A vanillin-based tetraene monomer with an acetal structure, its preparation and application

Abstract

This invention discloses a vanillin-based acetal-containing tetraene monomer, its preparation, and its applications. As shown in Figure 1 of the specification, the vanillin-based acetal-containing tetraene monomer of this invention is prepared from vanillin, which is widely available, renewable, and environmentally friendly. Furthermore, it contains an acetal structure, resulting in biodegradable polymers during thermosetting. In addition, the vanillin-based acetal-containing tetraene monomer of this invention has multiple sets of terminal double bonds, leading to high crosslinking degree, good mechanical properties, high glass transition temperature, and good light transmittance after preparing thermosetting polymers via click reaction.

Description

Technical Field

[0001] This invention belongs to the field of chemistry, and in particular relates to a vanillin-based tetraene monomer containing an acetal structure, its preparation, and its application. Background Technology

[0002] Thermosetting polymers possess excellent thermal and mechanical properties and have important applications in various fields. Currently, commercially available thermosetting materials mainly use non-renewable petroleum-based monomers as raw materials, and their three-dimensional cross-linked network structure makes them difficult to reprocess or recycle once formed. Therefore, the preparation of biodegradable thermosetting polymers using renewable resources as raw materials has attracted much attention.

[0003] Biomass resources are the most abundant renewable resources, but due to the special structural characteristics of biomass, direct modification of it cannot obtain high-performance bio-based polymer materials. However, we can isolate bio-based monomers from these biomass resources that have chemical structures similar to petroleum-based monomers, such as vanillin, eugenol, guaiacol, and levulinic acid.

[0004] Currently, vanillin has been industrially produced using lignin as a raw material. It has a variety of functional groups, including aldehyde groups, phenolic hydroxyl groups, and benzene rings. Therefore, chemical modification based on the structure of vanillin can yield a series of vanillin-based functional monomers, providing a basis for the preparation of vanillin-based polymers.

[0005] Literature reports that vanillin is used to obtain vanillin-based diene monomers containing carboxylic acid ester structures through etherification and tris(t)- ...

[0006] Although the aforementioned bio-based thermosetting polymers are prepared using vanillin as a raw material and have biodegradable properties, they suffer from problems such as stringent polymerization conditions and difficulty in adjusting material properties. In particular, their light transmittance and mechanical properties are poor, which severely limits their application in some transparent films. Summary of the Invention

[0007] The purpose of this invention is to provide a vanillin-based acetal-containing tetraene monomer, its preparation, and its application. The vanillin-based acetal-containing tetraene monomer of this invention is prepared from vanillin, which is widely available, renewable, and environmentally friendly. Furthermore, it contains an acetal structure, resulting in biodegradable thermosetting polymers. In addition, the vanillin-based acetal-containing tetraene monomer of this invention has multiple sets of terminal double bonds, leading to high crosslinking degree, good mechanical properties, high glass transition temperature, and good light transmittance after preparing thermosetting polymers via click reaction.

[0008] The technical solution of this invention: A vanillin-based tetraene monomer containing an acetal structure, the chemical structural formula of which is shown below:

[0009]

[0010] Where n = 1 - 8.

[0011] A method for preparing the aforementioned vanillin-based acetal-containing tetraene monomer includes the following steps:

[0012] (1) Allyl vanillin was prepared by allyl etherification reaction using vanillin and allyl bromide as raw materials in an organic solvent with an inorganic base as a catalyst.

[0013] (2) Allyl vanillin was subjected to the Claisen rearrangement reaction under inert gas protection to obtain the rearranged product.

[0014] (3) Using rearrangement products and haloolefins as raw materials, vanillin-based diene monomers are prepared by allyl etherification reaction in an organic solvent with an inorganic base as a catalyst.

[0015] (4) Using p-toluenesulfonic acid as a catalyst, vanillin-based diene monomer and pentaerythritol as raw materials, vanillin-based acetal tetraene monomer was prepared by acetal reaction.

[0016] In a further embodiment, the preparation method of the aforementioned vanillin-based acetal-containing tetraene monomer, in step (1), the molar ratio of vanillin to allyl bromide is 1:1-2; the organic solvent is one or a mixture of any of methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, or dimethyl sulfoxide; the inorganic base catalyst is one or a mixture of any of K2CO3, Cs2CO3, KI, or NaI, and the amount used is 0.5-2 times the molar amount of vanillin; the reaction temperature is 50-150℃, and the reaction time is 1-48h.

[0017] In a further embodiment, the preparation method of the aforementioned vanillin-based acetal-containing tetraene monomer, in step (2), the inert gas is one of nitrogen, argon or helium, the reaction temperature is 180-240℃, and the reaction time is 1-24h.

[0018] In a further embodiment, the method for preparing the aforementioned vanillin-based acetal-containing tetraene monomer, the halogenated olefin structure described in step (3) is as follows:

[0019]

[0020] Where n = 0-7, and X is a bromine atom or a chlorine atom.

[0021] In a further embodiment, the preparation method of the aforementioned vanillin-based acetal-containing tetraene monomer, in step (3), the molar ratio of the rearranged product to the haloalkene is 1:1-2; the organic solvent is one or a mixture of any of methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide or dimethyl sulfoxide; the inorganic base catalyst is one or a mixture of any of K2CO3, Cs2CO3, KI or NaI, and the amount used is 0.5-2 times the molar amount of vanillin; the reaction temperature is 50-150℃, and the reaction time is 1-48h.

[0022] A vanillin-based thermosetting polymer containing an acetal structure is prepared by using the vanillin-based acetal-based tetraene monomer of claim 1 as a raw material and undergoing mercapto-olefin click polymerization with thiol monomers of different functionalities.

[0023] In a further embodiment, the aforementioned vanillin-based thermosetting polymer containing an acetal structure, wherein the thiol monomer is one or any combination of 1,2-ethanedithiol, 1,3-propanedithiol, 1,6-hexanedithiol, 1,10-decanedithiol, bis(3-mercaptopropionic acid) ethylene glycol, trimethylolpropane tris(3-mercaptopropionate) or tetra(3-mercaptopropionate pentaerythritol ester).

[0024] In a further embodiment, the aforementioned vanillin-based acetal-containing thermosetting polymer is prepared by: first melting the vanillin-based acetal-containing tetraene monomer at 90-120°C, adding a thiol monomer, then adding 0.5-3 wt% of photoinitiator 1173 or 2,2-dimethoxy-2-phenylacetophenone, stirring evenly, curing under a UV lamp for 10-30 min, and then heat curing at 70-140°C for 0.5-12 h.

[0025] In a further embodiment, the aforementioned vanillin-based acetal-containing thermosetting polymer is formulated such that the ratio of the vanillin-based acetal-containing tetraene monomer to the thiol monomer is 1:1, based on the molar ratio of the C=C double bond in the vanillin-based acetal-containing tetraene monomer to the -SH functional group in the thiol monomer.

[0026] Beneficial effects of the present invention

[0027] 1. The vanillin-based acetal tetraene monomer of the present invention is prepared from vanillin, which has the advantages of wide availability, renewability, and environmental friendliness.

[0028] 2. The vanillin-based acetal-containing tetraene monomer of the present invention contains an acetal structure, which gives the polymer the advantage of being biodegradable when preparing thermosetting polymers.

[0029] 3. The vanillin-based acetal-containing tetraene monomer of the present invention has multiple sets of terminal double bonds. After preparing thermosetting polymers through click reaction, it has the characteristics of high crosslinking degree, good mechanical properties, high glass transition temperature and good light transmittance, and has good application prospects in transparent films. Attached Figure Description

[0030] Appendix Figure 1 This is the chemical structural formula of the vanillin-based tetraene monomer containing an acetal structure according to the present invention;

[0031] Appendix Figure 2 The hydrogen spectrum of the monomer obtained in Example 1;

[0032] Appendix Figure 3 The carbon spectrum of the monomer obtained in Example 1;

[0033] Appendix Figure 4 The hydrogen spectrum of the monomer obtained in Example 2;

[0034] Appendix Figure 5 The carbon spectrum of the monomer obtained in Example 2;

[0035] Appendix Figure 6 The hydrogen spectrum of the monomer obtained in Example 3;

[0036] Appendix Figure 7 The carbon spectrum of the monomer obtained in Example 3;

[0037] Appendix Figure 8 The hydrogen spectrum of the monomer obtained in Example 4;

[0038] Appendix Figure 9 The carbon spectrum of the monomer obtained in Example 4;

[0039] Appendix Figure 10 DSC and TGA analyses were performed on the samples prepared in Example 5;

[0040] Appendix Figure 11 DSC and TGA analyses were performed on the samples prepared in Example 6;

[0041] Appendix Figure 12 Mechanical property analysis of the samples prepared in Examples 5 and 6;

[0042] Appendix Figure 13 The degradation status of the sample in Example 8 is shown. Detailed Implementation

[0043] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0044] Embodiments of the present invention

[0045] Example 1

[0046] The allylation reaction of vanillin monomer is shown in the following equation:

[0047]

[0048] Procedure: 90 g of vanillin was added to a 1 L flask, and dissolved in an appropriate amount of anhydrous ethanol at 40 °C. 81.75 g of anhydrous potassium carbonate was added and stirred for 15 min. 80.32 g of allyl bromide was added dropwise using a dropping funnel. The mixture was heated to 80 °C, refluxed, and reacted for 24 h. The anhydrous potassium carbonate was removed by suction filtration, the mixture was rotary evaporated, diluted with pure water, and the organic phase was extracted with ethyl acetate. The phase was washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and dried to obtain 105 g of a pale yellow liquid, with a yield of 92.34%.

[0049] 1 HNMR(400MHz,DMSO-d6),δ(ppm):9.84(s,1H,-CHO),7.65–7.05(m,3H,aromaticproton s), 6.19–5.95(m,1H,-CH=), 5.38(m,2H,=CH2-), 4.68(m,2H,-CH2-), 3.84(s,3H,-CH3). 13 CNMR(101MHz,DMSO-d6)δ(ppm):191.91,153.49,149.79,133.55,130.21,126.48,118.76,112.88,110.06,69.49,56.02,39.99.

[0050] Example 2

[0051] The rearrangement reaction of allylated vanillin is shown in the following equation:

[0052]

[0053] Procedure: Weigh 105 g of allylvanillin (4-allyloxy-3-methoxybenzaldehyde) from Example 1 into a 500 mL two-necked round-bottom flask and react at 205 °C for 3.5 h under a nitrogen atmosphere. After the reaction is complete, pour the mixture into a beaker while hot and recrystallize it with n-hexane to obtain 81.9 g of yellow crystals, yield 78.00%, melting point: 80.6 °C.

[0054] 1 HNMR(400MHz,DMSO-d6)δ(ppm):9.86(s,1H,-OH),9.76(s,1H,-CHO),7.32(s,2H,aromatic protons),5.94(s,1H,-CH=),5.05(s,2H,=CH2-),3.88(s,3H,-OCH3),3.35(m,2H,-CH2-). 13 CNMR(100MHz,DMSO-d6)δ(ppm):192.06,151.17,148.61,137.15,128.88,127.58,126.97,116.91,109.82,56.86,40.45,34.30.

[0055] Example 3

[0056] The etherification reaction equation for the rearrangement product is as follows:

[0057]

[0058] Procedure: Weigh 81.9 g of 3-allyl-4-hydroxy-5-methoxybenzaldehyde from Example 2 into a 1000 mL two-necked flask, add 300 mL of anhydrous ethanol, transfer to an oil bath at 80 °C to dissolve, and then add 65.00 g of anhydrous potassium carbonate. Add 56.77 g of bromopropene dropwise using a dropper, then heat to 80 °C and reflux for 24 h before stopping the reaction. Filter to remove salt, extract with a small amount of water and ethyl acetate, wash with saturated brine, collect the organic phase, remove excess bromopropene, ethyl acetate, and ethanol by rotary evaporation, and purify by column chromatography to obtain 95 g of a pale yellow liquid product, with a yield of 95.98%.

[0059] 1HNMR(400MHz, CDCl3)δ(ppm):9.87(s,1H,-CHO),7.33(s,2H,aromaticprotons),6.19–5.83(m,2 H,-CH=),5.49–4.99(m,4H,=CH2-),4.60(m,2H,-CH2-),3.92(s,3H,-OCH3),3.48(s,2H,-CH2-). 13 CNMR(101MHz,CDCl3)δ(ppm):191.41,153.26,151.30,136.34,134.55,133 .89,132.29,126.55,117.96,116.47,108.92,77.29,73.89,55.88,34.24.

[0060] Example 4

[0061] The synthesis of tetraallyl-terminated acetal bio-based monomers is shown in the following reaction equation:

[0062]

[0063] Procedure: In a 1L single-necked flask, add 99g of 3-allyl-4-allyloxy-5-methoxybenzaldehyde and 29g of pentaerythritol (from Example 3). Add 500mL of isopropanol and 4.3mmol of p-toluenesulfonic acid, and stir at room temperature for 24h. Remove isopropanol by rotary evaporation, and wash with 200mL of 3wt% NaHCO3 and pure water. Dry under vacuum by column chromatography with ethyl acetate / petroleum ether (1:6) to give 80g of a yellow transparent liquid, yield 65.89%, melting point: 76.29℃.

[0064] 1 HNMR(400MHz, CDCl3)δ(ppm):6.94-6.90(S,4H,aromaticprotons),6.00(m,4H,-CH=),5.39(s,2H,-CHOO),5.33-5.06(m,8H,=CH 2-),4.87(s,2H,-CH2O-),4.46(m,4H,-CH2-),3.86(s,6H,-OCH3),3.81(s,2H,-CH2O-),3.65(s,2H,-CH2O-),3.43(s,4H,-CH2-). 13CNMR(101MHz,CDCl3)δ(ppm):152.82,146.45,137.07,134.41,134.04,133.60,119.8 8,117.42,115.89,108.06,102.29,77.17,73.82,71.17,70.67,55.84,34.40,32.59.

[0065] Example 5

[0066] Steps: The vanillin-based acetal-containing tetraene monomer (6g) from Example 4 was completely melted at 100°C. A certain amount of dithiol monomer and 2wt% of 2,2-dimethoxy-2-phenylacetophenone were added and stirred evenly. The mixture was poured into a glass petri dish and crosslinked under a UV lamp with a wavelength of 365nm for 10min. Then, it was heat-cured in an oven at 70°C for 30min to obtain a light yellow transparent film.

[0067] Table 1 Thermal properties of the thermosetting materials prepared in Example 5

[0068]

[0069] Table 2 Mechanical properties of thermosetting materials obtained in Example 5

[0070]

[0071] Example 6

[0072] Steps: The vanillin-based acetal-containing tetraene monomer (6g) from Example 4 was completely melted at 100°C. A certain amount of multifunctional thiol monomer and 2wt% of 2,2-dimethoxy-2-phenylacetophenone were added and stirred evenly. The mixture was poured into a glass petri dish and crosslinked under a UV lamp with a wavelength of 365nm for 20min. Then, it was heat-cured in an oven at 120°C for 6h to obtain a light yellow transparent film.

[0073] Table 3 Thermal properties of the thermosetting materials prepared in Example 6

[0074]

[0075] Table 4 Mechanical properties of the thermosetting materials prepared in Example 6

[0076]

[0077] Example 7

[0078] Steps: The vanillin-based acetal-containing tetraene monomer (6g) from Example 4 was completely melted at 100°C. 1,2-ethylenedithiol (ET) and pentaerythritol tetrakis(3-mercaptopropionate) (PETM) were added in different proportions. 2wt% of 2,2-dimethoxy-2-phenylacetophenone was added and stirred until homogeneous. The mixture was poured into a glass petri dish and crosslinked under a 365nm UV lamp for 30 min. Subsequently, it was heat-cured in an oven at 140°C for 12 h to obtain a pale yellow transparent film.

[0079] Table 5 Thermal properties of the thermosetting materials prepared in Example 7

[0080]

[0081] Table 6 Mechanical properties of the thermosetting materials prepared in Example 7

[0082]

[0083] Example 8

[0084] The films P1a2d, P1a2e, and P1a2f prepared in Example 6 were placed in a 3 mol / L HCl aqueous solution and subjected to degradation experiments at 70°C. The results showed that the film materials were completely degraded after soaking for 4 hours.

[0085] Example 9

[0086] Vanillin monomer allylation reaction:

[0087] Vanillin was added to a 1L flask and dissolved in methanol. Then, KI (0.5 molar amounts of vanillin) was added and stirred. Allyl bromide was added dropwise using a dropping funnel at a molar ratio of vanillin to allyl bromide of 1:1. The mixture was heated to 50°C, refluxed, and reacted for 48 hours. The KI was removed by suction filtration, the mixture was rotary evaporated, diluted with pure water, and the organic phase was extracted with ethyl acetate. The mixture was washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and dried to obtain a pale yellow liquid.

[0088] Example 10

[0089] Vanillin monomer allylation reaction:

[0090] Vanillin was added to a 1L flask and dissolved in N,N-dimethylacetamide. Then, 0.5 molar amounts of Cs₂CO₃ were added to the flask and stirred. Allyl bromide was added dropwise using a dropping funnel at a molar ratio of vanillin to allyl bromide of 1:2. The mixture was heated to 150°C, refluxed, and reacted for 1 hour. The Cs₂CO₃ was removed by suction filtration, the mixture was rotary evaporated, diluted with pure water, and the organic phase was extracted with ethyl acetate. The mixture was washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and dried to obtain a pale yellow liquid.

[0091] Example 11

[0092] The rearrangement reaction of allyl vanillin:

[0093] Procedure: Weigh allyl vanillin (4-allyloxy-3-methoxybenzaldehyde) from Example 1 into a two-necked round-bottom flask, and react at 180°C for 24 hours under an argon atmosphere. After the reaction is complete, pour the mixture into a beaker while still hot, and recrystallize it with n-hexane to obtain yellow crystals.

[0094] Example 12

[0095] The rearrangement reaction of allyl vanillin:

[0096] Procedure: Weigh allyl vanillin (4-allyloxy-3-methoxybenzaldehyde) from Example 1 into a two-necked round-bottom flask, and react at 240°C for 1 hour under a helium atmosphere. After the reaction is complete, pour the mixture into a beaker while still hot, and recrystallize it with n-hexane to obtain yellow crystals.

[0097] Example 13

[0098] Etherification reaction of rearrangement products:

[0099] Procedure: Weigh 3-allyl-4-hydroxy-5-methoxybenzaldehyde from Example 2 into a 1000 mL two-necked flask, add methanol, and dissolve in an oil bath at 80°C. Then add 0.5 molar amounts of Cs₂CO₃ to vanillin. Add bromopropene dropwise using a dropper, with a molar ratio of bromopropene to 3-allyl-4-hydroxy-5-methoxybenzaldehyde of 1:2. The temperature is then raised to 50°C, and the reaction is refluxed for 48 h before stopping. Filter to remove salt, extract with a small amount of water and ethyl acetate, wash with saturated brine, collect the organic phase, remove excess bromopropene, ethyl acetate, and ethanol by rotary evaporation, and purify by column chromatography to obtain a pale yellow liquid product.

[0100] Example 14

[0101] Etherification reaction of rearrangement products:

[0102] Procedure: Weigh 3-allyl-4-hydroxy-5-methoxybenzaldehyde from Example 2 into a two-necked flask, add dimethyl sulfoxide, and dissolve in an oil bath at 80°C. Then add NaI at twice the molar volume of vanillin. Add bromopropene dropwise using a dropper, with a molar ratio of bromopropene to 3-allyl-4-hydroxy-5-methoxybenzaldehyde of 1:1. The temperature is then raised to 150°C, and the reaction is stopped after reflux for 1 hour. Filter to remove salt, extract with a small amount of water and ethyl acetate, wash with saturated brine, collect the organic phase, remove excess bromopropene, ethyl acetate, and ethanol by rotary evaporation, and purify by column chromatography to obtain a pale yellow liquid product.

[0103] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A vanillin-based tetraen monomer containing an acetal structure, characterized in that, The chemical structural formula is shown as follows: ； Wherein, n=1-8.

2. A process for the preparation of a vanillyl-based hemiacetal-structured tetraene monomer according to claim 1, characterized by, Comprise the following steps: (1) with vanillin and allyl bromide as raw material, in organic solvent with inorganic base as catalyst, allyl etherification reaction preparation allyl vanillin; (2) take allyl vanillin, under inert gas protection, claisen rearrangement reaction, get rearrangement product; (3) with rearrangement product and halogenated olefin as raw material, in organic solvent with inorganic base as catalyst, allyl etherification reaction preparation vanillin based diene monomer; (4) with p-toluene sulfonic acid as catalyst, vanillin based diene monomer and pentaerythritol as raw material, through acetal reaction preparation obtain vanillin based acetal structure four alkene monomer.

3. The method for preparing a vanillin-based acetal-containing tetraene monomer according to claim 2, characterized in that: The molar ratio of vanillin to allyl bromide in step (1) is 1:1-2; the organic solvent is one or a mixture of any of methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide or dimethyl sulfoxide; the inorganic base catalyst is one or a mixture of any of K2CO3, Cs2CO3, KI or NaI, and the amount used is 0.5-2 times the molar amount of vanillin; the reaction temperature is 50-150 DEG C, and the reaction time is 1-48 h.

4. The method for preparing a vanillin-based acetal-containing tetraene monomer according to claim 2, characterized in that: The inert gas in step (2) is one of nitrogen, argon or helium, the reaction temperature is 180-240 DEG C, and the reaction time is 1-24 h.

5. The method for preparing a vanillin-based acetal-containing tetraene monomer according to claim 2, characterized in that, The halogenated olefin in step (3) has the following structural formula: ； Wherein, n=0-7, X is bromine atom or chlorine atom.

6. The method for preparing a vanillin-based acetal-containing tetraene monomer according to claim 2, characterized in that: The molar ratio of rearrangement product to halogenated olefin in step (3) is 1:1-2; the organic solvent is one or a mixture of any of methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide or dimethyl sulfoxide; the inorganic base catalyst is one or a mixture of any of K2CO3, Cs2CO3, KI or NaI, and the amount used is 0.5-2 times the molar amount of vanillin; the reaction temperature is 50-150 DEG C, and the reaction time is 1-48 h.

7. A vanillal-based acetal-containing thermoset polymer characterized by: The vanillin based acetal structure four alkene monomer of claim 1 is used as raw material, and a thiol monomer with different functionality is used to prepare a thiol-ene click polymer through thiol-ene click polymerization; The thiol monomer is one or a combination of any of 1, 2-ethanedithiol, 1, 3-propanedithiol, 1, 6-hexanedithiol, 1, 10-decanedithiol, bis (3-mercaptopropionic acid) ethylene glycol, trimethylolpropane tris (3-mercaptopropionate) or tetra (3-mercaptopropyl pentaerythritol ester) ; The specific preparation method is: first melt the vanillin based acetal structure four alkene monomer at 90-120 DEG C, add the thiol monomer, then add 0.5-3 wt% of a photoinitiator 1173 or 2, 2-dimethoxy-2-phenylphenylacetophenone, stir uniformly, then solidify under ultraviolet lamp for 10-30 min, and then heat solidify at 70-140 DEG C for 0.5-12; The mixing ratio of the vanillin based acetal structure four alkene monomer to the thiol monomer is 1:1 according to the molar ratio of C=C double bond in the vanillin based acetal structure four alkene monomer to the -SH functional group in the thiol monomer.

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