A method for preparing nanoscale urushiol-based microspheres

Abstract

This invention discloses a method for preparing nanoscale urushiol-based microspheres. The method uses urushiol as the main monomer, an organic amine as the second monomer, and anhydrous ethanol as a good solvent. A Schiff base reaction is performed to generate a urushiol-amine binary copolymer. Subsequently, a poor solvent is added to induce copolymer nucleation. A weakly alkaline environment is maintained in the reaction system by adding an alkali regulator, thereby achieving continuous growth of microspheres through continuous copolymerization of urushiol and amine, as well as self-polymerization among urushiol molecules. The microspheres are then obtained by filtration, washing, and drying. This invention achieves the preparation of nanoscale urushiol-based microspheres under ambient temperature and pressure conditions through simple solution copolymerization. The resulting urushiol-based microspheres not only possess a regular spherical morphology but also a unique functional group structure, providing a novel microsphere substrate for the development and application of environmentally friendly functional microsphere products.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer materials and relates to a method for preparing natural polymer copolymer microspheres, specifically a method for preparing nanoscale urushiol-based microspheres. Background Technology

[0002] Microspheres are particulate materials with a near-spherical morphology and particle sizes ranging from nanometers to micrometers. Benefiting from their high specific surface area, tunable surface functions, and unique carrier properties, microspheres have shown broad application prospects in fields such as controlled drug release and targeted delivery, water pollution control and environmental remediation, reaction catalysts, and functional coating preparation. Currently, common microsphere material types mainly include polymer microspheres, inorganic microspheres, and organic-inorganic composite microspheres. Among these, polymer microspheres have been the most extensively researched and developed, and have the widest range of applications. These mainly include natural polymer microspheres (such as chitosan, sodium alginate, and gelatin) and synthetic polymer microspheres (such as polystyrene and polymethyl methacrylate). Correspondingly, various methods have been developed for the preparation of polymer microspheres, such as emulsion polymerization, suspension or micro-suspension polymerization, spray drying, and microfluidic spheroidization. Spray drying and microfluidic technology provide low-cost solutions for the large-scale preparation of millimeter- to micrometer-sized microspheres, while micro-suspension polymerization and emulsion polymerization technologies have enabled the leap from micrometer-sized to submicrometer-sized and even nanometer-sized microspheres.

[0003] Although synthetic polymer microspheres, represented by polystyrene and polymethyl methacrylate microspheres, have advantages such as simple preparation methods, low cost, and structural stability, they suffer from drawbacks in practical applications, including poor biocompatibility, non-degradability, and low content of surface-active groups. These inherent structural defects usually require complex surface modification to overcome. In recent years, with the deepening of green chemistry concepts and sustainable development strategies, natural polymer microspheres, which are environmentally friendly and have good biocompatibility, have gradually become ideal microsphere substrates. They possess characteristics such as renewable raw material sources and degradable polymerization products, aligning with the trends of green chemistry and sustainable development. More importantly, natural polymer materials themselves possess active groups such as amine, carboxyl, and hydroxyl groups. Microspheres prepared using these as substrates contain abundant surface functional groups, and diverse functional properties can be endowed with them through relatively simple surface modification. This provides an innovative solution for realizing microsphere surface functionalization.

[0004] Among many natural raw materials, natural polyphenols, represented by urushiol, possess unique broad-spectrum antibacterial properties, chemical reducing properties, ionic complexing properties, and universal adhesive properties due to their rich catechol (catechol) groups. Polyurushiol, a natural polymer synthesized from urushiol monomers, has shown great application potential in antibacterial, adsorption, catalysis, and sensing applications. Although studies have shown that polymerized urushiol and its derivatives have unique advantages over common natural polymers such as chitosan and cellulose in terms of group reactivity and functional diversity, urushiol monomers are viscous liquids when unpolymerized, making it impossible to directly produce solid microspheres through spray drying or microfluidic technology. At the same time, the abundant catechol groups bring extremely strong mutual adhesion and free radical scavenging ability, making it difficult to obtain nanoscale polyurushiol microspheres with controllable morphology using traditional emulsion polymerization or suspension polymerization techniques. Summary of the Invention

[0005] To address the challenge of mass production of nanoscale urushiol-based microspheres with regular morphology and controllable particle size, this invention proposes a simple and mild synthesis method for nanoscale urushiol-based microspheres. This method addresses the high adhesion and low free radical reactivity of catechol groups by employing intermolecular solution copolymerization to achieve the nucleation and growth of urushiol-based microspheres, while simultaneously introducing unsuitable solvents to control the morphology and particle size of the microspheres.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A nanoscale urushiol-based microsphere is prepared by the following steps: 1) Add urushiol and organic amine to anhydrous ethanol and stir to mix well to obtain a reaction premix; 2) Under stirring conditions, the reaction premix is ​​heated to react, causing urushiol and organic amine to undergo Schiff base reaction to form a copolymer; after 2 hours of reaction, a poor solvent is slowly added to promote the precipitation and nucleation of the urushiol-amine copolymer due to reduced solubility, and to transform the homogeneous reaction system into a heterogeneous system; then, an alkali regulator is continuously and slowly added dropwise to maintain a weakly alkaline reaction environment, and the reaction continues for 1-4 hours to ensure that the unreacted urushiol monomer can be deposited, coated and polymerized on the surface of the formed sphere core through copolymerization with amine and its own self-polymerization reaction, thereby completing the microsphere growth process; 3) After the reaction is complete, stir and mature the mixture to make the functional groups react more completely. At the same time, further reduce the solubility of urushiol microspheres in the mixed solvent, promote the full formation of microspheres and prevent them from sticking together. Then, filter, wash and dry to obtain the nano-sized urushiol-based microspheres.

[0007] Furthermore, the urushiol mentioned in step 1) is obtained by extracting it from raw lacquer using organic solvents such as ethanol and acetone.

[0008] Further, the organic amine mentioned in step 1) is one or more organic compounds or polymers that are soluble in ethanol and contain not less than two amine groups, such as diethylenetriamine, triethylenetetramine, polyethyleneimine, etc.

[0009] Furthermore, the mass ratio of urushiol to organic amine used in step 1) is 3:1 to 12:1.

[0010] Furthermore, the mass-to-volume ratio of urushiol and anhydrous ethanol used in step 1) is 30 g: 1 L.

[0011] Furthermore, the reaction temperature in step 2) is 25°C, and the stirring speed is 150 r / min.

[0012] Furthermore, the undesirable solvent mentioned in step 2) is a non-polar alkane such as n-pentane, n-hexane, n-heptane, or cyclohexane, and its addition amount is 50%-100% of the volume of anhydrous ethanol used.

[0013] Furthermore, the alkali regulator mentioned in step 2) is an alkoxide such as sodium methoxide or sodium ethoxide, and the amount added is such that the pH value of the reaction system is maintained at 8.5.

[0014] Furthermore, in step 3), the stirring and maturation temperature is 40-60℃, the time is 10-15 min, and the stirring speed is 150 r / min.

[0015] Furthermore, in step 3), a filter membrane with a pore size of 0.22 μm is used for vacuum filtration.

[0016] This invention first prepares a polymerization reaction solution using urushiol as the main monomer, an organic amine compound as the second monomer, and anhydrous ethanol as a good solvent. After the reaction begins, the catechol groups of urushiol are oxidized to a quinone structure, which then undergoes a Schiff base reaction with the amine groups under continuous stirring to generate a urushiol-amine binary copolymer. Subsequently, nonpolar alkanes, acting as poor solvents, are gradually added to the reaction system to reduce the copolymer's solubility and promote its precipitation and nucleation, transforming the homogeneous solution copolymerization system into a heterogeneous system. During this process, as the reaction proceeds, the organic amine in the system is gradually consumed, and the pH of the solution gradually decreases from weakly alkaline to neutral. At this point, an alkali adjuster needs to be added to maintain the weakly alkaline state of the reaction solution to ensure that unreacted urushiol can precipitate through copolymerization with the amine and its own self-polymerization, thereby achieving the continuous growth of microspheres. Finally, after the reaction is complete, urushiol-based microspheres with regular morphology are obtained through filtration, washing, and drying.

[0017] The beneficial effects of this invention are as follows: (1) The urushiol-based microspheres prepared from natural renewable raw materials have unique catechol groups and unsaturated long carbon side chain structures, which overcome the shortcomings of synthetic polymer microspheres such as non-degradability and low content of active groups. At the same time, it further enriches the types of groups, molecular structures and physicochemical properties of existing natural polymer microspheres, providing an ideal new microsphere substrate for the development and application of environmentally friendly functional microsphere products.

[0018] (2) The phase transition solution copolymerization process proposed in this invention can obtain nanoscale urushiol-based microspheres with uniform morphology, controllable particle size and rich active groups at low cost and on a large scale under normal temperature and pressure conditions without subsequent surface modification. It simplifies the preparation process of nanoscale functional polymer microspheres and solves the problem that traditional microsphere preparation methods cannot adapt to the characteristics of urushiol monomers and are difficult to prepare nanoscale urushiol-based microspheres with regular morphology in batches. Attached Figure Description

[0019] Figure 1 The process flow diagram and macroscopic photographs for preparing urushiol-based microspheres in Example 1 are shown.

[0020] Figure 2 The infrared spectrum of the urushiol-based microspheres prepared in Example 1 is shown.

[0021] Figure 3 The image shows the microstructure of the urushiol-based microspheres prepared in Example 1.

[0022] Figure 4 The image shows the microstructure of the urushiol-based microspheres prepared in Example 2.

[0023] Figure 5 The image shows the microstructure of the urushiol-based microspheres prepared in Example 3.

[0024] Figure 6 The image shows the microstructure of the pure urushiol polymer product prepared in Comparative Example 1.

[0025] Figure 7 The image shows the microstructure of the urushiol-based microspheres prepared in Comparative Example 2. Detailed Implementation

[0026] A nanoscale urushiol-based microsphere is prepared by the following steps: 1) Add urushiol and organic amine in a mass ratio of 3:1-12:1 to anhydrous ethanol (mass-volume ratio of urushiol to anhydrous ethanol is 30g:1L), stir and mix well to obtain a reaction premix; 2) Under stirring at 150 r / min, heat the reaction premix to 25°C for reaction; after 2 hours of reaction, slowly add 50%-100% of the volume of anhydrous ethanol as a poor solvent; after the poor solvent is added, slowly and continuously add an alkali adjuster to adjust the pH of the reaction system to 8.5, and continue the reaction for 1-4 hours. 3) After the reaction is complete, heat to 40-60℃ and continue stirring at 150r / min for 10-15min. Then filter using a 0.22μm pore size filter membrane, and then wash and vacuum dry to obtain nano-sized urushiol microspheres.

[0027] Wherein, the organic amine mentioned in step 1) is one or more of organic compounds or polymers that are soluble in ethanol and contain not less than two amine groups, such as diethylenetriamine, triethylenetetramine, polyethyleneimine, etc.

[0028] The undesirable solvent mentioned in step 2) is a nonpolar alkane such as n-pentane, n-hexane, n-heptane, and cyclohexane. The alkali adjuster is an alkoxide such as sodium methoxide and sodium ethoxide.

[0029] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods. Example 1

[0031] (1) Add 30g urushiol and 10g diethylenetriamine to 1L of anhydrous ethanol in sequence, stir thoroughly to dissolve the two substances and mix them thoroughly to obtain urushiol-amine polymerization reaction solution.

[0032] (2) The polymerization reaction solution was transferred to a glass reactor equipped with a stirrer, condenser, and heater. Cooling water was circulated and the stirring rate was controlled at 150 r / min. After stirring at 25°C for 2 h, 1 L of n-hexane was gradually added to the system to promote the precipitation and nucleation of the urushiol-amine copolymer in the mixed solvent due to the decrease in solubility. During this process, the reaction solution gradually changed from a clear brownish-yellow solution to a dark brown turbid solution.

[0033] (3) After the addition of n-hexane, sodium methoxide was slowly added dropwise to the reactor while maintaining a constant stirring rate to keep the pH of the reaction system at 8.5, and the reaction continued for 1 hour. During this process, the color of the reaction solution deepened further and visible suspended particles appeared, indicating that unreacted monomers continued to deposit, cover, and polymerize on the core surface to form microspheres.

[0034] (4) After the polymerization reaction is complete, the temperature is raised to 40°C and stirred for 10 min to further reduce the solubility of urushiol microspheres in the mixed solvent, promote the full formation of microspheres and prevent them from sticking together. Then, the reaction solution is filtered using a 0.22 μm hydrophobic microporous membrane. The filtered product is washed with ethanol and then vacuum dried to obtain urushiol-based microspheres.

[0035] like Figure 3 As shown, the higher proportion of amine groups in the formulation system increases the probability of copolymerization nucleation, while the shorter microsphere growth reaction time limits the degree of microsphere size growth. Therefore, a large number of microspheres are obtained, but the particle size is small, about 150-250 nm. Example 2

[0036] (1) Add 60g urushiol and 10g diethylenetriamine to 2L of anhydrous ethanol in sequence, stir thoroughly to dissolve the two substances and mix them thoroughly to obtain urushiol-amine polymerization reaction solution.

[0037] (2) The polymerization reaction solution was transferred to a glass reactor equipped with a stirrer, condenser and heating device. Cooling water was circulated and the stirring rate was controlled at 150 r / min. After stirring at 25°C for 2 h, 1.5 L of n-hexane was gradually added to the system. During this reaction, the solution gradually changed from a clear brown solution to a turbid brown-black solution.

[0038] (3) After the addition of n-hexane is complete, sodium ethoxide is slowly added dropwise to the reactor while maintaining a constant stirring rate to keep the pH of the reaction system at 8.5, and the reaction continues for 3 hours. Visible suspended particles appear in the reaction solution.

[0039] (4) After the polymerization reaction is complete, the temperature is raised to 50°C and stirred for 10 min. Then the reaction solution is filtered using a 0.22 μm hydrophobic microporous membrane. The filtered product is washed with ethanol and dried under vacuum to obtain urushiol microspheres.

[0040] like Figure 4 As shown, by adjusting the ratio of urushiol to amino groups and the microsphere growth time, a large number of microspheres with a medium particle size of approximately 300-500 nm were obtained. Example 3

[0041] (1) Add 120g urushiol and 10g diethylenetriamine to 4L anhydrous ethanol in sequence, stir thoroughly to dissolve the two substances and mix them thoroughly to obtain urushiol-amine polymerization reaction solution.

[0042] (2) The polymerization reaction solution was transferred to a glass reactor equipped with a stirrer, condenser and heating device. Cooling water was circulated and the stirring rate was controlled at 150 r / min. After stirring at 25°C for 2 h, 2 L of n-hexane was gradually added to the system. During this reaction, the solution gradually changed from a dark brown clear solution to a brownish-black turbid solution.

[0043] (3) After the addition of n-hexane is complete, sodium ethoxide is slowly added dropwise to the reactor while maintaining a constant stirring rate to keep the pH of the reaction system at 8.5, and the reaction continues for 4 hours. Visible suspended particles appear in the reaction solution.

[0044] (4) After the polymerization reaction is complete, the temperature is raised to 60°C and stirred for 15 min. Then the reaction solution is filtered using a 0.22 μm hydrophobic microporous membrane. The filtered product is washed with ethanol and dried under vacuum to obtain urushiol microspheres.

[0045] like Figure 5 As shown, by using a lower amine ratio and a longer microsphere growth time, fewer microspheres were obtained, but the particle size was larger, approximately 500-800 nm.

[0046] Compare with Example 1 (1) Add 30g of urushiol to 1L of anhydrous ethanol and stir thoroughly to dissolve to obtain a pure urushiol polymerization reaction solution.

[0047] (2) Transfer the reaction solution to a glass reactor equipped with a stirrer, condenser and heater. Circulate cooling water and control the stirring rate at 150 r / min. Stir the reaction at 25°C for 2 h, then gradually add 1 L of n-hexane to the system. The solution color darkens slightly during the reaction.

[0048] (3) After the addition of hexane is complete, sodium methoxide is slowly added dropwise to the reactor while maintaining a constant stirring rate to keep the pH of the reaction system at 8.5, and the reaction continues for 1 hour. During this process, a very small number of visible suspended particles appear in the reaction solution.

[0049] (4) After the polymerization reaction is complete, the temperature is raised to 40°C and stirred for 10 min. Then, the reaction solution is filtered using a 0.22 μm hydrophobic microporous membrane. The filtered product is washed with ethanol and then dried under vacuum to obtain pure urushiol self-polymerized product.

[0050] like Figure 6 As shown, since no organic amines were added to the system to participate in the copolymerization nucleation reaction, the number of urushiol self-polymerized products obtained was very small and their appearance was irregular.

[0051] Compare with Example 2 (1) Add 30g urushiol and 10g diethylenetriamine to 1L of anhydrous ethanol in sequence, stir thoroughly to dissolve the two substances and mix them thoroughly to obtain urushiol-amine polymerization reaction solution.

[0052] (2) The polymerization reaction solution was transferred to a glass reactor equipped with a stirrer, condenser, and heater. Cooling water was introduced and the stirring rate was controlled at 150 r / min. After stirring and reacting at 25°C for 2 h, sodium methoxide was slowly added dropwise to the reactor to control the pH of the reaction system at 8.5, and the reaction was continued for 1 h. During this process, the color of the reaction solution changed from brownish-yellow before the reaction to brownish-black and a small number of visible suspended particles appeared.

[0053] (3) After the polymerization reaction is complete, the temperature is raised to 40°C and stirred for 10 min. Then the reaction solution is filtered using a 0.22 μm hydrophobic microporous membrane. The filtered product is washed with ethanol and dried under vacuum to obtain urushiol microspheres.

[0054] like Figure 7 As shown, due to the lack of the addition of unsuitable solvents to assist in microsphere formation, the resulting microspheres have irregular morphology and exhibit significant agglomeration.

[0055] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing nanoscale urushiol-based microspheres, characterized in that, Includes the following steps: 1) Add urushiol and organic amine to anhydrous ethanol and stir to mix well to obtain a reaction premix; 2) Under stirring conditions, the reaction premix was heated to carry out the reaction. After 2 hours of reaction, the unsuitable solvent was slowly added, followed by the continuous addition of the alkali regulator, and the reaction was continued for 1-4 hours. 3) After the reaction is complete, stir and mature the mixture, then filter, wash and dry it to obtain the nano-sized urushiol microspheres.

2. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, The organic amine mentioned in step 1) is one or more organic compounds or polymers that are soluble in ethanol and contain not less than two amine groups.

3. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, The mass ratio of urushiol and organic amine used in step 1) is 3:1-12:

1.

4. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, The mass-to-volume ratio of urushiol and anhydrous ethanol used in step 1) is 30 g: 1 L.

5. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, The reaction temperature in step 2) is 25°C, and the stirring speed is 150 r / min.

6. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, The undesirable solvent mentioned in step 2) is a nonpolar alkane, and its addition amount is 50%-100% of the volume of anhydrous ethanol used.

7. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, The alkali adjuster mentioned in step 2) is an alkoxide, and the amount added is such that the pH value of the reaction system is maintained at 8.

5.

8. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, The stirring and maturation temperature in step 3) is 40-60℃, the time is 10-15 min, and the stirring speed is 150 r / min.

9. The method for preparing nanoscale urushiol-based microspheres according to claim 1, characterized in that, In step 3), a filter membrane with a pore size of 0.22 μm is used for vacuum filtration.

10. A nanoscale urushiol-based microsphere prepared by the method described in claim 1.

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