Novel Photoinitiator for Modern Technology

Mechanistic Investigations on a Diynone Type Photoinitiator

“…Another disadvantage of DPE and DTE is their low triplet energy (E T(DPE) % 247 kJ mol À1 ), which enables them to quench the triplet states of most PIs. The application of the acrylic ester t-BAM as trapping agent for radicals has been described by Dietliker et al [8] Complex synthesis [12][13][14] has avoided widespread application of this excellent nonpolymerizable model compound for acrylate based monomers.…”

“…[4] Alternatively, the radicals could be quenched with stable radicals or non-polymerizable double bond to create stable products, which could be analyzed with analytical routine methods like NMR, IR, or MS. Different quenchers such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), [5] 1,1-diphenylethene (DPE), 1,1-di(p-tolyl)ethene (DTE), [6,7] and methyl 3,3-dimethyl-2-methylenebutanoate t-BAM [8,9] (Figure 1) have been described. TEMPO, a commercially available stable radical, reacts efficiently with carbonyl radicals originating from, e.g., cleavable hydroxy-or aminoalkylphenones.…”

Copolymeric systems bearing side‐chain thioxanthone and α‐aminoacetophenone moieties as photoinitiators for ultraviolet‐curable pigmented coatings

“…Indeed, poly (MATX) and poly(MATX-co-BA) show both the and BDMB, reported previously. 9,10 Indeed, the electron withdrawing character of the morpholino above absorption bands. In particular, the structured band related to the n r p* electronic transigroup in the para position to the benzoyl group causes a bathochromic shift of the p r p* transition, usually involved in photoinitiation and photosensitization processes, exhibits in poly(MATX) tion from 250 to over 320 nm, thus completely obscuring the much less intense n r p* transition It is worth noting that in the copolymer samples, in agreement with what was observed for of the ketone group, located in this spectral region.…”

“…In this context, taking into account that 1-methyloxycarbonylthioxanthone) (E T Å 63 kcal/ mole) is able 10 to photosensitize BDMP and Very recently, the polymeric analogues of the BDMB (E T Å 60 kcal/mole) by energy transfer, low-molecular-weight photoinitiators 2-benzyl-2-copolymers, containing in the same macromoledimethylamino-1-(4-morpholinophenyl)propancules, side-chain 1-alkoxycarbonyl-thioxanthone 1-one (BDMP) and 2-benzyl-2-dimethylamino-1-and a-aminoacetophenone moieties derived from (4-morpholinophenyl)butan-1-one (BDMB), 9,10 BMMP and BMMB appeared very promising for i.e., the homopolymers of 1-(4-morpholinopheimproving the photoinitiation activity in the cure nyl) -2 -benzyl -2 -[N -methyl -N -(3 -methacrylof pigmented coatings. Indeed, an increase of the oyloxypropyl)]aminopropan-1-one (BMMP) and photocure efficiency by the above copolymers is of 1-(4-morpholinophenyl)-2-benzyl-2-[N-methexpected, not only through an energy transfer yl-N-(3-methacryloyloxypropyl)]aminobutan-1-mechanism from excited thioxanthone groups to one (BMMB) [poly(BMMP) and poly(BMMB), the adjacent ground state a-morpholinoacetopherespectively] were prepared and successfully apnone moieties, but also through a photoreduction plied to the UV cure of a standard acrylic formulaprocess involving the thioxanthone moieties in the tion, under irradiation conditions simulating a triplet state and the tertiary amino groups in bTiO 2 -pigmented coating (l irr ú 380 nm).…”

Copolymeric systems with pendant thioxanthone and α‐morpholinoacetophenone moieties as photosensitizing and photoinitiating agents for UV‐curable pigmented coatings

“…Actually, the most favorable photosensitizer-photoinitiator combination is obtained when l-alkyloxycarbonylthioxanthones or 2-isopropylthioxanthone is jointed to a-aminoacetophenones, and particularly to l-[4-(methylthio)phenyl~-2-methyl-2-morpholino-propan-1-one (MMMP), giving rise to a remarkable synergistic effect in the UV curing of white pigmented lacquers and blue silk screen inks. [20][21][22][23][24] Indeed, the triplet state energy level of the abovementioned thioxanthone derivatives (63 and 61.4 kcal mol-', respectively) is slightly higher than that of MMMP (61 kcal mol-l). In this context, it appeared very interesting to prepare copolymers bearing side-chain 1 -alkyloxycarbonylthioxanthone and 1-(4-alkylthiophenyl) -2-methyl-2-morpholinopropan-1-one moieties, as the forced close vicinity of the sensibilizing and photoinitiating species would not only favor the excitation energy transfer and hence increase the UV curing rate of Ti02-pigmented coatings, but also improve their performances in terms of nonyellowing and low-odor properties, due to the macromolecular nature of the system.…”