A high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane and a preparation method thereof

Abstract

The application provides a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane and a preparation method thereof, and belongs to the technical field of holographic storage materials, and aims to solve the technical problem of poor photosensitivity of photopolymer materials.The application comprises the following steps: (1) uniformly mixing acrylate monomers, multi-vinyl crosslinking agents, thermal initiators and photoinitiators to obtain a mixed solution; (2) heating the mixed solution to perform a prepolymerization reaction; and (3) performing a thermal polymerization reaction on the prepolymer to obtain the high-sensitivity photopolymer holographic storage material.The application successfully prepares the high-sensitivity photopolymer holographic storage material with a crosslinked macromolecular matrix and rich vinyl groups by adding cyclotetrasiloxane (V4D4) containing four vinyl groups, greatly improves the photosensitivity (more than 3 times) and diffraction efficiency (about 50%) of the material, and realizes the effect of fast data storage (4s storage and 4% bit error rate).

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of holographic storage materials, and particularly relates to a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane and a preparation method thereof. BACKGROUND

[0002] With the rapid development of information science, scientists predict that the total data volume of the world will exceed 175 ZB by 2025. In the face of the storage demand of massive data, storage technology has attracted widespread attention. At present, the mainstream storage technology in the world is mainly magnetic storage, but it has problems such as low recording density, slow reading speed, high maintenance cost, large power consumption, and short storage time. Therefore, companies such as Facebook that have large data centers need to build large-scale servers. The writing and reading processes of the servers will generate a large amount of heat. In order to dissipate the heat of the servers, some companies even install the servers in the seabed or build special places, thus increasing the total cost. However, the explosive growth of data volume has obviously made the magnetic storage technology unable to meet the needs of human development. In the late 1960s, optical storage technology was invented. After the development of several generations of products such as CD, VCD, DVD and BD, the direction of information storage has shifted from breaking the diffraction limit to high-density storage. However, the storage method is still limited to two-dimensional bit storage. Even though multi-layer storage optical discs have appeared, the number of layers is limited, and the transmission rate and recording size cannot meet the requirements of large data storage. Therefore, multi-dimensional storage methods are favored.

[0003] Holographic storage technology is a technology that can record all information such as amplitude, phase and polarization information of light. It uses light waves as carriers and can realize wavelength multiplexing, displacement multiplexing, angle multiplexing and polarization multiplexing. At the same time, it breaks through the two-dimensional storage method and realizes three-dimensional storage with a theoretical storage density of 1 / λ3. Since the storage density has been improved by one dimension, the storage density will be improved by several orders of magnitude, and the storage capacity will be greater than 1 TB / dics. This breakthrough is expected to meet the needs of today's era for massive data storage. Throughout the history of holographic storage technology, every major development is inseparable from the progress and innovation of materials.

[0004] The quality of a hologram depends largely on the photosensitive properties of the recording material. Therefore, the selection of the storage material plays a crucial role in the development of volume holographic storage technology, and is directly related to the quality of data storage and reading and whether the related products can be commercialized. An ideal storage material should have high sensitivity (>500 cm / J), fast response speed, high modulation (refractive index modulation >5×10-3), low shrinkage (<0.5%), large dynamic range, and good fidelity of reproduced images.

[0005] Photopolymers have been widely concerned by researchers since they were first proposed decades ago because of their good material properties as recording media for holographic storage. Researchers mainly change the composition of monomers and initiators in the material, as well as add different nanoparticles, to achieve the material properties they want, such as improving the diffraction efficiency of the material, the refractive index modulation, and reducing the shrinkage caused by polymerization, etc.

[0006] In 1969, Close et al. (Close D H, Jacobson AD, Margerum J D, et al. Hologram recording on photopolymer materials [J]. Applied Physics Letters, 1969, 14(5): 159-160) first proposed a photopolymer liquid material made of acrylamide (AA) as a monomer and methylene blue as a photocatalyst, and applied it to holographic storage. Subsequently, in 1975, French scientists Jeudy et al. (Jeudy M J, Robillard J J. Spectral photosensitization of a variable index material for recording phase holograms with high efficiency [J]. Optics Communications, 1975, 13(1): 25-28) improved the experimental system of Close's research group by adding polyvinyl alcohol (PVA) binder to prepare a dry photopolymer film. The recorded grating had a diffraction efficiency of up to 80%, high refractive index modulation, fast photopolymerization speed, and was simple to prepare and low in cost. However, AA has strong hydrophilicity and is prone to deliquescence, and long-term contact with the human body can cause cancer, so it is necessary to find a healthy and environmentally friendly material.

[0007] Compared with AA, polyacrylate photopolymer has better stability and more choices. Methyl methacrylate, ethyl acrylate, lauryl acrylate, etc. are commonly used. As early as the 1980s, scientists found that quinones can be used as photoinitiators. In 1986, Zhang J et al. (Zhang J, Yu B K, Wang C H, et al. Holographic grating relaxation studies of camphorquinone diffusion in a polystyrene host [J]. The Journal of Physical Chemistry, 1986, 90(7): 1299-1301) added camphorquinone molecules to polymethyl methacrylate and studied its diffusion phenomenon. Until 1996, Veniaminov A. V and Sedunov Y. N (Veniaminov A V, Sedunov Y N. Diffusion of Phenanthrenequinone in Poly(methylmethacrylate): Holographic Measurements [J]. Polymer Science Ser. A., 1996, 38(1): 59-63) first prepared a photopolymer film of phenanthrenequinone (PQ) doped methyl methacrylate (PQ / PMMA) with a thickness of 100-900 μm by spin coating. By measuring the change of the optical properties of the holographic grating with time, the diffusion coefficient of the photosensitizer PQ molecules in the polymer sample in the state of viscous liquid, rubber and glass was calculated at a temperature of 20-270℃, and the diffusion coefficient in the three states changed in the range of 10 -21 ~10 -11 m 2s. Although this experimental group only analyzed the diffusion behavior of photosensitizer PQ in the polymer, did not further study the holographic storage performance of the material, but for the preparation of quinone molecules as photosensitive components, PMMA for the substrate of photopolymer opened up a new era, for the later continue to PQ / PMMA polymer research laid a good experimental and theoretical basis. Based on the previous research, Steckman G.J. et al (Steckman G J, Solomatine I, Zhou G, et al. Characterization of phenanthrenequinone-doped poly(methyl methacrylate) for holographic memory [J]. Optics letters, 1998, 23(16): 1310-1312) in 1996, PQ and thermal initiator mixed in methyl methacrylate (MMA) by high temperature and high pressure thermal initiation polymerization method prepared millimeter level disc sample, and tested the single grating diffraction efficiency can reach 35%, 3mm after the material single point multiplexing 50 holographic dynamic range of 4.8. Experimental results show that the material has good optical properties, shrinkage is extremely low can be ignored, but the photosensitivity is only 4.76J / cm 2 , refractive index modulation degree is low, 1mm thick material is only 3.25×10 -4 .

[0008] In order to improve the effective thickness of the material and reduce the shrinkage, so as to increase the storage capacity. In 2000, Lin S.H et al. (Lin S H, Hsu KY. Temperature Effect in PQ-PMMA Photopolymer [J]. Proceeding of SPIE, 2000, 4110: 77-83) by separating the preparation method of thermal polymerization and photopolymerization, first through the thermal polymerization to form PMMA substrate, and then through the external writing angle 32° to carry out photopolymerization recording holographic grating, single point reusable 355 holographic grating, 8mm thick material dynamic range can reach 14, can achieve the performance index of large capacity holographic storage. Subsequently in 2004, Hsiao Y.N et al. (Hsiao YN, Whang W T, Lin S H. Analyses on Physical Mechanism of Holographic Recording in Phenanthrenequinone-Doped Poly(methyl methacrylate) Hybrid Materials [J]. Optical Engineer, 2004, 43(9): 1993-2002) using chemical measurement method for further analysis of the material light reaction, found that the change of the structure from isotropic to anisotropic before and after PQ exposure is the main reason for the change of the refractive index of the material, and the main photo product is the one-to-one reaction of PQ molecules and PMMA. In 2005, Veniaminov A.V et al. (Veniaminov AV, Bartsch E, Popov A P. Postexposure Evolution of a Photoinduced Grating in a Polymer Material with Phenanthrenequinone [J]. Optics and spectroscopy, 2005, 99(5): 744-750) studied the special properties of the holographic grating established in the PQ / PMMA material after exposure, and investigated the diffusion behavior of various components in the long-term evolution of the grating. It is proposed that the time evolution process of the grating is divided into four stages: (1) the initial light-sensitive agent absorbs light energy to form free excitons, which leads to nonlinear changes of the grating, and photo-linking conversion to stable photo products with macromolecules; (2) PQ molecule diffusion causes the enhancement of hologram; (3) the movement of polymer chains is limited by space, which causes rapid partial decay of the grating; (4) macromolecular diffusion leads to slow decay of the grating. This analysis provides an important basis for in-depth study of the photochemical reaction process of polymer samples.

[0009] In recent years, due to the continuous development of holographic devices and storage technology, the photopolymer of acrylate monomer is proved to be a good holographic storage material. In order to better improve the storage characteristics of the material, researchers begin to devote to improve the base composition or doped nanoparticles to improve the holographic performance of PQ / PMMA. In 2002, Suzuki N. and Tomita Y (Suzuki N, Tomita Y, Kojima T. Holographic recording in TiO2 nanoparticle-dispersed methacrylate photopolymer films [J]. Applied Physics Letters. 2002, 81(22): 4121-4123) first doped TiO2 nanoparticles into PQ / PMMA material, found that adding TiO2 nanoparticles and monomer will produce mutual diffusion phenomenon, monomer and nanoparticles are uniformly distributed before exposure, after exposure, monomer begins to polymerize, bright and dark area produces concentration difference, dark area will diffuse to the bright area. Because of the chemical potential effect between monomer and nanoparticles, the nanoparticles will diffuse from the bright area to the dark area, thereby reducing the density difference between monomer and polymer, directly reducing the shrinkage phenomenon caused by the photochemical reaction of the material. The research group also tested the holographic performance of the material, and found that under the wavelength of 532 nm coherent light, the diffraction efficiency and photosensitivity of the material have been greatly improved, which makes many researchers begin to pay attention to the research of nano-doped materials. Subsequently in 2004, both of them further added SiO2 nanoparticles into the methacrylate polymer, and obtained more than 98% grating diffraction efficiency (Suzuki N, Tomita Y. Silica-nanoparticle-dispersed methacrylate photopolymers with net diffraction efficiency near 100% [J]. Applied Optics, 2004, 43(10): 2125-2129).

[0010] By summarizing the experience of predecessors, Hsiao Y.N et al. (Hsiao YN, Whang W T, Lin S H. Effect of ZnMA on Optical and Holographic Characteristics of Doped PQ / PMMA Photopolymer [J]. Japanese Journal of Applied Physics, 2005, 44(2): 914-919) in 2005 added ZnMA into PQ / PMMA photopolymer, found that the addition of organometallic can improve the holographic characteristics of the material, the experimental data found that the response speed of the material has been significantly improved, the appropriate concentration of ZnMA can improve the diffraction efficiency. In 2006, Suzuki N. and Tomita Y (Suzuki N, Tomita Y, Ohmori K. et al. Highly transparent ZrO2 nanoparticle-dispersed acrylate photopolymers for volume holographic recording [J]. Optics Express, 2006, 14(26): 12712-12719) by adding the appropriate solubility of ZrO2, found that the scattering coefficient is reduced by more than 30 times than TiO2 doped and the refractive index degree is greater, and again proved that the doping of nanoparticles can effectively reduce the shrinkage and improve the material life. Subsequently in 2008, Goldenberg L.M et al. (Goldenberg L M, Sakhno OV, Smirnova T N, et al. Holographic Composites with Gold Nanoparticles: Nanoparticles Promote Polymer Segregation [J]. Chemistry of Materials, 2008, 20(14): 4619-4627) by mixing chemically modified gold nanoparticles with acrylate monomers with carboxyl functional groups, prepared photopolymer material doped with gold nanoparticles. Experiments found that gold nanoparticles help to slow down the photopolymerization of free radicals, through the redistribution of gold nanoparticles and monomers and the change of surface relief depth, nanoparticles can affect the material structure, so as to inhibit the shrinkage and make the material more stable.In 2013, the Shanghai University of Science and Technology team added liquid crystal particles to the trimethylolalkane triacrylate prepolymer, and the measured grating diffraction efficiency was stable at 90% (Zhang M, Zheng J, Gui K, et al. Electro-optical characteristics of holographic polymer dispersed liquid crystal gratings doped with nanosilver [J]. Applied Optics, 2013, 52(31): 7411-7418). In 2014, Li C. et al. (Li C, Cao L, Wang Z, et al. Hybrid polarization-angle multiplexing for volume holography in gold nanoparticle-doped photopolymer [J]. Optics Letters, 2014, 39(24): 6891-6894) developed a holographic kinetics model, which described the behavior of gold nanoparticles in the process of multi-component diffusion and the formation of absorption gratings in the process of holographic exposure, and described the kinetics of gold nanoparticle (NPs) doped photopolymer hybrid grating, and achieved circular polarization-angle multiplexing holographic image recording in the prepared gold nanoparticle doped photopolymer material. In 2018, Liu P et al. (Liu P, Zhao Y, Li Z, et al. Improvement of ultrafast holographic performance in silver nanoprisms dispersed photopolymer [J]. Optics Express, 2018, 26(6): 6993-7004) prepared a photopolymer doped with silver nanoprisms, and under the exposure of an ultrafast nanosecond laser, the optimized grating diffraction efficiency reached 51.4%. The long-term stability of the composite grating was quantitatively described, and the improvement of the storage stability of the holographic grating by the copolymerization substrate P(MMA-co-MAA) was described. In 2019, Liu Y. et al. used liquid-phase laser ablation technology to directly prepare Al nanoparticles in the polymer monomer MMA, reducing the complexity of the substrate composition, and under traditional holographic recording, the diffraction efficiency could be improved to 60%, and under orthogonal linear polarized light holographic recording, the diffraction efficiency could be improved from 0.6% to 4.6%.

[27]

[0011] ​PQ / PMMA is considered as a photopolymer material with good optical performance through years of research and investigation, and has great development and application prospect in the field of holographic recording because of its simple preparation process, low raw material cost, low volume shrinkage, controllable thickness size and polarization recording capacity. However, the diffraction efficiency of PQ / PMMA material is not high, the refractive index modulation is limited, and especially the low photosensitivity becomes a major obstacle for its commercial application. Therefore, while retaining the above advantages of PQ / PMMA material, developing a storage material capable of rapidly performing photo-reaction in the bright area and having a large refractive index modulation between the reaction product and the material in the dark area has become the key to realize the commercial application of holographic storage technology. SUMMARY

[0012] In order to solve the technical problem of poor photosensitivity of the photopolymer material, the application provides a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane and a preparation method thereof, and successfully prepares the high-sensitivity photopolymer holographic storage material with a crosslinked macromolecular matrix and rich vinyl groups, and realizes the effect of fast data storage.

[0013] In order to achieve the above purpose, the technical scheme of the application is as follows:

[0014] A preparation method of a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane, comprising the following steps:

[0015] (1) uniformly mixing acrylate monomers, multi-vinyl crosslinking agents, thermal initiators and photoinitiators to obtain a mixed solution;

[0016] (2) heating the mixed solution to perform a prepolymerization reaction;

[0017] (3) performing a thermal polymerization reaction on the prepolymer obtained in step (2) to obtain the high-sensitivity photopolymer holographic storage material.

[0018] The acrylate monomer is any one of methyl methacrylate, ethyl acrylate or lauryl acrylate.

[0019] The multi-vinyl crosslinking agent is tetramethyl tetravinyl cyclotetrasiloxane.

[0020] The thermal initiator is azobisisobutyronitrile.

[0021] The photoinitiator is phenanthraquinone.

[0022] The multi-vinyl crosslinking agent accounts for 5-15% of the mass sum of the acrylate monomers and the multi-vinyl crosslinking agent; the thermal initiator and the photoinitiator each accounts for 0.5-2% of the mass sum of the acrylate monomers and the multi-vinyl crosslinking agent.

[0023] The temperature of the prepolymerization reaction is 60-70℃, the reaction time is 60-70min, and the prepolymerization reaction is carried out under stirring.

[0024] The temperature of the thermal polymerization reaction is 60-65℃, and the reaction time is 20-22h.

[0025] In step (3), the prepolymer obtained in step (2) is poured into a mold for sealing, and then the thermal polymerization reaction is carried out, and after the reaction is completed, the mold is demolded.

[0026] The beneficial effects of the present application are:

[0027] In the preparation of the photopolymer, in the water bath stirring stage, V4D4 needs a higher polymerization temperature and is not activated by the thermal initiator, so it does not participate in the prepolymerization reaction, and only chain PMMA polymer is generated in the prepolymerization; in the baking stage, V4D4 is initiated to polymerize by the high temperature released by the polymerization, cross-linking reaction occurs with PMMA chain, and a large number of remaining vinyl groups are generated. The present application avoids the complete reaction of the vinyl-rich group material in the free radical polymerization process, effectively improves the photosensitivity of the material by increasing the concentration of the active group (vinyl group), and greatly improves the photosensitivity of the prepared high-sensitivity photopolymer holographic storage material from 0.27cm / J to 0.92cm / J (more than 3 times) and the diffraction efficiency from 47.5% to 72.7% (~50%) under the exposure conditions of a single-beam 25mW diameter 0.5mm 532nm laser at a double-beam interference angle of 24°, realizing the effect of fast data storage (4s storage, error rate 4%. Exposure conditions 0.17mW, 200μm diameter, 532nm spot). BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0029] Figure 1 The preparation process of the high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane.

[0030] Figure 2 The main product of the high-sensitivity photopolymer holographic storage material.

[0031] Figure 3 The elution curve of different V4D4 doping concentrations in Examples 1-4 and Comparative Example 1.

[0032] Figure 4THF solubility effect of the polymer after water bath polymerization (red label) and baking polymerization (yellow label) of different V4D4 concentrations.

[0033] Figure 5 Raman spectrum of the polymer of different V4D4 doping concentrations for Examples 1-4 and Comparative Example 1.

[0034] Figure 6 Diffraction efficiency curve of different V4D4 doping concentrations for Examples 1-4 and Comparative Example 1

[0035] Figure 7 Photosensitivity and saturated diffraction efficiency of different V4D4 doping concentrations for Examples 1-4 and Comparative Example 1,

[0036] Figure 8 Response time and double bond content of the polymer of different V4D4 doping concentrations for Examples 1-4 and Comparative Example 1.

[0037] Figure 9 Holographic data storage effect diagram of the photopolymer holographic storage material prepared in Example 3 and Comparative Example 1, wherein a is the read data page of the V4D4-PQ / PMMA material stored for 4s; and b is the read data page of the PQ / PMMA material stored for 8s. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0039] Example 1

[0040] A preparation method of a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane, as shown in Figure 1 specifically includes the following steps:

[0041] (1) 18.8 g of a polymer monomer-methyl methacrylate (MMA), 1.2 g of a multi-vinyl crosslinking agent-tetramethyl tetravinyl cyclotetrasiloxane (V4D4), 0.2 g of a thermal initiator-azobisisobutyronitrile (AIBN), and 0.2 g of a photoinitiator-phenanthrenequinone (PQ) are weighed according to the proportion. The weighed raw materials are placed in a brown reaction bottle and subjected to ultrasonic oscillation at 60°C and 60HZ for 10 min to uniformly mix and fully dissolve the materials.

[0042] (2) Place the thoroughly mixed and dissolved yellow transparent solution into a water bath with a magnetic stirrer. Heat the solution at 60°C and 900 R / min for 70 minutes until the transparent solution becomes a viscous substance resembling glycerol. At this point, only short-chain polymer PMMA (polymethyl methacrylate) is formed in the polymer. The carbon-carbon double bond of V4D4 is relatively stable and does not participate in the thermal polymerization reaction to form a cross-linked macromolecular structure.

[0043] (3) The viscous liquid is injected into the mold. In this patent, a square sheet of polytetrafluoroethylene is used as a support and two pieces of glass are used to seal the sheet material mold, which is 1.5 mm thick. In other embodiments, other molds can also be used to make the desired polymer block material.

[0044] (4) The filled mold is pressed and placed in a constant temperature drying oven for heating. The material is heated at 60°C for 22 hours to complete the final polymerization and molding. The polymerization reaction is relatively intense during this process, and a high-sensitivity photopolymer holographic storage material is generated with V4D4 as the crosslinking agent as the crosslinking macromolecule as the matrix and vinyl groups on unreacted V4D4 as the main active substances.

[0045] (5) After heating and molding, cool to room temperature, place in a -3℃ refrigerator for 3 minutes to demold, and a smooth sheet-like photopolymer holographic storage material will be obtained. Its structural schematic diagram is shown below. Figure 2 As shown, the polymer is based on cross-linked macromolecules, containing uncross-linked C=C bonds, some PMMA chains, and a small amount of MMA monomers. PQ is uniformly distributed in the material and will preferentially undergo photoreaction with uncross-linked C=C bonds.

[0046] Example 2

[0047] A method for preparing a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane, such as Figure 1 As shown, the specific steps include:

[0048] (1) Weigh out 18.4g of the monomer methyl methacrylate (MMA), 1.6g of the polyvinyl crosslinking agent tetramethyltetravinylcyclotetrasiloxane (V4D4), 0.2g of the thermal initiator azobisisobutyronitrile (AIBN), and 0.2g of the photoinitiator phenanthrenequinone (PQ) according to the specified proportions. Place the weighed raw materials into a brown reaction bottle and ultrasonically vibrate at 60℃ and 60HZ for 10 minutes to ensure that the materials are uniformly mixed and fully dissolved.

[0049] (2) Put the yellow transparent solution that is mixed uniformly and dissolved fully into a water bath kettle with magnetic stirring, and use 60°C and 900R / min to stir and heat, water bath heating for 70 min until the transparent solution becomes a glycerol-like viscous material. At this time, only short-chain polymer PMMA (polymethyl methacrylate) is generated in the polymer, and the carbon-carbon double bond of V4D4 is relatively stable and does not participate in the thermal polymerization reaction to generate a cross-linked macromolecular structure.

[0050] (3) Pour the viscous liquid into a mold, and use a square sheet of polytetrafluoroethylene as a support, and seal two pieces of glass to form a sheet material mold with a thickness of 1.5 mm. In other embodiments, other molds can also be used to form the required polymer block material.

[0051] (4) Put the filled mold into a constant temperature air drying oven for heating, and the material is heated at 60°C for 22h to complete the final polymerization molding. During this process, the polymerization reaction is relatively intense, and a cross-linked macromolecule based on V4D4 as a cross-linking agent and a high-sensitivity photopolymer holographic storage material based on the unreacted vinyl group on V4D4 as the main active substance is generated.

[0052] (5) After heating and molding, cool to room temperature, and put into a -3°C refrigerator for 3 min for demolding to obtain a sheet-shaped photopolymer holographic storage material with a smooth surface.

[0053] Example 3

[0054] A preparation method of a high-sensitivity photopolymer holographic storage material based on cyclosiloxane, as shown in Figure 1 , specifically includes the following steps:

[0055] (1) Weigh 18g of polymer monomer-methyl methacrylate (MMA), 2g of multi-vinyl cross-linking agent-tetramethyl tetravinyl cyclosiloxane (V4D4), 0.2g of thermal initiator-azobisisobutyronitrile (AIBN), and 0.2g of photoinitiator phenanthraquinone (PQ). Put the weighed raw materials into a brown reaction bottle, and perform ultrasonic oscillation at 60°C and 60HZ for 10 min to uniformly mix and fully dissolve the materials.

[0056] (2) Put the yellow transparent solution that is mixed uniformly and dissolved fully into a water bath kettle with magnetic stirring, and use 60°C and 900R / min to stir and heat, water bath heating for 70 min until the transparent solution becomes a glycerol-like viscous material. At this time, only short-chain polymer PMMA (polymethyl methacrylate) is generated in the polymer, and the carbon-carbon double bond of V4D4 is relatively stable and does not participate in the thermal polymerization reaction to generate a cross-linked macromolecular structure.

[0057] (3) The viscous liquid is injected into the mold. In this patent, square sheet polytetrafluoroethylene is used as support, and two pieces of glass are sealed to form a sheet material mold with a thickness of 1.5 mm. In other embodiments, other molds can also be used to make the desired polymer block material.

[0058] (4) The filled mold is tightly placed into a constant temperature air drying oven for heating. The material is heated at 60°C for 22h to complete the final polymerization molding. During this process, the polymerization reaction is relatively intense, and a cross-linked macromolecule based on V4D4 as the cross-linking agent is generated, and the ethylene group on the unreacted V4D4 is the main active substance of the high-sensitivity photopolymer holographic storage material.

[0059] (5) After heating and molding, it is cooled to room temperature and placed in a -3°C refrigerator for 3 minutes for demolding, and a sheet-shaped photopolymer holographic storage material with a smooth surface is obtained.

[0060] Example 4

[0061] A preparation method of a high-sensitivity photopolymer holographic storage material based on cyclosiloxane, as shown in Figure 1 , specifically comprising the following steps:

[0062] (1) 17.6g of polymer monomer-methyl methacrylate (MMA), 2.4g of multi-vinyl cross-linking agent-tetramethyl tetravinyl cyclosiloxane (V4D4), 0.2g of thermal initiator-azobisisobutyronitrile (AIBN) and 0.2g of photoinitiator phenanthraquinone (PQ) are weighed according to the proportion. The weighed raw materials are placed in a brown reaction bottle and subjected to ultrasonic oscillation at 60°C and 60HZ for 10 minutes to uniformly mix and fully dissolve the materials.

[0063] (2) The uniformly mixed and fully dissolved yellow transparent solution is placed in a water bath with magnetic stirring, and is stirred and heated at 60°C and 900R / min. The water bath is heated for 70 minutes until the transparent solution becomes a viscous substance like glycerin. At this time, only short-chain polymer PMMA (polymethyl methacrylate) is generated in the polymer, and the carbon-carbon double bond of V4D4 is relatively stable and does not participate in the thermal polymerization reaction to generate a cross-linked macromolecular structure.

[0064] (3) The viscous liquid is injected into the mold. In this patent, square sheet polytetrafluoroethylene is used as support, and two pieces of glass are sealed to form a sheet material mold with a thickness of 1.5 mm. In other embodiments, other molds can also be used to make the desired polymer block material.

[0065] (4) Put the filled mold into the constant temperature air drying oven for heating. The material is heated at 60°C for 22h to complete the final polymerization molding. The polymerization reaction is relatively intense in this process, and the high-sensitivity photopolymer holographic storage material is generated with cross-linked macromolecules as the matrix and the unreacted vinyl on V4D4 as the main active substance.

[0066] (5) After heating molding, cool to room temperature, and put into a -3°C refrigerator for 3min to demold. The surface-finished sheet-shaped photopolymer holographic storage material is obtained.

[0067] Example 5

[0068] A preparation method of a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane, as shown in Figure 1 , specifically includes the following steps:

[0069] (1) Weigh 17.5g of polymer monomer-methyl methacrylate (MMA), 2.5g of multi-vinyl crosslinking agent-tetramethyl tetravinyl cyclotetrasiloxane (V4D4), 0.1g of thermal initiator-azobisisobutyronitrile (AIBN), and 0.1g of photoinitiator phenanthraquinone (PQ) according to the proportion. Put the weighed raw materials into a brown reaction bottle, and perform ultrasonic oscillation at 60°C and 60HZ for 10min to uniformly mix and fully dissolve the materials.

[0070] (2) Put the uniformly mixed and fully dissolved yellow transparent solution into a water bath kettle with magnetic stirring, and use 70°C and 900R / min conditions for stirring and heating. The water bath is heated for 65min until the transparent solution becomes a glycerol-like viscous substance. At this time, only short-chain polymer PMMA (polymethyl methacrylate) is generated in the polymer, and the carbon-carbon double bond of V4D4 is relatively stable and does not participate in the thermal polymerization reaction to generate a cross-linked macromolecular structure.

[0071] (3) Inject the viscous liquid into the mold. In this patent, square sheet-shaped polytetrafluoroethylene is used as the support, and two pieces of glass are sealed to form a sheet-shaped material mold with a thickness of 1.5mm. In other embodiments, other molds can also be used to make the required polymer block materials.

[0072] (4) Put the filled mold into the constant temperature air drying oven for heating. The material is heated at 65°C for 20h to complete the final polymerization molding. The polymerization reaction is relatively intense in this process, and the high-sensitivity photopolymer holographic storage material is generated with cross-linked macromolecules as the matrix and the unreacted vinyl on V4D4 as the main active substance.

[0073] (5) After the heating forming is completed, cool to room temperature, put into -3℃ refrigerator to cool for 3 min to demold, and a sheet-shaped photopolymer holographic storage material with smooth surface can be obtained.

[0074] Example 6

[0075] A preparation method of a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane, as shown in the figure, specifically includes the following steps: Figure 1

[0076] (1) Take 17g of polymer monomer-methyl methacrylate (MMA), 3g of multi-vinyl crosslinking agent-tetramethyl tetravinyl cyclotetrasiloxane (V4D4), 0.4g of thermal initiator-azobisisobutyronitrile (AIBN), and 0.4g of photoinitiator phenanthraquinone (PQ) according to the proportion. Put the weighed raw materials into a brown reaction bottle, and perform ultrasonic oscillation at 60℃ and 60HZ for 10min to uniformly mix and fully dissolve the materials.

[0077] (2) Put the uniformly mixed and fully dissolved yellow transparent solution into a water bath kettle with magnetic stirring, and use 65℃ and 900R / min conditions for stirring and heating. Heat in water bath for 65min until the transparent solution becomes a glycerol-like viscous substance. At this time, only short-chain polymer PMMA (polymethyl methacrylate) is generated in the polymer, and the carbon-carbon double bond of V4D4 is relatively stable and does not participate in the thermal polymerization reaction to generate a crosslinked macromolecular structure.

[0078] (3) Inject the viscous liquid into the mold. In this patent, square sheet-shaped polytetrafluoroethylene is used as support, and two pieces of glass are sealed to form a sheet-shaped material mold with a thickness of 1.5mm. In other embodiments, other molds can also be used to make the required polymer block materials.

[0079] (4) Put the filled mold into a constant temperature air drying oven for heating. The material is heated at 60℃ for 21h to complete the final polymerization forming. In this process, the polymerization reaction is relatively intense, and a high-sensitivity photopolymer holographic storage material is generated, which has a crosslinked macromolecular structure based on V4D4 as the crosslinking agent and a main active substance based on the unreacted vinyl group on V4D4.

[0080] (5) After the heating forming is completed, cool to room temperature, put into -3℃ refrigerator to cool for 3 min to demold, and a sheet-shaped photopolymer holographic storage material with smooth surface can be obtained.

[0081] Comparative Example 1

[0082] A preparation method of a photopolymer holographic storage material, specifically including the following steps:

[0083] ​(1) Weigh 18 g of polymerized monomer-methyl methacrylate (MMA), 0.2 g of thermal initiator-azobisisobutyronitrile (AIBN) and 0.2 g of photoinitiator phenanthraquinone (PQ) in proportion. Put the weighed raw materials into a brown reaction bottle, and perform ultrasonic oscillation at 60°C and 60HZ for 10 min to mix and dissolve the materials uniformly.

[0084] (2) Put the yellow transparent solution mixed uniformly and dissolved sufficiently into a water bath pot with magnetic stirring, and perform stirring and heating at 60°C and 900R / min. Heat in the water bath for 70 min until the transparent solution becomes a glycerol-like viscous substance.

[0085] (3) Inject the viscous liquid into a mold. In this patent, square sheet-shaped polytetrafluoroethylene is used as a support, and two pieces of glass are sealed to form a sheet material mold with a thickness of 1.5 mm. In other embodiments, other molds can also be used to form the required polymer block material.

[0086] (4) Put the filled mold into a constant-temperature air drying oven for heating. The material is heated at 60°C for 22 h to complete the final polymerization molding.

[0087] (5) After heating and molding, cool to room temperature, put into a-3°C refrigerator for 3 min for demolding, and then a sheet-shaped photopolymer holographic storage material with a smooth surface is obtained.

[0088] Test Example

[0089] Figure 3 The elution curves of polymers with different V4D4 doping concentrations in Examples 1-4 and Comparative Example 1 are shown in FIG. 1. Figure 3 In FIG. 1, the solid line is the GPC elution curve after water bath polymerization, and the molecular weight of the PMMA polymer (Comparative Example 1) is 24182 g / mol, which hardly changes compared with the result of adding V4D4, indicating that the product is only a chain polymer PMMA, and V4D4 does not participate in thermal polymerization. The hollow dot line is the elution curve of PMMA (Comparative Example 1) after baking polymerization, and the molecular weight is further increased to 109748 g / mol. The polymer with V4D4 added cannot be dissolved and cannot be tested by GPC due to crosslinking reaction, as shown in FIG. 2. Figure 4 The THF dissolution effect of polymers with different V4D4 concentrations after water bath polymerization (red label) and baking polymerization (yellow label).

[0090] Figure 5 The Raman spectra of polymers with different V4D4 doping concentrations in Examples 1-4 and Comparative Example 1 are shown in FIG. 3. Figure 5 In FIG. 3, with the addition of V4D4, the ethylene group at 1597 cm -1 The content of C=C is obtained by normalizing the peak intensity of C=O bond.Figure 5 As shown, it increased dramatically from 0 to approximately 40%.

[0091] Figure 6 Diffraction efficiency curves for different V4D4 doping concentrations were prepared for Examples 1-4 and Comparative Example 1. Figure 7 To prepare photosensitivity and saturation diffraction efficiency with different V4D4 doping concentrations for Examples 1-4 and Comparative Example 1, the following methods were used: Figure 6 and 7 It can be seen that under the exposure conditions of a single 25mW 0.5mm diameter 532nm laser with a double beam interference angle of 24°, the photosensitivity of the material is significantly improved from 0.27cm / J to 0.92cm / J (more than 3 times) and the diffraction efficiency is improved from 47.5% to 72.7% (~50%).

[0092] Figure 8 The response times and double bond contents of polymers with different V4D4 doping concentrations in Examples 1-4 and Comparative Example 1 are given. The response time can be obtained by fitting the diffraction efficiency curve. The fitting formula is as follows: With the increase of V4D4, the photoresponse time of polymer materials with C=C content gradually decreases.

[0093] Figure 9 These are holographic data storage effect images of the photopolymer holographic storage materials prepared in Example 3 and Comparative Example 1. Figure 9 It can be seen that the recording performance of V4D4-PQ / PMMA reaches its best at around 4 seconds, with a bit error rate of 4.2%, which is comparable to the performance of ordinary PQ / PMMA material recording for 8 seconds (bit error rate of 3.6%).

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the preparation of a high sensitivity photopolymer holographic storage material based on cyclotetrasiloxane, characterized in that, The method comprises the following steps: (1) uniformly mixing an acrylic ester monomer, a multi-vinyl crosslinking agent, a thermal initiator and a photo initiator to obtain a mixed solution; (2) heating the mixed solution to perform a prepolymerization reaction; (3) performing a thermal polymerization reaction on the prepolymer obtained in step (2) to obtain a high-sensitivity photopolymer holographic storage material; the multi-vinyl crosslinking agent is tetramethyl tetra-vinyl cyclosiloxane; the photo initiator is phenanthraquinone; the multi-vinyl crosslinking agent accounts for 5-15% of the mass sum of the acrylic ester monomer and the multi-vinyl crosslinking agent.

2. The method for preparing a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane according to claim 1, characterized in that, the acrylic ester monomer is any one of methyl methacrylate, ethyl acrylate or lauryl acrylate.

3. The method for preparing a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane according to claim 1, characterized in that, the thermal initiator is azobis isobutyronitrile.

4. Process for the preparation of a high-sensitivity photopolymer holographic storage material based on cyclotetrasiloxane according to any one of claims 1 to 3, characterized in that, both the thermal initiator and the photo initiator account for 0.5-2% of the mass sum of the acrylic ester monomer and the multi-vinyl crosslinking agent.

5. The method for preparing a high-sensitivity photopolymer holographic recording material based on cyclotetrasiloxane according to claim 1, characterized in that, the prepolymerization reaction is performed at a temperature of 60-70℃ for 60-70 min under stirring.

6. The method for preparing a high-sensitivity photopolymer holographic recording material based on cyclotetrasiloxane according to claim 1, characterized in that, the thermal polymerization reaction is performed at a temperature of 60-65℃ for 20-22 h.

7. The method for preparing a high-sensitivity photopolymer holographic recording material based on cyclotetrasiloxane according to claim 6, characterized in that, in step (3), the prepolymer obtained in step (2) is poured into a mold to be sealed, and then the thermal polymerization reaction is performed, after which the mold is demolded.

8. The high-sensitivity photopolymer holographic storage material prepared by the method of any one of claims 1-7.

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