Composite polydopamine aromatic microcapsule and preparation method thereof

Abstract

The invention discloses a composite polydopamine aromatic microcapsule and a preparation method thereof, the core material of the composite polydopamine aromatic microcapsule is aromatic oil, a Pickering emulsion is prepared by encapsulating an aromatic compound through cellulose nanocrystals (CNC), and then a polyphenol compound is deposited outside emulsion drops to form an elastic interface film, so that the composite polydopamine aromatic microcapsule is prepared. And the outermost layer is coated with polydopamine. The composite polydopamine aromatic microcapsule disclosed by the invention can realize mechanical stimuli-responsive release, and the utilization rate of aromatic oil can be remarkably improved; the preparation method is simple, the reaction conditions are mild, the used raw materials are biodegradable substances, the green and environment-friendly requirements are met, and the application prospect is good.

Description

Technical Field

[0001] The invention relates to the technical field of daily chemicals, and relates to a composite polydopamine aromatic microcapsule and a preparation method thereof, and in particular to a composite polydopamine aromatic microcapsule with simple and feasible preparation process, good adhesion performance, good mechanical properties and adjustable properties, and a preparation method thereof. Background Art

[0002] Spices and flavors are widely used in many industries due to their unique aromatic properties and multiple functions, such as refreshing, antibacterial and antiseptic. However, due to their strong volatility and poor stability, especially prone to oxidation reactions under high temperature and light conditions, their application effect is limited. To solve this problem, microencapsulation technology was introduced to encapsulate spices and flavors. Through microencapsulation, not only can the stability of spices and flavors be significantly improved and protected from the influence of the external environment, but also precise control of release can be achieved, thereby improving their use efficiency and economic value.

[0003] The application of aromatic microcapsules in textiles is becoming more and more extensive, but their effectiveness is limited by their insufficient adhesion on the fabric surface. The excellent adhesion properties of polydopamine provide a good solution for the preparation of highly adhesive aromatic microcapsules. For example, CN 202310964066.1 proposes a method for preparing polydopamine microcapsules using a composite template. Although it can achieve effective encapsulation and controlled release of the target substance, its process is complicated and has many limitations. It requires multi-step operation, including the selection and pretreatment of the template, the control of the polymerization reaction, and the final removal of the template, which may also affect the quality and performance of the microcapsules.

[0004] Compared with the traditional complex template method for preparing microcapsules, the method of in situ deposition of polydopamine by emulsion can achieve one-step molding of microcapsules, which greatly simplifies the preparation process and reduces production costs. However, the polydopamine microcapsules prepared by this method often have weak mechanical properties.

[0005] Therefore, a polydopamine microcapsule with simple preparation process and good mechanical properties is of great practical significance. Summary of the invention

[0006] Due to the above-mentioned defects in the prior art, the present invention provides a polydopamine microcapsule with a simple preparation process and good mechanical properties, specifically a composite polydopamine aromatic microcapsule with a simple and feasible preparation process, good adhesion performance, good mechanical properties and adjustable properties and a preparation method thereof, which can be applied to the fields of daily chemicals, textiles, agriculture, etc., and overcomes the defect that it is difficult for polydopamine microcapsules to achieve both a simple preparation process and excellent mechanical properties.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A composite polydopamine aromatic microcapsule, the core material of the composite polydopamine aromatic microcapsule is aromatic oil, which is prepared by encapsulating aromatic compounds with CNC (cellulose nanocrystals) to obtain a Pickering emulsion, then depositing polyphenol compounds outside the emulsion droplets to form a film, and coating polydopamine on the outermost layer.

[0009] Pickering emulsion is obtained by self-assembly of CNC (cellulose nanocrystals) and amino-functionalized polymer ligands at the oil-water interface. Polyphenol compounds are adsorbed on the surface of the emulsion droplets in turn to form an elastic interfacial film. The polydopamine layer is formed by in situ deposition of dopamine (dopamine monomer undergoes oxidative self-polymerization in the outermost layer of the emulsion droplets to produce polydopamine), thus obtaining microcapsules with high adhesion and excellent mechanical properties.

[0010] The composite polydopamine aromatic microcapsules of the present invention are made of bio-based materials such as CNC (cellulose nanocrystals), polyphenols and dopamine, which not only enhance the biocompatibility and biodegradability of the microcapsules, but also improve the preparation method by compounding tannic acid and dopamine, further improving the stability, adhesion and mechanical strength of the microcapsules and broadening their application scenarios.

[0011] As the preferred technical solution:

[0012] A composite polydopamine aromatic microcapsule as described above, wherein the aromatic oil is selected from one or more of limonene, linalool and cinnamaldehyde;

[0013] The polyphenolic compound is selected from one or more of tannic acid, anthocyanin, resveratrol and quercetin.

[0014] In addition, the present invention also provides a method for preparing the composite polydopamine aromatic microcapsules as described above, comprising the following steps:

[0015] S1, dispersing CNC (cellulose nanocrystals) in deionized water to obtain aqueous phase A;

[0016] S2, dissolving the amino-functionalized polymer ligand and the fixative in the fragrance oil to obtain an oil phase B;

[0017] S3, mixing the oil phase B and the water phase A in proportion, and forming a uniform oil-in-water emulsion by high-speed shearing;

[0018] S4, adding the acidic aqueous solution of polyphenol compounds to the oil-in-water emulsion obtained in S3, shaking or stirring for a certain period of time to obtain a composite emulsion, so that the polyphenol substances are adsorbed on the emulsion interface;

[0019] S5, adding the dopamine hydrochloride aqueous solution to the composite emulsion obtained in S4, adjusting the solution to alkalinity, stirring and reacting for a certain period of time, and obtaining a composite polydopamine aromatic microcapsule suspension;

[0020] S6. Perform post-treatment to obtain composite polydopamine aromatic microcapsules.

[0021] The formation mechanism of the above composite polydopamine aromatic microcapsules is as follows:

[0022] First, negatively charged CNC and positively charged amino-functionalized polymer ligands self-assemble at the oil-water interface through electrostatic interaction to form a stable emulsion. Then, polyphenols are added to the emulsion. The catechol structure enables it to be effectively adsorbed on the surface of the emulsion droplets, thereby forming an elastic interfacial film and enhancing the strength of the droplet interface. Finally, dopamine monomers undergo oxidative self-polymerization in the outermost layer of the emulsion droplets to generate microcapsules with high adhesion and excellent mechanical properties, thereby successfully encapsulating aromatic substances.

[0023] The above preparation method is simple and efficient, simplifies the process flow, and has mild reaction conditions, which is suitable for large-scale production. The composite shell of this microcapsule not only has good biocompatibility and excellent adhesion properties, but also can regulate the mechanical properties of the microcapsule according to the needs of the application scenario. Specifically, the mechanical properties of the microcapsule can be effectively regulated by controlling the concentration of amino-functionalized polymer ligands, the concentration of polyphenol compounds and their deposition time, the concentration of dopamine hydrochloride and its polymerization time. This regulation mechanism realizes the mechanical stimulation response release of the microcapsule in different application scenarios, thereby greatly improving the utilization rate of aromatic oils, and has good application prospects.

[0024] As the preferred technical solution:

[0025] The method as described above, wherein the amino-functionalized polymer ligand is selected from one or more of NH2-PDMS-NH2, POSS-NH2 and PS-NH2;

[0026] The fixative is diethyl phthalate.

[0027] As described above, the pH of the solution is adjusted by adding tris(hydroxymethyl)aminomethane (Tris) to the solution.

[0028] In the method described above, the mass fraction of CNC in the aqueous phase A is 0.5-6 wt %;

[0029] The mass concentration of the amino-functionalized polymer ligand in the oil phase B is 0.1-20 mg / mL, and the volume fraction of the fixative in the oil phase B is 0.01-50%;

[0030] The mass concentration of the polyphenolic compound in the acidic aqueous solution of the polyphenolic compound is 0.01-10 mg / mL;

[0031] The mass concentration of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 5-30 mg / mL.

[0032] In the method as described above, in S3, the volume ratio of the oil phase B to the water phase A is 1:9 to 4:6;

[0033] The shear rate of the high-speed shearing is 6k~21k rpm, and the shearing time is 1~10 min.

[0034] In the method as described above, in S4, the pH of the acidic aqueous solution of polyphenol compounds is 3 to 6, and the oscillation or stirring time is 2 to 720 min;

[0035] In S5, the alkaline pH is 8-9, the stirring rate is 200-800 r / min, and the stirring reaction time is 12-36 h. The process does not require heating, and the reaction cannot be sealed.

[0036] In the method as described above, the post-treatment is to separate the microcapsules from the mixed reaction solution using a centrifuge, filter using a filter cloth, wash with deionized water until the solution is colorless and clear, and dry to obtain a black powder, thereby obtaining the composite polydopamine aromatic microcapsules.

[0037] The above technical solution is only a feasible technical solution of the present invention, and the protection scope of the present invention is not limited thereto. Those skilled in the art can reasonably adjust the specific design according to actual needs.

[0038] The above invention has the following advantages or beneficial effects:

[0039] (1) The composite polydopamine aromatic microcapsules of the present invention can encapsulate various aromatic oils, effectively solving the problem of aromatic oils being unstable during application. The adhesion performance is significantly better than that of conventional microcapsules. This is mainly due to the hydrogen bonds and electrostatic interactions formed between the wall material and the matrix, which enable the microcapsules to form a firm bond with the matrix. At the same time, the mechanical properties are good.

[0040] (2) The preparation method of the composite polydopamine aromatic microcapsules of the present invention adopts an in-situ deposition method, utilizing the oxidative self-polymerization reaction of dopamine under alkaline conditions to form the microcapsule wall material, without the need for adding monomers, initiators, etc., and without the need for sealing and heating;

[0041] (3) The preparation method of the composite polydopamine aromatic microcapsules of the present invention has simple process, high preparation efficiency, mild reaction conditions and the raw materials used are all biodegradable substances, which is more in line with the requirements of green environmental protection;

[0042] (4) The preparation method of the composite polydopamine aromatic microcapsules of the present invention can effectively regulate the mechanical properties of the microcapsules by controlling parameters such as the concentration of the amino-functionalized polymer ligand, the concentration of the polyphenol compound and its deposition time, the concentration of dopamine hydrochloride and its polymerization time. This regulation mechanism realizes the mechanical stimulation response release of the microcapsules in different application scenarios, thereby greatly improving the utilization rate of the aromatic oil, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention and its features, appearance and advantages will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings. The same reference numerals indicate the same parts in all the drawings. The drawings are not drawn to scale, and emphasis is placed on illustrating the subject matter of the present invention.

[0044] Figure 1 The microscope image (a), scanning electron microscope image (b) and Young's modulus distribution diagram (c) of the composite polydopamine aromatic microcapsules prepared in Example 1;

[0045] Figure 2 The microscope image (a), scanning electron microscope image (b) and Young's modulus distribution diagram (c) of the composite polydopamine aromatic microcapsules prepared in Example 2;

[0046] Figure 3 The scanning electron microscope images of the composite polydopamine aromatic microcapsule treated textiles prepared in Example 3 at different magnifications;

[0047] Figure 4 The scanning electron microscope images of the textiles treated with the composite polydopamine aromatic microcapsules prepared in Example 4 at different magnifications. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0049] Example 1

[0050] A method for preparing composite polydopamine aromatic microcapsules comprises the following steps:

[0051] S1. Preparation of aqueous phase: Weigh 1.0 wt% CNC (cellulose nanocrystals) and add it to water. Use an ultrasonic cell crusher at 600 W for 5 min to completely disperse it.

[0052] S2. Preparation of oil phase: 1 mg / mL NH2-PDMS-NH2 was dissolved in a mixture of 1.9 mL limonene and 0.1 mL diethyl phthalate, and the mixture was fully stirred with a magnetic stirrer at a speed of 450 rpm for 1 h.

[0053] S3, mixing the oil phase obtained in S2 with the water phase obtained in S1 at a ratio of 1 / 9 (v / v), and then shearing the mixture at 21k rpm for 3 min to obtain an oil-in-water fragrance emulsion;

[0054] S4. Add 2 mg / mL tannic acid to the above oil-aromatic emulsion, adjust the pH to 6 with Tris powder, vortex and oscillate for 2 minutes to mix evenly, and obtain a composite emulsion.

[0055] S5. Add 10 mg / mL dopamine hydrochloride to the above composite emulsion, adjust the pH to 8.5 with Tris powder, and polymerize at a stirring speed of 450 rpm for 24 h.

[0056] S6, performing post-treatment, centrifugal washing and drying to obtain composite polydopamine aromatic microcapsules.

[0057] Microscope images of the prepared composite polydopamine aromatic microcapsules are shown in Figure 1 (a) shows the scanning electron microscope image. Figure 1 (b) shows the distribution of Young's modulus measured by atomic force microscopy. Figure 1 (c) The particle size of the prepared composite polydopamine aromatic microcapsules is about 5-20 μm, and the regional average Young's modulus is 252 MPa.

[0058] Example 2

[0059] A method for preparing composite polydopamine aromatic microcapsules is basically the same as Example 1, except that the concentration of NH2-PDMS-NH2 in S2 is 10 mg / mL.

[0060] Microscope images of the prepared composite polydopamine aromatic microcapsules are shown in Figure 2. Figure 2 (a) shows the scanning electron microscope image. Figure 2 (b) shows the distribution of Young's modulus measured by atomic force microscopy. Figure 2 As shown in (c). When the concentration of NH2-PDMS-NH2 increases to 10 mg / mL, the particle size of the prepared composite polydopamine aromatic microcapsules is about 5-20 μm, and the mechanical properties are significantly enhanced, and the regional average Young's modulus can reach 950 MPa. Compared with the microcapsules prepared with 1 mg / mL NH2-PDMS-NH2 in Example 1, the mechanical properties are enhanced by about 4 times.

[0061] Example 3

[0062] A method for preparing composite polydopamine aromatic microcapsules is basically the same as Example 1, except that the oil phase composition in S2 is 10 mg / mL POSS-NH2 dissolved in 2 mL limonene; the shear rate in S3 is 12k rpm; the composite emulsion is prepared in S4 by magnetic stirring at 450 rpm for 5.5 h; the polymerization reaction stirring speed in S5 is 200 rpm, and the reaction time is 21 h. The obtained aromatic microcapsules are used to finish textiles, and the adhesion of the microcapsules is observed. The scanning electron microscope images at different magnifications are as follows: Figure 3 It is found that there are a large number of polydopamine aromatic microcapsules on the composite polydopamine aromatic microcapsules finished textiles.

[0063] Example 4

[0064] A method for preparing composite polydopamine aromatic microcapsules is basically the same as Example 3, except that the oil phase composition in S2 is 10 mg / mL NH2-PDMS-NH2 dissolved in 2 mL limonene; the composite emulsion in S4 is prepared by magnetic stirring at 450 rpm for 20 h. The prepared aromatic microcapsules are used to finish textiles, and the adhesion of the microcapsules is observed. The scanning electron microscope images at different magnifications are as follows: Figure 4 It was found that the composite polydopamine aromatic microcapsules also had good adhesion effect on textiles.

[0065] Example 5

[0066] A method for preparing composite polydopamine aromatic microcapsules is basically the same as that of Example 1, except that cinnamaldehyde is used to replace limonene in S2.

[0067] Example 6

[0068] A method for preparing composite polydopamine aromatic microcapsules is basically the same as that of Example 1, except that the volume ratio of the oil phase to the water phase in S3 is 2:8.

[0069] Example 7

[0070] A method for preparing composite polydopamine aromatic microcapsules is substantially the same as that of Example 1, except that the concentration of dopamine hydrochloride in S5 is 15 mg / mL.

[0071] In summary, the composite polydopamine aromatic microcapsules of the present invention can microencapsulate various aromatic oils, effectively solving the defect of instability of aromatic oils during application, and its adhesion performance is significantly better than that of traditional microcapsules. This is mainly due to the hydrogen bonds and electrostatic interactions formed between the wall material and the matrix, which enable the microcapsules to form a firm bond with the matrix, and at the same time, its mechanical properties are good; the preparation method adopts an in-situ deposition method, and utilizes the oxidative self-polymerization reaction of dopamine under alkaline conditions to form the microcapsule wall material, without the need for external monomers, initiators, etc., and without sealing and heating; the process is simple, the preparation efficiency is high, the reaction conditions are mild, and the raw materials used are all biodegradable substances, which is more in line with the requirements of green environmental protection; the mechanical properties of the microcapsules can be effectively regulated by controlling parameters such as the concentration of amino-functionalized polymer ligands, the concentration of polyphenol compounds and their deposition time, the concentration of dopamine hydrochloride and its polymerization time, and the regulation mechanism realizes the mechanical stimulation response release of the microcapsules in different application scenarios, thereby greatly improving the utilization rate of aromatic oils, and having good application prospects.

[0072] Those skilled in the art should understand that those skilled in the art can implement variations by combining the prior art and the above embodiments, which will not be described in detail here. Such variations do not affect the essential content of the present invention, and will not be described in detail here.

[0073] The above describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and the devices and structures that are not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention are still within the scope of protection of the technical solutions of the present invention.

Claims

1. A composite polydopamine aromatic microcapsule, characterized in that: The core material of the composite polydopamine aromatic microcapsule is aromatic oil, which is prepared by CNC encapsulating aromatic compounds to obtain Pickering emulsion, then depositing polyphenol compounds outside the emulsion droplets to form a film, and coating polydopamine on the outermost layer.

2. A composite polydopamine aromatic microcapsule according to claim 1, characterized in that: The aromatic oil is selected from one or more of limonene, linalool and cinnamaldehyde; The polyphenolic compound is selected from one or more of tannic acid, anthocyanin, resveratrol and quercetin.

3. A method for preparing a composite polydopamine aromatic microcapsule as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: S1, dispersing CNC in deionized water to obtain aqueous phase A; S2, dissolving the amino-functionalized polymer ligand and the fixative in the fragrance oil to obtain an oil phase B; S3, mixing the oil phase B and the water phase A in proportion, and forming a uniform oil-in-water emulsion by high-speed shearing; S4, adding the acidic aqueous solution of polyphenol compounds to the oil-in-water emulsion obtained in S3, shaking or stirring for a certain period of time to obtain a composite emulsion; S5, adding the dopamine hydrochloride aqueous solution to the composite emulsion obtained in S4, adjusting the solution to alkalinity, stirring and reacting for a certain period of time, and obtaining a composite polydopamine aromatic microcapsule suspension; S6. Perform post-treatment to obtain composite polydopamine aromatic microcapsules.

4. The method according to claim 3, characterized in that The amino-functionalized polymer ligand is selected from one or more of NH2-PDMS-NH2, POSS-NH2 and PS-NH2; The fixative is diethyl phthalate.

5. The method according to claim 3, characterized in that: The pH of the solution was adjusted by adding tris(hydroxymethyl)aminomethane to the solution.

6. The method according to claim 3, characterized in that The mass fraction of CNC in the aqueous phase A is 0.5-6 wt %; The mass concentration of the amino-functionalized polymer ligand in the oil phase B is 0.1-20 mg / mL, and the volume fraction of the fixative in the oil phase B is 0.01-50%; The mass concentration of the polyphenolic compound in the acidic aqueous solution of the polyphenolic compound is 0.01-10 mg / mL; The mass concentration of dopamine hydrochloride in the dopamine hydrochloride aqueous solution is 5-30 mg / mL.

7. The method according to claim 6, characterized in that In S3, the volume ratio of the oil phase B to the water phase A is 1:9 to 4:6; The shear rate of the high-speed shearing is 6k~21k rpm, and the shearing time is 1~10 min.

8. The method according to claim 6, characterized in that In S4, the pH of the acidic aqueous solution of polyphenol compounds is 3-6, and the oscillation or stirring time is 2-720 min; In S5, the alkaline pH is 8-9, the stirring rate is 200-800 r / min, and the stirring reaction time is 12-36 h.

9. The method according to claim 3, characterized in that: The post-treatment is to separate the microcapsules from the mixed reaction solution by using a centrifuge, filter by using a filter cloth, wash with deionized water until the solution is colorless and clear, and dry to obtain a black powder, that is, the composite polydopamine aromatic microcapsules.

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