Preparation method of photochromic transparent wood with high sensitivity to sunlight

Abstract

The present invention provides a method for preparing photochromic transparent wood with high sensitivity to sunlight; we applied a new and simple synthesis method, which is based on removing light-absorbing lignin from natural wood. First, a sheet-shaped wood sample with uniform thickness is pretreated, and then the lignin is removed by treatment with sodium chlorite solution and glacial acetic acid. Then, it is ultrasonically treated with distilled water until neutral to obtain a wood sample with the lignin component removed; the sample is dehydrated by ultrasonic solvent replacement using absolute ethanol, isopropyl acetate, and propylene oxide to further obtain a dehydrated wood sample with the lignin component removed; then, we mix a sunlight-color-changing material (OP), prepolymerized methyl methacrylate (PMMA), and polyacrylic acid (PDESP) and directly incorporate them into the delignified wood, and finally cure and polymerize. The present invention has developed for the first time a photochromic transparent wood with high sensitivity to sunlight. The obtained reversible photochromic transparent wood can change from colorless to red rapidly under sunlight in only 1.5 seconds, and can change from red to colorless rapidly in the dark or under visible light in only 2 seconds.

Description

Technical Field

[0001] The invention belongs to the field of new wood technology development and modification, and specifically relates to a method for preparing photochromic transparent wood with high sensitivity to sunlight. Background Art

[0002] At present, a few domestic and foreign scholars have conducted research on transparent wood. The most prominent application is to use it as a building material, which is expected to replace traditional lighting materials such as glass. It can not only provide continuous and effective lighting, but also form natural and comfortable indoor lighting. In addition, transparent wood has good thermal insulation properties, which can greatly reduce the use of refrigeration and heating equipment to save electricity.

[0003] Transparent wood is a new type of wood-based composite material made of natural wood and various polymers. It has unique optical properties of high transparency and high haze while maintaining the high mechanical strength of native wood. By filling different functional materials, transparent wood can also be given functional properties such as photochromism, which has become a hot research direction for high-value utilization of wood in recent years. Light-responsive color-changing transparent wood has unique optical and mechanical properties and has great development prospects in optoelectronic devices, energy-saving building materials, safety signs, and biomedicine. However, as a new material that is in the ascendant, there is still a certain gap between it and large-scale production and application.

[0004] There are few articles or reports on the photochromic functional modification of transparent wood at home and abroad. Transparent wood is endowed with photochromic properties by doping the sunlight-chromic material OP powder into transparent wood composites. Light or visible light / darkness can trigger a reversible light switch, corresponding to the two structures of OP. Under sunlight, the carbon-oxygen (C–O) bond of the spiropyran structure will be broken due to the electron transition from the nitrogen atom to the oxygen atom between the ring structures of the spiropyran molecules, resulting in a transition from a ring-closed to a ring-open structure. In contrast, under visible light / darkness, the C–O bond is connected due to the electron transition from the oxygen atom to the nitrogen atom, which results in a transition from an open-ring structure to a closed-ring structure. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing photochromic transparent wood with high sensitivity to sunlight, optimize the impregnation process for preparing transparent wood, endow the wood with high-sensitivity photochromic properties, select sunlight-chromic material OP powder as the sensing system of sunlight, and successfully prepare photochromic transparent wood with high sensitivity to sunlight. The photochromic transparent wood prepared in this study does not contain any metal materials, is an environmentally friendly, energy-saving, and highly light-sensitive solid-state lighting material, and has great application value in energy-saving materials such as smart windows.

[0006] The present invention provides a method for preparing photochromic transparent wood with high sensitivity to sunlight, comprising the following steps:

[0007] 1) Select a sheet of wood sample with uniform thickness, put it into distilled water at room temperature to fully wet it, and set it aside;

[0008] 2) placing the sample fully moistened in step 1) in an oven at 50-60° C. for pretreatment for 1-2 hours, and then drying it in an oven at 100° C. for 3-5 hours;

[0009] 3) placing the sample after treatment in step 2) into a well-stirred sodium chlorite solution having a mass fraction of 4%-6%, and adjusting the pH of the mixed solution to 4-5 using acetic acid, and then heating the mixed solution in a water bath at 80° C. for 3-6 hours to remove lignin until the flaky wood sample appears white;

[0010] 4) treating the sample obtained in step 3) with distilled water to neutrality by ultrasonic treatment, and then dehydrating the sample by ultrasonic solvent displacement method using a gradient ratio of anhydrous ethanol, isopropyl acetate and propylene oxide mixed solution to further obtain a dehydrated flaky wood sample with lignin components removed, and immersing the sample in anhydrous ethanol until use in the next step;

[0011] 5) prepolymerizing methyl methacrylate and thermal initiator azobisisobutyronitrile at 75° C. at a suitable stirring speed until the mixture is an oily PMMA mixed solution, and then cooling the mixture to room temperature and mixing it with 0.03wt%-0.05wt% of OP powder until the OP powder is completely dissolved in the oily PMMA solution;

[0012] 6) chloroform and acrylic acid are mixed in a molar ratio of 1:3-1:5 to obtain PDES, and the PDES is fully mixed with a cross-linking agent PEG and a photoinitiator 2959 in a mass ratio of 100:3.5:1 to obtain a PDESP solution;

[0013] 7) fully mixing the PDESP solution obtained in step 6) and the oily PMMA solution obtained in step 5) at a mass ratio of 1:5 to 1:8;

[0014] 8) Immersing the flaky wood sample obtained in step 4) with the lignin component removed into the solution obtained in step 7) and placing it in a vacuum glass sealed tube, and immersing it multiple times using an ultra-vacuum high-frequency ultrasonic method to achieve complete immersion.

[0015] 9) To prevent the volume shrinkage during the monomer polymerization from affecting the formation of transparent wood, the sheet wood sample with the lignin component removed is fully impregnated with PMMA, and the sample obtained in step 8) is placed in a silica gel mold of appropriate size. Then, a certain amount of PMMA mixed solution is used to coat the surface for curing, and it is left at room temperature for 15 - 18 hours to obtain a photochromic transparent wood with high sensitivity to sunlight;

[0016] 2. The sheet wood sample in step 1) is poplar wood, which is prepared using the cross-section.

[0017] 3. The pretreatment temperature in step 2) is 50 - 60 °C, and it needs to be dried at 100 °C before proceeding to the next step.

[0018] 4. The concentration of the sodium chlorite solution used to remove lignin in step 3) is 4% - 6%, the pH of the sodium chlorite solution is adjusted to 4 - 5 using acetic acid, and the temperature and time for removing lignin from the sheet wood sample by water bath heating are 80 °C and 3 - 6 hours respectively.

[0019] 5. In step 4), the delignified wood chips need to be treated with water until neutral, and then the sample is dehydrated using a mixed solution of anhydrous ethanol, isopropyl acetate, and propylene oxide with a gradient ratio by ultrasonic solvent replacement method.

[0020] 6. In step 5), the dosage ratio of methyl methacrylate to azobisisobutyronitrile is 15 mL: 0.1 g - 0.13 g, and the mass fraction of the OP powder used relative to PMMA is 0.03 wt% - 0.05 wt%.

[0021] 7. In step 6), chloroform and acrylic acid are mixed in a molar ratio of 1:3 - 1:5, and are fully mixed with the cross-linking agent PEG and the photoinitiator 2959 in a mass ratio of 100:3.5:1 to obtain the PDESP solution

[0022] 8. In step 7), the PDESP solution obtained in step 6) and the oily PMMA solution obtained in step 5) are fully mixed in a mass ratio of 1:5 - 1:8;

[0023] 9. The impregnation method in step 8) is multiple ultra-high vacuum high-frequency ultrasonic impregnation in an ultra-high vacuum glass sealed tube, and in step 9), curing is carried out by placing it in a silica gel template of appropriate size at room temperature for 15 - 18 hours.

[0024] 10. A preparation method of any of the above-mentioned photochromic transparent woods with high sensitivity to sunlight.

[0025] The beneficial effects of the present invention are:

[0026] 1) The present invention develops a switchable photochromic transparent wood that is highly sensitive to sunlight.

[0027] 2) The photochromic transparent wood composite material obtained by the present invention not only retains the layered porous structure of wood, but also has aesthetic properties (such as plastic aesthetic patterns), excellent optical properties, and reliable thermal insulation properties.

[0028] 3) This SPTW exhibits a fast and switchable photochromic response to sunlight and ideal cycling stability, maintaining its original photochromic effect even after multiple cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram of the photochromic transparent wood production in the embodiment.

[0030] Figure 2 The color change and response time of the photochromic transparent wood in the embodiment before and after illumination.

[0031] Figure 3 This is a scanning electron microscope (SEM) image of the photochromic transparent wood after preparation in the embodiment.

[0032] Figure 4 The thermogravimetric analysis (TGA) diagram of the photochromic transparent wood in the examples. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments.

[0034] Embodiment 1:

[0035] 1) Select a sheet of wood sample with uniform thickness, put it into distilled water at room temperature to fully wet it, and set it aside;

[0036] 2) placing the sample fully moistened in step 1) in an oven at 50-60° C. for pretreatment for 1-2 hours, and then drying it in an oven at 100° C. for 3-5 hours;

[0037] 3) placing the sample after treatment in step 2) into a well-stirred sodium chlorite solution having a mass fraction of 4%-6%, and adjusting the pH of the mixed solution to 4-5 using acetic acid, and then heating the mixed solution in a water bath at 80° C. for 3-6 hours to remove lignin until the flaky wood sample appears white;

[0038] 4) The sample obtained from step 3) is ultrasonically treated with distilled water until neutral, and then dehydrated by ultrasonic solvent replacement using a mixed solution of anhydrous ethanol, isopropyl acetate, and propylene oxide with a gradient ratio to further obtain a dehydrated lignin - removed flaky wood sample. The sample is immersed in anhydrous ethanol until the next use;

[0039] 5) Methyl methacrylate and the thermal initiator azobisisobutyronitrile are pre - polymerized at 75 °C with a suitable stirring speed until an oily PMMA mixed solution is formed. Then the obtained mixture is cooled to room temperature and mixed with 0.03 wt% - 0.05 wt% of OP powder until the OP powder is completely dissolved in the oily PMMA solution;

[0040] 6) Trichloromethane and acrylic acid are mixed in a molar ratio of 1:3 - 1:5 to obtain PDES, and are fully mixed with the cross - linker PEG and the photo - initiator 2959 in a mass ratio of 100:3.5:1 to obtain a PDESP solution;

[0041] 7) The PDESP solution obtained in step 6) and the oily PMMA solution obtained in step 5) are fully mixed in a mass ratio of 1:5 - 1:8;

[0042] 8) The lignin - removed flaky wood sample obtained in step 4) is immersed in the solution obtained in step 7) and placed in a vacuum glass - sealed tube, and is impregnated multiple times by the method of ultra - vacuum high - frequency ultrasound to achieve complete impregnation.

[0043] 9) To prevent the volume shrinkage during monomer polymerization from affecting the formation of transparent wood, the lignin - removed flaky wood sample is fully impregnated with PMMA, and the sample obtained in step 8) is placed in a silicone mold with a suitable size. Then, a certain amount of PMMA mixed solution is used to coat the surface for curing, and it is left at room temperature for 15 - 18 hours to obtain a photochromic transparent wood with high sensitivity to sunlight.

Claims

1. A preparation method of photochromic transparent wood with high sensitivity to sunlight, characterized in that, The following steps are involved: 1) Select a sheet of wood sample with uniform thickness, put it into distilled water at room temperature to fully wet it, and set it aside; 2) placing the sample fully moistened in step 1) in an oven at 50-60° C. for pretreatment for 1-2 hours, and then drying it in an oven at 100° C. for 3-5 hours; 3) placing the sample after treatment in step 2) into a well-stirred sodium chlorite solution having a mass fraction of 4%-6%, and adjusting the pH of the mixed solution to 4-5 using acetic acid, and then heating the mixed solution in a water bath at 80° C. for 3-6 hours to remove lignin until the flaky wood sample appears white; 4) treating the sample obtained in step 3) with distilled water to neutrality by ultrasonic treatment, and then dehydrating the sample by ultrasonic solvent displacement method using a gradient ratio of anhydrous ethanol, isopropyl acetate and propylene oxide mixed solution to further obtain a dehydrated flaky wood sample with lignin components removed, and immersing the sample in anhydrous ethanol until use in the next step; 5) prepolymerizing methyl methacrylate and thermal initiator azobisisobutyronitrile at 75° C. at a suitable stirring speed until the mixture is an oily PMMA mixed solution, and then cooling the mixture to room temperature and mixing it with 0.03wt%-0.05wt% of OP powder until the OP powder is completely dissolved in the oily PMMA solution; 6) chloroform and acrylic acid are mixed in a molar ratio of 1:3-1:5 to obtain PDES, and the PDES is fully mixed with a cross-linking agent PEG and a photoinitiator 2959 in a mass ratio of 100:3.5:1 to obtain a PDESP solution; 7) fully mixing the PDESP solution obtained in step 6) and the oily PMMA solution obtained in step 5) at a mass ratio of 1:5 to 1:8; 8) immersing the flaky wood sample obtained in step 4) with the lignin component removed into the solution obtained in step 7) and placing the sample in a vacuum glass sealed tube, and immersing the sample multiple times using an ultra-vacuum high-frequency ultrasonic method to achieve complete immersion; 9) In order to prevent the volume shrinkage during the polymerization of the monomer from affecting the formation of transparent wood, the flaky wood sample from which the lignin component has been removed is fully impregnated with PMMA, and the sample obtained in step 8) is placed in a silicone mold of appropriate size, and then the surface is coated with a certain amount of PMMA mixed solution for curing, and placed at room temperature for 15-18 hours to obtain photochromic transparent wood with high sensitivity to sunlight.

2. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that, The sheet-like wood sample in step 1) is poplar, which is prepared by using a cross section.

3. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that, The pretreatment temperature in step 2) is 50-60°C and the product needs to be dried at 100°C before proceeding to the next step.

4. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that, In the step 3), the concentration of the sodium chlorite solution used to remove lignin is 4%-6%, the pH value of the sodium chlorite solution is adjusted to 4-5 using acetic acid, and the temperature and time for heating the flaky wood sample in a water bath to remove lignin are 80° C. and 3-6 hours, respectively.

5. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that, In the step 4), the delignified wood chips are first treated with water to neutralize, and then the samples are dehydrated by ultrasonic solvent replacement using a mixed solution of anhydrous ethanol, isopropyl acetate and propylene oxide in a gradient ratio.

6. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that, In step 5), the dosage ratio of methyl methacrylate to azobisisobutyronitrile is 15 mL: 0.1 g to 0.13 g, and the mass fraction of the OP powder used is 0.03 wt%-0.05 wt% relative to PMMA.

7. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that In step 6), chloroform and acrylic acid are mixed at a molar ratio of 1:3-1:5, and are fully mixed with the crosslinking agent PEG and the photoinitiator 2959 at a mass ratio of 100:3.5:1 to obtain the PDESP solution.

8. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that In step 7), the PDESP solution obtained in step 6) and the oily PMMA solution obtained in step 5) are fully mixed at a mass ratio of 1:5-1:

8.

9. The preparation method of a photochromic transparent wood with high sensitivity to sunlight according to claim 1, characterized in that, The impregnation method in step 8) is multiple ultra-high vacuum high-frequency ultrasonic impregnation in an ultra-high vacuum glass sealed tube, and in step 9), a silica gel template with a suitable size is placed at room temperature for 15-18 hours for curing.

10. A method for preparing a photochromic transparent wood with high sensitivity to sunlight as described in any one of claims 1-9.

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