Preparation and application of an efficient temperature-sensitive system

Abstract

The present invention discloses the preparation and application of an efficient temperature-sensitive system, which belongs to the field of surfactant applications and the field of intelligent materials. The present invention utilizes a novel quaternary ammonium salt surfactant synthesized from a straight-chain saturated fatty acid, methanol, 3-dimethylaminopropylamine, and (3-bromopropyl)trimethylammonium bromide; based on the novel quaternary ammonium salt surfactant, an efficient temperature-sensitive system is obtained. The temperature-sensitive system obtained by the present invention responds to temperature very quickly and can still maintain extremely high viscoelasticity at higher temperatures. After adding a certain amount of additives such as inorganic salts / organic salts to the temperature-sensitive system of the present invention, the composite system still maintains a relatively high temperature response capability, and has important application value in the fields of making children's toys, sensing elements, targeted drug release, thermal recognition systems, etc.

Description

Technical Field

[0001] The present invention relates to the preparation and application of an efficient temperature-sensitive system, and belongs to the field of surfactant application and intelligent materials. Background Art

[0002] Hydrogels have a three-dimensional network structure, generally obtained by cross-linking water through the aggregated structure of polymers or small molecules. Some hydrogels contain stimulus-responsive groups. Under certain conditions, they can respond to specific stimuli and cause significant changes in the physical and chemical properties of the system. This type of hydrogel is called a stimulus-responsive hydrogel. Stimuli-responsive hydrogels not only have the advantages of excellent mechanical properties and good tissue affinity of hydrogels, but can also respond to changes in external conditions, bringing great convenience to people's use. In recent decades, hydrogels have been increasingly widely used in fields such as cell engineering, in vivo drug transport, sensing devices, oil extraction, food processing, and intelligent controlled release.

[0003] Common stimuli-responsive hydrogels can respond to changes in light, temperature, pH, and magnetic fields. In practice, these stimuli require specialized equipment. During pH response, both the structure of the groups within the system and the pH of the system change, which can lead to adverse consequences in certain biological systems. In contrast, temperature response requires no dedicated device, making the process more convenient. Furthermore, temperature changes have little effect on the molecular structure of the cross-linked hydrogel. While currently developed temperature-responsive hydrogels made from cross-linked polymers exhibit excellent mechanical properties, their large molecular structure results in minimal viscosity changes before and after temperature fluctuations, resulting in a low efficiency in temperature response. Therefore, developing a hydrogel system with a significant viscosity change before and after temperature fluctuations would be a pressing challenge and would facilitate the development of thermosensitive hydrogels. Furthermore, the viscosity of most hydrogel systems decreases with increasing temperature. Developing a system whose viscosity increases with temperature would have significant application prospects in fields such as energy conversion and fluorescence detection. Summary of the Invention

[0004] Technical issues

[0005] Currently developed systems that respond to UV / visible light and pH values ​​not only require specific generating devices or additives during the regulation process, but may also cause trouble in certain practical applications. In contrast, temperature regulation is more convenient and has a high response efficiency. Currently reported are mainly temperature-responsive polymer hydrogels. Due to the large molecular structure, the viscosity of this type of system does not change much before and after temperature changes, and the response efficiency is low. The present invention intends to use small molecule surfactants with a new structure and utilize a unique molecular assembly mechanism to solve the above problems.

[0006] Technical Solution

[0007] The present invention provides a temperature-sensitive system with high response efficiency, and the preparation method thereof comprises:

[0008] The quaternary ammonium surfactant represented by formula (1) is dissolved in water, an additive is added, and the mixture is mixed to obtain a temperature-sensitive system; the temperature-sensitive system means that when the system temperature is not lower than the transition temperature, a hydrogel structure is formed; when the system temperature is lower than the transition temperature, a fluid solution is formed;

[0009]

[0010] Where n is 10-24, m is 1-6, i is 1-6, X- is a halogen ion (F, Cl, Br, I), NO3 - 、SO3 - ;

[0011] The additive is an inorganic salt and / or a small molecule carboxylate without alkane; the concentration of the additive relative to water is 0-100g·L -1 .

[0012] In one embodiment of the present invention, the transition temperature is 30-60°C.

[0013] In one embodiment of the present invention, the concentration of the quaternary ammonium surfactant relative to water is 10 mmol·L -1 -1500mmol·L -1 Specific can be 600-800mmol·L -1 ; 700-800mmol·L -1 .

[0014] In one embodiment of the present invention, when the concentration of the additive relative to water is 0, the system transforms from a mobile solution to a hydrogel at a temperature above 30°C.

[0015] Specifically, when the concentration of quaternary ammonium surfactant relative to water is 800mmol·L -1 When the temperature is above 30℃, the system changes from a mobile solution to a hydrogel; when the concentration of the quaternary ammonium surfactant relative to water is 700mmol·L -1 When the temperature is above 40℃, the system changes from a mobile solution to a hydrogel.

[0016] In one embodiment of the present invention, when the concentration of the additive relative to water is not 0, the system transforms from a mobile solution to a hydrogel at a temperature above 30°C.

[0017] Specifically, when the concentration of quaternary ammonium surfactant relative to water is 800mmol·L -1When the temperature is above 30℃, the system changes from a mobile solution to a hydrogel; when the concentration of the quaternary ammonium surfactant relative to water is 700mmol·L -1 When the temperature is above 35℃, the system changes from a mobile solution to a hydrogel; when the concentration of the quaternary ammonium surfactant relative to water is 600mmol·L -1 When the temperature is above 55℃, the system changes from a mobile solution to a hydrogel.

[0018] In one embodiment of the present invention, the concentration of the additive relative to water is further 0.05-0.5 g·L -1 ; Specific optional 0.05g·L -1 , 0.25g·L -1 , or 0.5 g·L -1 .

[0019] In one embodiment of the present invention, the inorganic salt comprises NaCl and / or CaCl2.

[0020] In one embodiment of the present invention, the alkane-free small molecule carboxylate can specifically be sodium salicylate NaSal.

[0021] In one embodiment of the present invention, the quaternary ammonium surfactant is synthesized using a linear saturated fatty acid shown in Formula 2, methanol, a 3-dimethylaminoalkylamine shown in Formula 3, and a (3-bromoalkyl)trimethylammonium bromide shown in Formula 4;

[0022]

[0023] In one embodiment of the present invention, the synthesis route of the quaternary ammonium salt surfactant is as follows:

[0024]

[0025] In one embodiment of the present invention, a quaternary ammonium surfactant is synthesized from a linear saturated fatty acid, methanol, 3-dimethylaminopropylamine, and (3-bromopropyl)trimethylammonium bromide as shown in Formula 2, and is denoted as C n+3 -3-2N.

[0026] In one embodiment of the present invention, the viscosity of the system increases with increasing temperature, and the higher viscosity can increase to more than 1 million times that of the initial system.

[0027] The present invention also provides application of the temperature-sensitive system in the preparation of a sensing device.

[0028] The present invention also provides application of the temperature-sensitive system in the construction of a thermal recognition system.

[0029] The present invention also provides application of the temperature-sensitive system in oil production.

[0030] The present invention also provides the application of the temperature-sensitive system in the preparation of food processing equipment and children's toys.

[0031] The present invention also provides application of the temperature-sensitive system in the preparation of an intelligent controlled-release system.

[0032] Beneficial effects:

[0033] The novel temperature-sensitive composite system provided by the present invention responds to temperature extremely quickly and can cause a significant change in the viscosity of the system when the temperature change range reaches 3°C. After heating, the maximum viscosity of the system can change by up to 1 million times compared with the viscosity of the solution at low temperature. The composite system can be transformed into a hydrogel at a temperature as low as 30°C and still has excellent viscoelasticity at a temperature of 85°C, and also has good tolerance to inorganic and organic salts. This sensitive and efficient temperature response performance can be applied to the production of children's toys, sensing elements, targeted drug release, thermal recognition systems and other fields, and the performance of the solution viscosity increasing with increasing temperature gives it significant application potential in the process of oil reservoir exploitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 C 18 -3-2N H NMR spectrum (DMSO).

[0035] Figure 2 800mmol·L at different temperatures -1 C 18 Steady-state shear rheology diagram of the -3-2N system.

[0036] Figure 3 800mmol·L -1 C 18 -3-2N system zero shear viscosity versus temperature.

[0037] Figure 4 700mmol·L -1 C 18 -3-2N system in different (a) C NaSal (b) C NaCl (c) C CaCl2 Steady-state rheological diagram under (solid symbols represent 25°C, open symbols represent 65°C).

[0038] Figure 5 800mmol·L -1 C 18 -Appearance of the 3-2N system (the left picture was taken at 25°C, and the right picture was taken after heating to 40°C).

[0039] Figure 6 800mmol·L-1 C 18 -Appearance of the 3-2N system (the left picture was taken at 40°C, and the right picture was taken after cooling to 25°C).

[0040] Figure 7 700mmol·L -1 C 18 -3-2N system at 0.25g·L -1 Appearance pictures of NaSal (a, d), NaCl (b, e), and CaCl2 (c, f) under different salt concentrations (the left picture was taken at 25°C, and the right picture was taken after heating to 50°C).

[0041] Figure 8 700mmol·L -1 C 18 -3-2N system at 0.25g·L -1 Appearance pictures at different NaSal concentrations (the left picture was taken at 50°C, and the right picture was taken after cooling to 25°C). DETAILED DESCRIPTION

[0042] Example 1: Preparation of quaternary ammonium salt surfactant

[0043] The synthetic route is as follows:

[0044]

[0045] 250.0g of octadecanoic acid (0.88mol) and 168.7g of methanol (5.27mol) were poured into a 2000mL three-necked flask, 3mL of concentrated sulfuric acid was added as a catalyst, and the mixture was refluxed in a 70°C oil bath for 5-6h. After the reaction, 100mL of dichloromethane was added, and the mixture was washed with 50mL of deionized water and separated. 100g of anhydrous magnesium sulfate was added to the oil phase, and the mixture was allowed to dry for 30min before being filtered. The obtained organic phase was then freed of dichloromethane and other residual solvents under reduced pressure. The remaining liquid was purified by vacuum distillation to obtain Intermediate A.

[0046] 189.3 g of Intermediate A (0.63 mol) and 194.3 g of 3-dimethylaminopropylamine (1.90 mol) were added to a 1000 mL three-necked flask, along with 1 g of KOH as a catalyst. The mixture was reacted at 100°C for 48 hours. After the reaction, the mixture was placed in a 1000 mL beaker and recrystallized three times from acetone and ethanol to obtain Intermediate B.

[0047] 20.2g of intermediate B (0.05mol) and 13.3g of (3-bromopropyl)trimethylammonium bromide (0.05mol) were placed in a 500mL single-necked bottle, 80mL of ethanol was added, and the mixture was reacted at 85°C for 48h. After the reaction, the ethanol was removed under reduced pressure, and the residue was crystallized three times with a mixture of acetone and ethanol. After drying in a vacuum drying oven, the final product, a quaternary ammonium salt surfactant, was obtained, referred to as C. 18 -3-2N.

[0048] C 18 -3-2N structure and purity determination:

[0049] Take appropriate amount of C 18 -3-2N was placed in an NMR tube, dissolved in deuterated DMSO, and analyzed using a Bruker Advance III NMR spectrometer at 25°C. 1 H NMR test, 1 The resonant frequency of H is 400MHz. 18 The hydrogen nuclear magnetic resonance spectrum of -3-2N is as follows Figure 1 As shown. Figure 1 It can be seen that the chemical shift of each hydrogen is consistent with the target product C 18 -3-2N is consistent, indicating that the target product has been obtained; and there are no impurity peaks in the spectrum, indicating that the product has reached a high purity.

[0050] Example 2: Single Component C 18 -3-2N preparation of temperature-sensitive system

[0051] Prepare 3mL 800mmol·L -1 C 18 -3-2N aqueous solution is a temperature-sensitive system.

[0052] Heat up and observe the changes in the state of the thermosensitive system. The appearance of the thermosensitive system is shown in the figure below. Figure 5 As shown in the figure, the fluidity of the solution gradually decreases during the heating process. When the temperature rises to 30°C, the solution can overcome its own gravity in an inverted glass bottle without flowing, forming a hydrogel with excellent performance. When the aqueous solution is left at room temperature for a period of time and the solution temperature drops to 25°C, the solution returns to a fluid state, as shown in the figure below. Figure 6 As shown, its transition temperature is 30℃.

[0053] In addition, 3 mL 700 mmol·L -1 、600mmol·L -1 C 18 -3-2N aqueous solution in a sample bottle with a cap to obtain the corresponding temperature-sensitive system. The results showed that: 700mmol·L -1The transition temperature of the thermosensitive system is 40℃; 600mmol·L -1 C 18 The -3-2N thermosensitive system cannot form hydrogel when the temperature is raised to 60℃ and 65℃, and does not have obvious thermosensitivity.

[0054] Example 3: C 18 -3-2N / salt compound preparation of temperature-sensitive system

[0055] Prepare 700mmol·L -1 C 18 -3-2N aqueous solution in a sample bottle with a cap, and then NaSal, NaCl and CaCl2 were added thereto respectively to obtain the corresponding preparations containing nine different salts with different salt concentrations (0.05g·L -1 , 0.25g·L -1 , 0.5g·L -1 ) surfactant mixed solution, the total volume is 3mL; the prepared solution is placed in a constant temperature box at 25±0.1℃ and allowed to stand for 24h to allow it to dissolve naturally, thereby obtaining the corresponding temperature-sensitive system.

[0056] Heat and observe the changes in the state of the temperature-sensitive system. Figure 7 As shown. During the heating process, it is obvious that the fluidity of the solution gradually decreases. When the temperature rises to 35℃, the solution can overcome its own gravity in an inverted glass bottle without flowing, forming a hydrogel with excellent performance. -1 700mmol·L of NaSal -1 C 18 -3-2N aqueous solution is left at room temperature for a period of time. When the solution temperature drops to 25℃, the solution returns to a fluid state. Its appearance is as shown in the figure Figure 8 shown.

[0057] In addition, in the presence of 0.05g·L -1 NaSal C 18 -3-2N aqueous solution, C 18 The concentration of -3-2N is 700mmol·L -1 Increased to 800mmol·L -1 When the temperature rises to 30℃, a hydrogel is formed. When the temperature drops to 25℃, the solution returns to a fluid state. -1 NaSal C 18 -3-2N aqueous solution, C 18 The concentration of -3-2N is 700mmol·L -1 Reduced to 600mmol·L -1, it was found that even when the solution was heated to 55°C, it could still overcome its own gravity and not flow when placed in an inverted glass bottle. This shows that after adding additives, this temperature-sensitive system can still form a hydrogel when heated to a certain temperature while reducing the amount of surfactant.

[0058] Example 4: Steady-state rheological test

[0059] The C in Example 2 18 -3-2N system and C in Example 3 18 The steady-state rheological test of the 3-2N / salt composite system was carried out using a DHR-3 rotational rheometer with a concentric cylinder fixture and a shear rate of 0.1 rad·s -1 to 600.0 rad·s -1 . Carry out C 18 During the rheological test of -3-2N system, a steady-state rheological test was conducted every 5℃; 18 -During the rheological test of the 3-2N / salt mixed system, only steady-state rheological tests were performed at 25°C and 65°C.

[0060] The steady-state rheological test results are as follows: Figure 2 、 Figure 3 、 Figure 4 shown.

[0061] Depend on Figure 2 and Figure 3 It can be seen that between 35℃ and 45℃, C 18 The viscosity of the -3-2N system (Example 2) changed significantly, increasing by 3,500 times. As the temperature continued to rise to 85°C, the viscosity continued to rise to 2,700,000 times the room temperature viscosity and reached a maximum value.

[0062] Depend on Figure 4 It can be seen that in the presence of certain concentrations of NaSal, NaCl and CaCl2 (Example 3), C 18 The -3-2N system still has a high efficiency in temperature response, and the viscosity change can still reach more than 6 orders of magnitude. -1 When C 18 The -3-2N / NaCl mixed system showed the largest viscosity change.

Claims

1. A method for preparing a temperature-sensitive system, characterized in that: include: The quaternary ammonium surfactant represented by formula (1) is dissolved in water, an additive is added, and the mixture is mixed to obtain a temperature-sensitive system; the temperature-sensitive system means that when the system temperature is not lower than the transition temperature, a hydrogel structure is formed; when the system temperature is lower than the transition temperature, a fluid solution is formed; Where n is 10-24, m is 1-6, i is 1-6, X - Halogen ions, NO3 - 、SO3 - ; The additive is an inorganic salt and / or a small molecule carboxylate without alkane; the concentration of the additive relative to water is 0-0.5g·L -1 .

2. The method according to claim 1, characterized in that The concentration of quaternary ammonium surfactant relative to water is 600mmol·L -1 -1500mmol·L -1 .

3. The method according to claim 1, characterized in that The transition temperature is 30-60°C.

4. The method according to claim 1, wherein The concentration of additive relative to water is 0.05-0.5g·L -1 .

5. The method according to claim 1, characterized in that The quaternary ammonium surfactant is synthesized using a straight-chain saturated fatty acid as shown in Formula 2, methanol, 3-dimethylaminoalkylamine as shown in Formula 3, and (3-bromoalkyl)trimethylammonium bromide as shown in Formula 4; 6. The temperature-sensitive system prepared by the method according to any one of claims 1 to 5.

7. Use of the temperature-sensitive system according to claim 6 in oil production.

8. Use of the temperature-sensitive system according to claim 6 in the preparation of a sensing device.

9. Use of the temperature-sensitive system according to claim 6 in the construction of a thermal recognition system.

10. Use of the temperature-sensitive system according to claim 6 in the preparation of children's toys.

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