CN103920432B - A kind of lightweight, flexible super hydrophobic porous gas-gel material and preparation method thereof - Google Patents

Abstract

The present invention is a lightweight, flexible super-hydrophobic porous gas gel material, which is prepared by the following method, the first step: adding urea, carboxylic acid ionic liquid solution and surfactant to the reactor and mixing, the second Step 1: Stir and then add siloxane. Step 3: Transfer to a reaction kettle, polymerize and age in an oven at 70-90°C for 5-8 hours. Step 4: wash with double-distilled water and ethanol successively, and dry at normal temperature and pressure to obtain a lightweight, flexible superhydrophobic porous gas gel material. The material has small density, large porosity, easy to bend, spring back after compression, super hydrophobicity, can be applied in the temperature range of 77K-573K, stable pore can withstand solution modification and other excellent characteristics.

Description

A light, flexible superhydrophobic porous gas gel material and its preparation method

technical field

The technical solution of the present invention relates to the preparation of porous gas gel, specifically a light, flexible super-hydrophobic porous gas gel material and a preparation method thereof.

Background technique

Aerogel is a kind of highly dispersed porous solid material. Its porous solid structure is composed of colloidal particles or polymer molecules, and the pores are filled with gaseous dispersion medium. between nanometers. Aerogels have the advantages of low thermal conductivity, low density, high porosity, large specific surface area, and controllable structure and doping, making them widely used as adsorbents, gas storage, catalyst supports, filters, membranes, and separation media. Typical silica aerogels, usually prepared by sol-gel process, have high porosity (>90%) and small pore size (~50 nm), and the porous structure consists of aggregates of silica nanoparticles (~ 10nm) composition. However, the highly fragile network structure of silica aerogels prevents them from being fabricated and processed in large sizes. In order to improve the performance of gas gels, many efforts have been made. For example, the PMSQ gel invented by the Japanese (K.Kanamori, Y.Kodera, G.Hayase, K.Nakanishi, T.Hanada, J.ColloidInterfaceSci.2011, 357, 336), the density can reach 0.22gcm ^-3 , has a flexible network shape structure, which improves the performance of the gas gel. However, some fatal shortcomings limit its practical application. For example harsh drying conditions: supercritical drying, freeze drying. Drying at normal temperature and pressure is favored by people because the method is simple, but in the drying process at normal temperature and pressure, the pores are not stable enough, causing the density to increase (AS Dorcheh, M.Abbasi, J.Mater.Process.Technol.2008, 199, 10.). In addition, the use of acetic acid as an acidic medium is likely to cause environmental pollution. How to use a solvent that can maintain the stability of the pores and be environmentally friendly under normal temperature and pressure drying conditions is still blank.

Ionic liquids have attracted widespread attention in recent years because of their low vapor pressure, good electrical conductivity, and their potential as solvents in liquid-liquid extraction. Furthermore, different combinations of cations and anions lead to different properties of ionic liquids. Carboxylic acid ionic liquids not only have the high-density reactive sites of liquid acids, but also have the non-volatility of solid acids, and have the characteristics of low melting point, non-flammability, high thermal stability, liquid state at room temperature, and low toxicity. The series of advantages of ionic liquids make it an environmentally friendly catalyst and efficient green solvent, and it has already become a feature of chemical frontiers and research in today's chemistry. In recent years, people's research and application of it have become more and more extensive, and the designability of the structure of ionic liquid makes its acidity adjustable, and its mild acidity makes its application prospect more optimistic.

Contents of the invention

The technical problem to be solved by the present invention is: based on the excellent characteristics of ionic liquids, the acetic acid solution used in other materials is replaced by the green solvent carboxylic acid ionic liquid as the acidic medium, and a super-hydrophobic porous gas is synthesized by simple four-step operation gel. This method is simple, economical and environmentally friendly. The prepared material has such excellent characteristics as small density, large porosity, easy to bend, spring back after compression, super hydrophobicity, can be applied in the temperature range of 77K-573K, and the channel is stable and can withstand solution modification.

The technical solution adopted by the present invention to solve the technical problem is:

A light, flexible superhydrophobic porous gas gel material, which is prepared by the following method, comprising the following steps:

The first step: Add urea, carboxylic acid ionic liquid solution and surfactant to the reactor and mix them. The molar ratio is urea: water: carboxylic acid ionic liquid: surfactant = (37.9 ~ 45.5): 353.5: (2.5 ×10 ^-3 ～50×10 ^-3 ): 1;

The second step: add siloxane under stirring, wherein siloxane is a mixture of trimethoxysilane and dimethoxysilane, the molar ratio of the two is trimethoxysilane:dimethoxysilane (DMDMS) = 3:2, stirring until the hydrolysis of siloxane is complete; wherein the molar ratio of dimethoxysilane to surfactant in the first step is 6.37:1;

The third step: transfer to the reaction kettle, polymerize and age in an oven at 70-90°C for 5-8 hours;

Step 4: wash with double-distilled water and ethanol successively, and dry at normal temperature and pressure to obtain a lightweight, flexible superhydrophobic porous gas gel material.

The carboxylic acid ionic liquid is imidazole carboxylic acid ionic liquid, pyridine carboxylic acid ionic liquid or betaine hydrochloride.

The structural formula of the imidazole carboxylic acid ionic liquid (I) is as follows:

Wherein, R is a straight-chain alkane group.

Preferably CH ₃ , C ₄ H ₇ , C ₈ H ₁₅ , C ₁₂ H ₂₃ or C ₁₆ H ₃₁

The structural formula of pyridinecarboxylic acid ionic liquid (II) is as follows:

Said A=Br, CF ₃ COO, HSO ₄ , H ₂ PO ₄ or BF ₄ .

The surfactant is cetyltrimethylammonium bromide (CTAB).

The trimethoxysilane is one or two of methyltrimethoxysilane (MTMS), vinyltrimethoxysilane (VTMS) and trithiopropyltrimethoxysilane (MPTMS).

Described dimethoxysilane is methyldimethoxysilane (DMDMS), and structural formula is as follows:

The beneficial effects of the present invention are:

(1) Using carboxylic acid ionic liquid as the acidic medium is environmentally friendly, and the mild acidity of carboxylic acid ionic liquid can optimize the structure of the pores, can withstand the modification of the solution, and maintain the stability of the pores. The dimension of the inventive material remains stable after being dried under normal temperature and normal pressure. In addition, after the material prepared by the present invention is immersed in water and ethanol solution for secondary drying, the original size remains unchanged, the microscopic appearance is similar, and the nitrogen adsorption curve is basically consistent.

(2) The airgel material prepared by the present invention has a density as low as 0.1 g/cm ³ or less, and can efficiently adsorb organic matter. For example, using butyl carboxylic acid ionic liquid (ILC4) as an acidic medium, and using methyltrimethoxysilane and methyldimethoxysilane as precursors, the density of the gas gel material can reach 0.075g/cm ³ . Efficient hydrophobicity, the contact angle with water can reach 155°. The adsorption capacity of n-hexane reaches 7.2 times of its own weight. Under the same circumstances, the gas gel material prepared with acetic acid solution as an acidic medium has a density of 0.12g/cm ³ and an adsorption capacity of 6.2 times its own weight (G. Hayase, K. Kanamori, * M. Fukuchi, H. Kaji , and K. Nakanishi. Angew. Chem. Int. Ed. 2013, 52, 1986–1989). The low density and good adsorption performance of the inventive material make it more widely used in the field of separation and analytical chemistry.

(3) The material of the present invention has a high degree of softness, is very easy to bend and does not deform after repeated bending. For example, the flexural modulus of the gas gel material prepared by using methyl carboxylic acid ionic liquid as the acidic medium and methyltrimethoxysilane and methyldimethoxysilane as the precursor is as low as 0.02MPa, which shows that the flexural modulus is very small. This material is extremely easy to bend and very flexible.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention will be further described

Figure 1: Photo of the gas gel material produced in Example 1 under a fluorescent lamp.

Figure 2: Scanning electron microscope pictures of the gas gel material produced in Example 1. 2a is the scanning electron microscope picture of the gas gel material with a magnification of 6000, and 2b is the scanning electron microscope picture of the gas gel material with a magnification of 12000.

Figure 3: digital photographs of the size comparison of the product airgel material of Example 2 before and after secondary drying under the fluorescent lamp.

Figure 4: Scanning electron microscope pictures of the gas gel material produced in Example 2. 4a is the scanning electron micrograph of the preliminarily prepared airgel material; 4b is the scanning electron micrograph of the second drying after soaking in water; 4c is the scanning electron micrograph of the second drying after soaking in ethanol.

Figure 5: Comparison of nitrogen adsorption before and after secondary drying of the material in Example 2.

Figure 6: Digital photographs of the airgel material produced in Example 5 before and after drying under fluorescent lamps.

Figure 7: 80% three-point stress test bending curve of the product gas gel material of Example 9.

Fig. 8: Test graphs of the contact angle of the product gas gel material of Example 1 and the adsorption capacity of n-hexane. 8a is the test diagram of the contact angle between the gas gel material and water, and 8b is the adsorption diagram of 20 cycles of n-hexane.

detailed description:

In order to illustrate the present invention more clearly, the following examples are cited, but they do not limit the scope of the invention in any way.

The imidazole carboxylic acid ionic liquid involved in the present invention is synthesized according to the literature (HRLi, *D.Li, YGWang, and Q.R.Ru; Chem.AsianJ.2011,6,1443-1449), such as the methyl carboxylate used in the following examples Acid ionic liquid (I, R=CH ₃ ), butyl carboxylate ionic liquid (I, R=C ₄ H ₇ ) and hexadecyl carboxylate ionic liquid (I, R=C ₁₆ H ₃₁ );

The pyridinecarboxylic acid ionic liquid involved is synthesized according to the literature (Li Xincong, Wu Manjiang. Ai Li. Chemical Reagent, 2008, 30(5), 328-330; 334), such as the sulfopyridinecarboxylic acid ionic liquid used (Ⅱ, A=HSO ₄ )

Betaine HCl (99%) was purchased from Aladdin. However, the desired carboxylic acid ionic liquid of the present invention is not limited thereto.

Example 1

Step 1: Take 3.0g (0.05mol) of urea and 0.4g of cetyltrimethylammonium bromide (0.0011mol), add it to 7ml of 4mM butyl carboxylate ionic liquid (Ⅰ, where R=C ₄ H ₇ , denoted as ILC ₄ ), mix well.

Step 2: Add 0.0105 mol methyltrimethoxysilane (MTMS) and 0.007 mol methyldimethoxysilane (DMDMS) to the mixed solution in the first step while stirring mechanically, and stir continuously for 30 minutes until the hydrolysis is complete.

The third step: transfer the mixed solution in the second step to a reaction kettle, and gel and age in an oven at 80° C. for 7 hours.

Step 4: Repeatedly washing with double distilled water and ethanol by manual immersion-extrusion, and drying at normal temperature and pressure to obtain a porous gas gel material. Marked as: ILC ₄ -MTMS-DMDMS.

The digital photo of the product gas gel material of this example under the fluorescent lamp is shown in Figure 1. The size of the material obtained therein is 25mm×25mm×6mm.

The scanning electron microscope picture of the gas gel material of the product of this embodiment is shown in Figure 2, wherein a is the scanning electron microscope picture of the gas gel material with a magnification of 6000, and b is the scanning electron microscope picture of the gas gel material with a magnification of 12000. The scanning electron microscope image shows the loose pore structure of the airgel material.

The contact angle of the product gas gel material of this example and the adsorption capacity test of n-hexane are shown in Figure 8, wherein 8a is the test diagram of the contact angle between the gas gel material and water, and 8b is the adsorption diagram of 20 cycles of n-hexane. According to the test, the contact angle between the gas gel material and water is 155°C, and the average adsorption capacity of n-hexane is 7.2 times of its own weight.

Example 2

Vinyltrimethoxysilane (VTMS) was used to replace methyltrimethoxysilane (MTMS) in Example 1, and other steps were the same as Example 1. The obtained gas gel material is recorded as: ILC ₄ -VTMS-DMDMS. After drying, the obtained gas gel material is respectively immersed in water and ethanol at normal temperature and pressure for secondary drying.

Figure 3 shows the size comparison digital photos of the product gas gel material in this example before and after secondary drying under the fluorescent lamp. The size of the material remains stable before and after secondary drying, indicating that the size of the airgel material is not affected by solution modification.

The scanning electron microscope picture of the gas gel material produced in this example is shown in FIG. 4 . 4a is the scanning electron microscope picture of the preliminarily prepared air gel material; 4b is the scanning electron microscope picture of the second drying after soaking in water; 4c is the scanning electron microscope picture of the second drying after soaking in ethanol. Comparing the scanning electron microscope pictures before and after secondary drying, it can be seen that the microscopic morphology of the airgel material before and after secondary drying remains consistent.

The comparison chart of nitrogen adsorption before and after secondary drying of the material in this example is shown in Fig. 5 . Comparing the nitrogen adsorption graphs of the material before and after secondary drying, the nitrogen adsorption curves are basically consistent, which further shows that the material has stable pores and is not affected by solution modification.

Example 3

Methyltrimethoxysilane (MTMS) in Example 1 was replaced with methyltrimethoxysilane (MTMS) and trithiopropyltrimethoxysilane (MPTMS). Specific steps are as follows:

1. Take urea 3.0 (0.05mol) g, cetyltrimethylammonium bromide (CTAB) 0.4g (0.0011mol), add to 7ml butyl carboxylate ionic liquid (ILC ₄ ) with a concentration of 4mML ^-1 In, mix well.

2. While mechanically stirring the mixed solution in 1, add methyltrimethoxysilane (MTMS) and trimethoxypropyltrimethoxysilane (MPTMS, 0.00525mol) at a molar ratio of 1:1, and stir continuously for 30min until Hydrolysis is complete. Other steps are with embodiment 1. The obtained airgel material is denoted as: ILC ₄ -MTMS/MPTMS-DMDMS.

Example 4

Vinyltrimethoxysilane (VTMS, 0.00525mol) was used instead of methyltrimethoxysilane (MTMS) in Example 3, and other steps were the same as in Example 3. The obtained airgel material is denoted as: ILC4-VTMS/MPTMS-DMDMS.

Example 5

The butyl carboxylate ionic liquid (ILC ₄ ) in Example 1 was replaced with 7 ml of betaine hydrochloride with a concentration of 0.4 mM, and the other steps were the same as in Example 1. The obtained airgel material is denoted as: BETHCL-MTMS-DMDMS.

The digital photos of the product gas gel material in this example before and after drying under the fluorescent lamp are shown in FIG. 6 . Comparing the size before and after drying, it can be seen that the size of the airgel material remains stable before and after drying.

Example 6

The butyl carboxylate ionic liquid (ILC ₄ ) in Example 2 was replaced with 7 ml of betaine hydrochloride with a concentration of 0.4 mM, and the other steps were the same as in Example 2.

Example 7

The butyl carboxylate ionic liquid (ILC ₄ ) in Example 3 was replaced with 7 ml of betaine hydrochloride with a concentration of 0.4 mM, and the other steps were the same as in Example 3.

Example 8

The butyl carboxylate ionic liquid (ILC ₄ ) in Example 4 was replaced with 7 ml of betaine hydrochloride with a concentration of 0.4 mM, and the other steps were the same as in Example 4.

Example 9

The butyl carboxylate ionic liquid (ILC ₄ ) in Example 1 was replaced with 7 ml of methyl carboxylate ionic liquid (I, where R=CH ₃ , denoted as ILC ₁ ) with a concentration of 4 mM, and the other steps were the same as in Example 1.

The bending curve of the 80% three-point stress test of the product gas gel material of this example is shown in FIG. 7 . After 20 bending cycles, the stress curve remains consistent, and the flexural modulus is 0.02 MPa, indicating that the material is extremely bendable and flexible.

Example 10

The butyl carboxylate ionic liquid (ILC ₄ ) in Example 2 was replaced with 7 ml of methyl carboxylate ionic liquid (ILC ₁ ) with a concentration of 4 mM, and the other steps were the same as in Example 2.

Example 11

The butyl carboxylate ionic liquid (ILC ₄ ) in Example 3 was replaced with 7 ml of methyl carboxylate ionic liquid (ILC ₁ ) with a concentration of 4 mM, and the other steps were the same as in Example 3.

In Example 12, the butyl carboxylate ionic liquid (ILC ₄ ) in Example 4 was replaced by 7 ml of methyl carboxylate ionic liquid (ILC ₁ ) with a concentration of 4 mM, and the other steps were the same as in Example 4.

In Example 13, the butyl carboxylate ionic liquid (ILC ₄ ) in Example 1 was replaced by 7 ml of hexadecyl carboxylate ionic liquid (I, wherein R=C ₁₆ H ₃₁ , denoted as ILC ₁₆ ) with a concentration of 4 mM, Other steps are with embodiment 1.

Example 14

The butyl carboxylic acid functionalized ionic liquid (ILC4) in Example 2 was replaced with 7 ml of hexadecyl carboxylic acid ionic liquid (ILC ₁₆ ) with a concentration of 4 mM, and the other steps were the same as in Example 2.

Example 15

The butyl carboxylate ionic liquid (ILC4) in Example 3 was replaced with 7 ml of hexadecyl carboxylate ionic liquid (ILC ₁₆ ) with a concentration of 4 mM, and the other steps were the same as in Example 3.

In Example 16, 7 ml of hexadecyl carboxylic acid ionic liquid (ILC ₁₆ ) with a concentration of 4 mM was used to replace the butyl carboxylic acid ionic liquid (ILC4) in Example 4, and the other steps were the same as in Example 4.

In Example 17, 7 ml of sulfopyridinecarboxylic acid ionic liquid (II, A=HSO ₄ ) with a concentration of 1 mM was used to replace the butylcarboxylic acid ionic liquid (ILC ₄ ) in Example 1, and the other steps were the same as in Example 1.

Example 18

The butylcarboxylic acid functionalized ionic liquid (ILC4) in Example 2 was replaced with 7ml of sulfopyridinecarboxylic acid ionic liquid with a concentration of 1 mM, and the other steps were the same as in Example 2.

Example 19

The butylcarboxylate ionic liquid (ILC4) in Example 3 was replaced with 7ml of sulfopyridinecarboxylic acid ionic liquid with a concentration of 1 mM, and the other steps were the same as in Example 3.

Example 20

The butylcarboxylate ionic liquid (ILC4) in Example 4 was replaced with 7 ml of sulfopyridinecarboxylic acid ionic liquid with a concentration of 1 mM, and the other steps were the same as in Example 4.

Lightweight, flexible superhydrophobic porous gas gel materials can be prepared by changing siloxane and carboxylic acid ionic liquids in the above embodiments, and the material has small density, large porosity, easy bending, and can be compressed after compression. Rebound, can be applied in the temperature range of 77K-573K, can withstand solution modification and other excellent characteristics. The inventive material has a strong adsorption capacity for organic matter and is widely used in analytical chemistry and O/W separation.

Table 1: The pore properties of each substance (the density is obtained by the mass and volume of the overall framework. The porosity is obtained by the formula: porosity ε=(1-V _b /V _s )×100%, where V _b represents the solid density, and V _s represents Overall framework density. Specific surface area, pore diameter, and pore volume are measured by instrument ASAP2020V3.04H).

Matters not described in the present invention are known technologies.

Claims (4)

1. A lightweight, flexible superhydrophobic porous gas gel material, characterized in that the material is made by the following method, comprising the following steps: The first step: Add urea, carboxylic acid ionic liquid solution and surfactant to the reactor and mix them. The molar ratio is urea: water: carboxylic acid ionic liquid: surfactant = (37.9 ~ 45.5): 353.5: (2.5 ×10 ^-3 ～50×10 ^-3 ): 1; The second step: add siloxane under stirring, wherein siloxane is a mixture of trimethoxysilane and dimethoxysilane, the molar ratio of the two is trimethoxysilane:dimethoxysilane (DMDMS) = 3:2, stirring until the hydrolysis of siloxane is complete; wherein the molar ratio of dimethoxysilane to surfactant in the first step is 6.37:1; The third step: transfer to the reaction kettle, polymerize and age in an oven at 70-90°C for 5-8 hours; Step 4: Wash with double-distilled water and ethanol successively, and dry at normal temperature and pressure to obtain a lightweight, flexible super-hydrophobic porous gas gel material; Described carboxylic acid ionic liquid is imidazole carboxylic acid ionic liquid, pyridine carboxylic acid ionic liquid or betaine hydrochloride; The surfactant is cetyltrimethylammonium bromide (CTAB); The trimethoxysilane is one or both of methyltrimethoxysilane (MTMS), vinyltrimethoxysilane (VTMS) and trithiopropyltrimethoxysilane (MPTMS); The dimethoxysilane is methyldimethoxysilane (DMDMS). 2. The lightweight, flexible superhydrophobic porous gas gel material as claimed in claim 1, characterized in that the structural formula of the imidazole carboxylic acid ionic liquid (I) is as follows: (I) Wherein, R is a straight-chain alkane group. 3. The lightweight, flexible superhydrophobic porous gas gel material according to claim 2, characterized in that R is preferably CH ₃ , C ₄ H ₇ , C ₈ H ₁₅ , C ₁₂ H ₂₃ or C ₁₆ H ₃₁ . 4. The lightweight, flexible superhydrophobic porous gas gel material as claimed in claim 1, characterized in that the structural formula of the pyridine carboxylic acid ionic liquid (II) is as follows: (Ⅱ) Wherein, A=Br, CF ₃ COO, HSO ₄ , H ₂ PO ₄ or BF ₄ .