain extension experiment showing control of chain termination.F or the first time, we demonstrated photolytic formation of acidic cations in such NIR UCNP systems composed of an ITX/iodonium photoinitiator for the sensitized generation of acidic cations.I na ddition, 1 also resultedi n crosslinking of 1,6-hexanediol diacrylate (HDDA) in combination with UCNPs and NIR laser excitation.…”

“…This result is in agreement with literature results where crosslinking was reported by using similar UCNPs stabilized with citric acid but aminebased systemsw ere appliedi nc ombination either with CQ or benzophenone to initiate crosslinking of multifunctional monomers. [4] More of interest are crosslinkable compositions containing functional additives because this will also give access to new materials in combinationw ith 3D-printing applications. [5] This can be, for example, aU Vf ilter material to protect ac rosslinked materialw hichi se xposed for al ong time to sunlight.…”

Efficient photopolymerization of thick pigmented systems using upconversion nanoparticles‐assisted photochemistry

“…Photocurable systems containing pigments and functional fillers are essential for traditional applications such as printing inks, and advanced applications such as color photoresist and 3D printing . However, as compared to the clear system in which the incident light is primarily absorbed by the photoinitiator, the added pigments or colored fillers in resins absorb, reflect, and scatter the light leading to a reduction in the polymerization rate and the final conversion . In a dark system, the penetrating ability of light into the resin and the rate and amount of reactive species generated is further reduced.…”