Application of osmium metal complex as electron transfer photosensitizer in full-band photopolymerization

Abstract

The invention belongs to the technical field of photocuring materials, and particularly relates to a photoinitiator composition taking an osmium metal complex as an electron transfer photosensitizer and application of the photoinitiator composition to induction of free radical, cation and hybrid polymerization in a full wave band. The invention provides a full-wave band response type photoinitiator based on osmium metal complexes (such as Os-diphen and Os-phen). The full-wave band response type photoinitiator is composed of an osmium complex photosensitizer and iodonium salt (or iodonium salt + N-vinyl carbazole). And full-wave band light response from ultraviolet to near infrared (365-690 nm) is realized. An efficient photo-induced electron transfer (PET) mechanism is established, and free radical and cation polymerization can be initiated at the same time. Under the irradiation of 690 nm red light, the double bond conversion rate of the system to an acrylate monomer can reach 51%, and deep curing of 23 cm is realized; the sunlight-driven polymerization reaction is successfully realized, and the application potential in the fields of deep curing, 3D printing, solar photopolymerization and the like is shown.

Description

Technical Field

[0001] This invention belongs to the field of photocurable materials technology, specifically relating to a photoinitiator composition of osmium metal complex as an electron transfer photosensitizer and its application in inducing free radical, cationic and hybrid polymerization across the entire wavelength range. Background Technology

[0002] Photopolymerization technology, with its advantages of high efficiency, environmental friendliness, and precise curing with regional selectivity, has become a core technology in fields such as microelectronics lithography, advanced manufacturing, and biomedicine. However, most existing photoinitiation systems rely on ultraviolet light, which leads to two major bottlenecks: first, ultraviolet light has high photon energy, which easily induces photodegradation of materials, and also suffers from strong Rayleigh scattering and limited penetration depth; second, the proportion of ultraviolet components in the solar spectrum and common LED light sources is low, resulting in low overall spectral utilization and high energy consumption.

[0003] To address this, researchers have developed photosensitizers based on electron transfer mechanisms to improve the long-wavelength performance of photopolymerization systems. These photosensitizers utilize their superior long-wavelength properties to avoid problems associated with ultraviolet light, improve spectral utilization, and solve issues such as curing depth. In these systems, the photosensitizer absorbs light energy to reach an excited state, and through a photoinduced electron transfer (PET) process with a co-initiator, indirectly generates active free radicals or cationic species capable of initiating monomer polymerization. The photosensitizer itself then returns to its ground state. Photoinitiation systems based on this mechanism require the photosensitizer to have a high molar extinction coefficient within the emission spectral range, redox potential matching with the co-initiator, cyclicity, and a long excited-state lifetime.

[0004] Currently, photosensitizers suitable for this system mainly fall into two categories: organic dyes and metal complexes. Among them, metal complex photosensitizers (such as those based on iron, copper, ruthenium, and iridium) have attracted widespread attention due to their high molar extinction coefficients and long excited-state lifetimes. However, their absorption performance in the red to near-infrared region is generally insufficient, failing to achieve a full-spectrum response and thus failing to meet the requirements of deep curing or solar-driven polymerization. Osmium metal complexes, due to their strong spin-orbit coupling effect, possess long excited-state lifetimes and significant absorption in the red / near-infrared region, and have been applied in photocatalytic and electrocatalytic redox systems and the TTA-UC field (core role: energy conversion).

[0005] Therefore, it is of great significance to develop a new and efficient photoinitiation system to promote the development of photopolymerization technology towards longer wavelengths, higher efficiency, and wider applications. Summary of the Invention

[0006] The purpose of this invention is to overcome the technical shortcomings of existing photopolymerization technologies, such as strong dependence on ultraviolet light, low initiation efficiency in long wavelength regions, and the difficulty of achieving full-band response and deep curing with traditional metal photosensitizers. To address these problems, this application utilizes osmium metal complexes as electron transfer photosensitizers in the field of photopolymerization, combined with an initiator, to achieve full-band initiation polymerization.

[0007] The preparation method of this invention utilizes the unique properties of osmium metal to conduct ligand exchange and anion substitution reactions with different conjugated complexes, resulting in two osmium metal complexes. These two osmium metal complexes exhibit good absorption performance across the entire wavelength range and possess long excited-state lifetimes. Using osmium metal complexes as electron transfer photosensitizers for photocuring enables full-wavelength polymerization, improving spectral utilization, and the long excited-state lifetime also enhances energy utilization efficiency.

[0008] A first aspect of the present invention provides a photoinitiator composition comprising an osmium metal complex and an iodonium salt; wherein the osmium metal complex serves as an electron transfer photosensitizer in a photopolymerization system; Furthermore, the osmium metal complex is one or a combination of compounds shown in formula (I) or formula (II): (I) (II).

[0009] In some embodiments, the photoinitiator composition further includes N-vinylcarbazole.

[0010] In some embodiments, the amount of osmium metal complex added is 0.1 wt% to 1 wt% based on the total mass of polymerizable monomers, and the amount of iodonium salt added is 1 wt% to 3 wt%.

[0011] Furthermore, the selection of the iodonium salt follows the bandgap matching principle, that is, its reduction potential must be compatible with the reducing power of the excited state of the photosensitizer in order to drive an effective electron transfer process; the iodonium salt is preferably a diphenyliodonium salt. A second aspect of the present invention provides a photopolymerization method, wherein the photoinitiator composition can initiate free radical polymerization of monomers under light irradiation with a wavelength of 200-700 nm.

[0012] In some embodiments, the amount of osmium metal complex added is 0.1 wt% to 1 wt%, the amount of iodonium salt added is 1 wt% to 3 wt%, and the amount of N-vinylcarbazole added is 2 wt% to 4 wt%, based on the total mass of polymerizable monomers.

[0013] In some embodiments, the photoinitiator composition can initiate free radical polymerization, cationic polymerization, or hybrid polymerization of monomers under light irradiation with a wavelength of 200-700 nm.

[0014] In some embodiments, the photoinitiation system of the present invention comprises a two-component photopolymerization system of a photosensitizer and an initiator, which achieves curing of free radical monomers under irradiation with light of all wavelengths (ultraviolet, visible, and near-infrared). Further, the response wavelength of the photoinitiation system is 200-700 nm, preferably 365-700 nm.

[0015] In one embodiment, the photosensitizer includes Os-diphen and Os-phen; the initiator is an iodonium salt; and the monomer includes tripropylene glycol diacrylate and trimethylolpropane triacrylate.

[0016] In a preferred embodiment, the amounts of osmium metal complex photosensitizer and iodonium salt added in the photopolymerization system are 0.1~1 wt% and 2 wt%, respectively.

[0017] In some embodiments, the photoinitiation system of the present invention comprises a three-component photopolymerization system consisting of a photosensitizer, an initiator, and a co-initiator, which achieves the curing of free radicals, cationic or hybrid monomers under irradiation with light across the entire wavelength range. The response wavelength of the photoinitiation system is 200-700 nm, preferably 365-700 nm.

[0018] In one embodiment, the photosensitizer includes Os-diphen and Os-phen; the initiator is an iodonium salt; and the co-initiator is N-vinylcarbazole. In a preferred embodiment, the amounts of osmium metal complex photosensitizer, iodonium salt, and co-initiator added to the photopolymerization system are 0.1~1 wt%, 2 wt%, and 3 wt%, respectively.

[0019] Furthermore, the monomers include acrylate monomers, epoxy monomers, and vinyl ether monomers.

[0020] In some embodiments, the acrylate monomer is selected from one or more of tripropylene glycol diacrylate, trimethylolpropane triacrylate, and methyl acrylate; In some embodiments, the epoxy monomer is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate.

[0021] In some embodiments, the ethylene ether monomer is n-butylethylene ether.

[0022] In some embodiments, the monomer is cured to a depth of ≥10 cm under 690 nm light source irradiation; preferably, the curing depth is ≥20 cm, and more preferably, the curing depth is ≥23 cm.

[0023] In some implementations, when a 690 nm light source is used and the monomer is trimethylolpropane triacrylate, the double bond conversion rate is not less than 50%.

[0024] Another aspect of the present invention provides a method for preparing the osmium metal complex, wherein 4,7-diphenyl-1,10-phenanthroline is reduced and ligand exchanged with potassium hexachloroosmium tetroxide, and then subjected to an anion exchange reaction with an aqueous solution of ammonium hexafluorophosphate.

[0025] In some embodiments, the preparation method specifically includes the following steps: Step S1: 4,7-Diphenyl-1,10-phenanthroline, potassium hexachloroosmium tetroxide, ethylene glycol and N-ethylmorpholine are reacted at 220 °C for 10 h. After heating is completed, the reaction solution is allowed to cool to room temperature.

[0026] In step S2, the reaction solution was transferred to an aqueous solution containing ammonium hexafluorophosphate and stirred at room temperature for 1 h. The precipitate in the reaction solution was filtered and washed with water until the filtrate was colorless. The product was dried and dehydrated to obtain a black solid.

[0027] In step S1, the molar ratio of the corresponding complex and potassium hexachloroosmium tetroxide is 1:10 to 10:1.

[0028] In step S2, the molar ratio of the complex, potassium hexachloroosmium tetroxide, and ammonium hexafluorophosphate is 1:10 to 10:1.

[0029] Beneficial effects: (1) The photoinitiating system of the present invention, by combining osmium complexes with iodonium salts, can efficiently initiate free radical polymerization under ultraviolet to near-infrared light irradiation, exhibiting excellent long-wavelength initiation performance for acrylate monomers. The photoinitiating system of the present invention can efficiently initiate polymerization under a full range of light irradiation from 365 nm to 690 nm; (2) The photoinitiation system of the present invention initiates the curing of free radical monomers, cationic monomers, and hybrid monomers across the entire wavelength range by combining osmium complexes with initiators and co-initiators, and exhibits good initiation efficiency. The double bond conversion rate of acrylate monomers (TMPTA) under 690 nm red light can reach 51%; (3) The photoinitiation system of the present invention effectively overcomes the scattering and shielding effects of ultraviolet light; under 690 nm laser irradiation, a curing depth of 23 cm is achieved, providing a creative solution for the processing of thick cross-section materials.

[0030] (4) The polymerization method of the present invention is simpler and more efficient than the traditional TTA-UC process. It successfully solves the problem of poor long-wavelength performance of traditional photoinitiators. By simply compounding the co-initiator NVK, it can flexibly switch between free radical and cationic polymerization modes and has a wide range of applications. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the present application and form part of the specification. They are used together with the embodiments of the present application to explain the application and do not constitute a limitation thereof. In the drawings: Figure 1 The synthetic route of the photosensitizer in Example 1 of this invention is shown below; Figure 2 A is the 1H NMR spectrum of Os-diphen in Example 1 of this invention; B is the 1H NMR spectrum of Os-phen; Figure 3 The UV-Vis absorption spectra of the photosensitizers Os-diphen and Os-phen are shown. Figure 4 A is the steady-state photolysis spectrum of the photosensitizer in Example 3 of the present invention under 690 nm LED irradiation; B is the steady-state photolysis spectrum of the photosensitizer combined with iodonium salt in Example 3 under 690 nm LED irradiation; C is the steady-state photolysis spectrum of the photosensitizer combined with iodonium salt and N-vinylcarbazole in Example 4 under 690 nm LED irradiation. Figure 5 The ESR spectrum of the photosensitizer Os-diphen combined with iodonium salt is shown. Figure 6 A is the electrochemical spectrum of Os-diphen in Example 2 of the present invention; B is the electrochemical spectrum of Os-phen in Example 2 of the present invention; C is the electrochemical spectrum of iodonium salt in Example 2 of the present invention.

[0032] Figure 7 This is a mechanism diagram of the photopolymerization system of the present invention; Figure 8 A shows the real-time infrared curve of TMPTA induced by Os-diphen alone under LED@690 nm illumination; B shows the real-time infrared curve of TMPTA induced by different contents of Os-diphen and iodonium salt under LED@690 nm illumination; C shows the real-time infrared curve of TMPTA induced by different contents of Os-diphen, iodonium salt, and N-vinylcarbazole under LED@690 nm illumination. Figure 9 Real-time infrared curves of TMPTA induced by Os-diphen with iodonium salt and N-ethylenecarbazole under different wavelengths of light.

[0033] Figure 10Real-time infrared curves of EPOX induced by Os-diphen with iodonium salt and N-ethylenecarbazole under LED@365 nm and LED@405 nm illumination.

[0034] Figure 11 A shows the deep curing apparatus diagram; B shows the TMPTA deep curing results of Os-diphen / Iod / NVK; C shows the TMPTA deep curing results of Os-phen / Iod / NVK. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; the reagents and instruments described, unless otherwise specified, are commercially available.

[0036] Example 1: Synthesis of photosensitizer like Figure 1 The diagram shows the synthetic routes for the electron transfer photosensitizers Os-diphen and Os-phen.

[0037] (1) Synthesis of Os-diphen 664 mg (0.2 mM) of 4,7-diphenyl-1,10-phenanthroline, 320 mg (0.66 mM) of potassium hexachloroosmium tetroxide, 100 mL of ethylene glycol, and 1 mL of N-ethylmorpholine were added to a dry brown single-necked flask. The mixture was stirred to dissolve, and an air condenser was installed. The temperature was raised to 220 °C, and the reaction was allowed to proceed for 10 h. After heating, the reaction solution was allowed to cool to room temperature and then transferred to 100 mL of an aqueous solution containing 2 g of ammonium hexafluorophosphate (6.1 mM). The solution was stirred at room temperature for 1 h. The precipitate in the reaction solution was filtered and washed with water until the filtrate was colorless. The product, after drying and dehydration, was a black solid (453 mg, yield 58%).

[0038] like Figure 2 As shown in A, the 1H NMR spectrum of Os-diphen is: 1 H NMR (400 MHz, DMSO-d6) δ 8.32–8.25(m, 12H), 7.77 (d, J =5.7 Hz, 6H), 7.74–7.61 (m, 24H), 7.64–7.56 (m,6H).

[0039] (2) Synthesis of Os-phen 594 mg (0.3 mM) of 1,10-phenanthroline monohydrate, 480 mg (0.99 mM) of potassium hexachloroosmium tetroxide, 100 mL of ethylene glycol, and 1.5 mL of N-ethylmorpholine were added to a dry brown single-necked flask, stirred to dissolve, and an air condenser was installed. The mixture was heated to 220 °C and reacted for 10 h. After heating, the reaction solution was allowed to cool to room temperature and then transferred to a 150 mL aqueous solution containing 3 g of ammonium hexafluorophosphate (6.1 mM). The solution was stirred at room temperature for 1 h. The precipitate in the reaction solution was filtered and washed with water until the filtrate was colorless. The product, after drying and dehydration, was a black powder (338 mg, yield 47%).

[0040] like Figure 2 As shown in B, the 1H NMR spectrum of Os-phen: 1 H NMR (400 MHz, DMSO d6) δ 8.55 (dd, J=8.3, 1.2 Hz, 6H), 8.38 (s, 6H), 7.99 (dd, J=5.4, 1.2 Hz, 6H), 7.69 (dd, J=8.3, 5.4 Hz, 6H).

[0041] like Figure 3 As shown, both osmium metal complexes exhibit ultraviolet absorption wavelengths up to approximately 700 nm, and both have high molar extinction coefficients in the 250–700 nm region. Os-diphen, in particular, demonstrates superior photophysical properties, with a longer wavelength and a higher molar extinction coefficient. Both osmium metal complexes exhibit red and near-infrared light responsiveness and high spectral utilization.

[0042] Example 2: Ultraviolet Absorption and Photolysis Experiment Prepare Os-diphen and Os-phen at concentrations of 1×10⁻⁶ respectively. -5 A mol / L dichloromethane solution was prepared. The two sets of solutions were transferred to separate quartz cuvettes and, under constant temperature conditions, an LED at 690 nm with a light source of 100 mW / cm² was used. 2 Irradiation intensity was set at timed intervals (0 / 10 / 20 / 30 / 40 / 50 / 60 min), and the absorption spectrum in the range of 250~800 nm was collected immediately after each irradiation using a UV-Vis spectrophotometer.

[0043] Example 3: Ultraviolet Absorption and Photolysis Experiment Prepare Os-diphen and Os-phen at concentrations of 1×10⁻⁶ respectively. -5 mol / L, Iod concentration of 5×10 -4A mol / L dichloromethane mixed solution. The two sets of solutions were transferred separately to quartz cuvettes and, under constant temperature conditions, an LED at 690 nm light source with a wavelength of 100 mW / cm² was used. 2 Irradiation intensity was set at timed intervals (0 / 10 / 20 / 30 / 40 / 50 / 60 s), and the absorption spectrum in the range of 250~800 nm was collected immediately after each irradiation using a UV-Vis spectrophotometer.

[0044] Example 4: Ultraviolet Absorption and Photolysis Experiment Prepare Os-diphen and Os-phen at concentrations of 1×10⁻⁶ respectively. -5 mol / L, Iod concentration of 5×10 -4 mol / L, NVK concentration 1×10 -3 A mol / L dichloromethane mixed solution. The two sets of solutions were transferred separately to quartz cuvettes and, under constant temperature conditions, an LED at 690 nm light source with a concentration of 100 mW / cm² was used. 2 Irradiation intensity was set at timed intervals (0 / 10 / 20 / 30 / 40 / 50 / 60 s), and the absorption spectrum in the range of 250~800 nm was collected immediately after each irradiation using a UV-Vis spectrophotometer.

[0045] like Figure 4 As shown in Example A (Example 2), when only the osmium complex Os-diphen is present in the solution, at a light intensity of 100 mW / cm², 2 Under LED illumination at 690 nm, the characteristic peak of Os-diphen did not change significantly, indicating that it has good photochemical stability.

[0046] like Figure 4 As shown in Example B (Example 3), the two-component reaction kinetics after the introduction of iodonium salt are demonstrated. The system exhibits typical photolysis characteristics: the absorbance in the 408~720 nm region drops sharply by 55% within 60 seconds, accompanied by enhanced absorption in the 296~408 nm region. Clear isoabsorption points appear at 408 nm and 296 nm, confirming that efficient electron transfer occurs between Os-diphen and iodonium salt.

[0047] like Figure 4 As shown in Example C (Example 4), the overall photochemical behavior of the three components—Os-diphen, iodonium salt, and N-vinylcarbazole—under LED @ 690 nm irradiation was qualitatively studied. After adding NVK, the photolysis rate of Os-diphen was significantly slower compared to the two-component model. This is because, in the presence of NVK, Os-diphen is partially regenerated through a redox reaction during irradiation.

[0048] Example 5: Triggering Mechanism Verification The Os-diphen prepared in Example 1 was subjected to ESR testing using electron spin resonance spectroscopy: To clarify the generation of free radicals in the photolysis reaction, the photoinduced electron transfer process of the Os-diphen / iodonium salt system was traced in situ using electron spin resonance spectroscopy. ESR testing was performed on the deoxygenated DMSO solution system under LED excitation at 635 nm (Os-diphen concentration was 1×10⁻⁶). -4 mol L -1 The concentration of iodine salt is 5 × 10⁻⁶. -3 mol L -1 ), and phenyl tert-butyl nitrone (PBN) was used as a free radical scavenger.

[0049] like Figure 5 As shown, a characteristic sixtet signal was detected after 15 min of illumination, with hyperfine coupling constants of aN = 14.8 G and aH = 2.6 G. This spectral characteristic is highly consistent with that of the aryl radical / PBN adduct (Ar· / PBN adduct), directly confirming that a single electron transfer occurs between the excited state Os-diphen and the aryl radical intermediate Ar·.

[0050] Cyclic voltammetry was performed on the degassed dichloromethane solutions of Os-diphen, Os-phen, and Iod prepared in Example 1, as shown in the figure. Figure 6 As shown in Figures A and B, Os-diphen and Os-phen exhibit four distinct redox waves within a potential window of -1.6 to +1.6 V, while Os-phen exhibits three distinct redox wave oxidation potentials. The first oxidation potentials (Eox) of Os-diphen and Os-phen are 0.607 V and 0.592 V vs. SCE, respectively. The excited state energy levels of Os-diphen and Os-phen are 1.74 eV and 1.80 eV, respectively. The cyclic voltammetry curves of Iod are shown below. Figure 6 As shown in Figure C, its reduction potential is Ered = -0.589 V vs. SCE. The Gibbs free energy of the electron transfer reaction is calculated using the following formula: The Gibbs free energy ΔGet of electron transfer from osmium metal complexes to Iod was calculated to be negative, at -0.543 eV and -0.618 eV respectively, indicating that the electron transfer from osmium complexes to Iod in the excited state conforms to the thermodynamic spontaneous condition.

[0051] Figure 7 This is a mechanism diagram of the photopolymerization system, using Os-dipehn / Iod (Ph2I +Taking NVK as an example, the photosensitizer Os-diphen reaches the excited state Os-diphen* after absorbing photons; the excited state Os-diphen* reacts with Ph2I + A redox reaction occurs between them, and the excited state Os-diphen* donates electrons to be oxidized to Os-diphen. ·+ Ph2I + Upon gaining electrons, it is reduced to Ph₂I·; the Ph₂I· radical rapidly undergoes homolytic decomposition, producing highly reactive phenyl radicals (Ph·) and iodobenzene (PhI) as byproducts; the phenyl radical Ph· can undergo a radical addition reaction with NVK to generate the Ph-NVK· reactive intermediate, which can react with Os-diphen ·+ The photosensitizer Os-iphen is regenerated by reducing it to the ground state Os-diphen. Ph-NVK· can further undergo a secondary oxidation reaction with Ph⁂I⁺, losing electrons to generate the cationic species Ph-NVK⁺ and Ph⁂I. + Upon gaining electrons, it is reduced to Ph₂I⁻·, which decomposes to generate phenyl radicals Ph⁻· and iodobenzene. The active initiating species for radical polymerization in the redox cycle are Ph⁻· and Ph-NVK·, while the active initiating species for cationic polymerization are Ph-NVK+ and the oxidation product of the photosensitizer, Os-diphen. ·+ .

[0052] Example 6: Photopolymerization Experiment The influence of the Os-diphen-based photoinitiator on the photopolymerization kinetics of TMPTA was investigated using a real-time Fourier transform infrared spectroscopy (RT-FTIR) system. The differences in initiation efficiency among single-component (Os-diphen), two-component (Os-diphen / Iod), and three-component (Os-diphen / Iod / NVK) systems were examined. Experiments were conducted using a red LED at 690 nm (280 mW cm⁻¹). -2 The polymerization was carried out under irradiation. The initiation system is shown in Table 1, and the monomer for polymerization is TMPTA.

[0053] Table 1: TMPTA Polymerization Experiment like Figure 8 As shown in Figure A, in a single-component system (containing only 0.5 wt% Os-diphen), the double bond conversion rate of TMPTA was extremely low (<5%) after 600 seconds of LED @ 690 nm illumination. This indicates that although excited-state Os-diphen* can initiate monomer polymerization through direct electron transfer, its initiation efficiency is very limited.

[0054] like Figure 8As shown in Figure B, the photoinitiation efficiency was significantly improved after introducing iodine salt (Iod, 2 wt%) to form a two-component system. The performance of this system exhibited a clear concentration dependence: as the Os-diphen concentration increased from 0.1 wt% to 1.0 wt%, the final conversion rate initially increased and then decreased. The system performed optimally when the Os-diphen concentration was 0.5 wt%, with the polymerization reaction reaching a conversion plateau within 100 seconds.

[0055] like Figure 8 As shown in Figure C, the photopolymerization performance was comprehensively enhanced after further adding the co-initiator NVK (3 wt%) to form a three-component system. The final conversion and polymerization rate of formulations with different Os-diphen concentrations were superior to the corresponding two-component systems. At the ratio (Os-diphen / Iod / NVK = 0.5 wt% / 2 wt% / 3 wt%), the final double bond conversion reached 51%, and the reaction kinetics were significantly accelerated, reaching a plateau within 50 seconds. This performance improvement is attributed to the unique photosensitizer regeneration cycle mechanism and the combined initiation effect of the Ph-NVK·active free radical in the three-component system.

[0056] The above experimental results fully demonstrate that the Os-diphen / Iod / NVK ternary photoinitiation system exhibits excellent photoinitiation performance under LED@690 nm red light irradiation. Based on the broad-spectrum absorption characteristics of Os-diphen in the 300-700 nm range, the universality of this system is further verified.

[0057] like Figure 9 As shown, the Os-diphen / Iod / NVK ternary system can achieve rapid curing of TMPTA monomers under irradiation with various wavelengths of light sources, including LEDs at 365 nm (UV), 405 nm (UV), 450 nm (blue), 535 nm (green), and 635 nm (red), demonstrating full-band photoresponse capability. In particular, under 365 nm UV irradiation, the double bond conversion rate increased to 69%, an 18% improvement compared to 690 nm red light irradiation.

[0058] The above results indicate that the Os-diphen photoinitiation system exhibits excellent initiation performance across the entire wavelength range.

[0059] Example 7: Photopolymerization Experiment Based on the fact that the Os-diphen / Iod / NVK ternary system can generate Ph-NVK+ and Os-diphen·+ during the redox cycle, it has the ability to initiate cationic polymerization. This photoinitiation system is further applied to the cationic ring-opening polymerization of epoxy monomer EPOX.

[0060] The initiation of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (EPOX) by the three-component system was verified using essentially the same method as in Example 6. Light source: LED @ 365 nm (240 mW cm⁻¹) -2 LED@405 nm (210 mW cm⁻¹) -2 ); Photoinitiation system: Os-diphen, iodonium salt (Iod), N-vinylcarbazole (NVK), in the following ratio (Os-diphen / Iod / NVK = 0.5 wt% / 2 wt% / 3 wt%).

[0061] The cationic ring-opening polymerization of epoxy monomer EPOX using the Os-diphen / Iod / NVK three-component system is as follows: Figure 10 As shown, under LED@365 nm ultraviolet irradiation, the final conversion rate of EPOX reached 42%, indicating a relatively fast polymerization rate; under LED@405 nm ultraviolet irradiation, the final conversion rate was 28%. The conversion rate at LED@365 nm was 14% higher than that at LED@405 nm. This trend is consistent with the free radical polymerization results of TMPTA, mainly attributed to the fact that ultraviolet light has higher energy, which can more effectively drive the excitation of photosensitizers and subsequent electron transfer processes.

[0062] However, compared to the free radical polymerization of TMPTA (with a maximum conversion of 51% and a plateau within 50 seconds), the cationic polymerization efficiency of EPOX is generally lower. This may be because the formation mechanism of cationic active species (such as Ph-NVK⁺) is more complex, requiring multiple electron transfer and free radical addition reactions, resulting in a longer kinetic pathway and thus a relatively lower initiation efficiency.

[0063] Example 8: Deep curing The TMPTA prepolymer of Os-diphen / Iod / NVK (0.5 wt% / 2 wt% / 3 wt%) and Os-phen / Iod / NVK (0.5 wt% / 2 wt% / 3 wt%) was injected into a quartz glass tube (7 mm inner diameter), and after static degassing treatment, it was used with a light intensity of 1.1 W / cm². 2 Irradiate vertically with a 690 nm laser for 15 minutes, such as Figure 11 As shown in Figure A, the pipe wall is wrapped with aluminum foil to eliminate lateral light scattering interference.

[0064] like Figure 11As shown in Figure B, after 15 minutes of 690 nm laser irradiation, the TMPTA prepolymer of Os-diphen / Iod / NVK was completely cured, with a curing depth reaching 23 μm. The deep curing results of the TMPTA from Os-phen / Iod / NVK are shown in Figure B. Figure 11 As shown in C, the average curing depth is 10 m.

[0065] In summary, this invention, by constructing a three-component photo-redox initiation system using Os-diphen, Os-phen with iodonium salt (Iod), and N-vinylcarbazole (NVK), demonstrates that this system can efficiently initiate the free radical polymerization of acrylates (such as TMPTA) and the cationic polymerization of epoxy resins (such as EPOX) across a broad spectral range of 365 nm to 690 nm. In particular, this system exhibits excellent deep-curing capability (up to 23 cm) and high conversion rate (51% double bond conversion rate) under near-infrared light (690 nm) irradiation, and successfully achieves sunlight-driven polymerization. This invention effectively overcomes the inherent defects of traditional ultraviolet photoinitiation systems, such as insufficient light penetration depth and low spectral utilization, providing a novel solution for developing efficient, green, and biocompatible advanced photopolymerization technologies suitable for thick-section materials and biocompatible applications.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A photoinitiator composition characterized in that, The photoinitiator composition comprises an osmium metal complex and an iodonium salt; The osmium metal complex serves as an electron transfer type photosensitizer in a photopolymerization system; The osmium metal complex is one or a combination of compounds represented by formula (I) or formula (II): (I) and (II).

2. The photoinitiator composition according to claim 1, characterized in that The photoinitiator composition further comprises N-vinylcarbazole.

3. The photoinitiator composition according to claim 1, wherein The osmium metal complex is added in an amount of 0.1 wt% to 1 wt% and the iodonium salt is added in an amount of 1 wt% to 3 wt%, based on the total mass of the polymerizable monomers.

4. The photoinitiator composition according to claim 2, wherein The osmium metal complex is added in an amount of 0.1 wt% to 1 wt%, the iodonium salt is added in an amount of 1 wt% to 3 wt%, and the N-vinylcarbazole is added in an amount of 2 wt% to 4 wt%, based on the total mass of the polymerizable monomers.

5. Photopolymerization method based on the photoinitiator composition according to claim 1 or 3, characterized in that, The photoinitiator composition initiates free radical polymerization of the monomers under irradiation of light with a wavelength of 200-700 nm.

6. Photopolymerization method based on the photoinitiator composition according to claim 2 or 4, characterized in that, The photoinitiator composition initiates free radical polymerization, cationic polymerization, or hybrid polymerization of the monomers under irradiation of light with a wavelength of 200-700 nm.

7. Photopolymerization process according to claim 5 or 6, characterized in that, The monomers include acrylate monomers, epoxy monomers, and vinyl ether monomers.

8. The photopolymerization method according to claim 7, characterized in that, The acrylate monomers are selected from one or more of tripropyleneglycol diacrylate, trimethylolpropane triacrylate, and methyl acrylate; The epoxy monomers are 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate; The vinyl ether monomers are n-butyl vinyl ether.

9. Photopolymerization process according to any one of claims 5 to 8, characterized in that, The monomers have a curing depth of ≥10 cm under irradiation of light with a wavelength of 690 nm; preferably, the curing depth is ≥20 cm.

10. The photopolymerization method according to claim 8, characterized in that, The double bond conversion rate of the polymerized monomers is not less than 50% when the monomers are trimethylolpropane triacrylate under irradiation of light with a wavelength of 690 nm.

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