Hybrid mineral film as well as preparation method and application thereof

Abstract

The invention discloses a hybrid mineral thin film as well as a preparation method and application thereof. The hybrid mineral thin film comprises sodium alginate and a calcium-phosphorus oligomer in a mass ratio of 1: (0.8-1.5). The hybrid mineral film has good flexibility macroscopically and can adapt to complex deformation such as bending and stretching, meanwhile, a stable mineral network is kept on the microstructure, and the defects that a traditional film is fragile and difficult to process are effectively overcome. The preparation method of the hybrid mineral film is simple, has good process compatibility and industrialization potential, and is superior to the process limitation of an existing hydroxyapatite film high-temperature sintering or complex deposition method.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a hybrid mineral thin film, its preparation method, and its application. Background Technology

[0002] Plastics are widely used in retail, food packaging, and daily life due to their low cost, lightweight, durability, and ease of use, covering almost all commercial and household scenarios. However, the vast majority of plastic products on the market are still made from petrochemical resources (>98%), and their main chain structure generally contains stable carbon-carbon (CC) covalent bonds. This structure gives petrochemical plastics excellent mechanical properties and chemical stability, but it also makes them extremely difficult to decompose in the natural environment, allowing them to persist for decades or even centuries. This results in their long-term residues in soil, water, and the atmosphere, leading to the increasingly serious problem of "white pollution." Although biodegradable films based on natural polymers such as lignin and cellulose have been developed in recent years, they often suffer from weak mechanical properties and poor interfacial bonding, limiting their widespread application in packaging materials. On the other hand, mineral materials such as calcium phosphate have become potential alternatives to plastics due to their good biocompatibility and mechanical properties. However, the three-dimensional ionic network structure of traditional mineral materials results in high brittleness and a lack of flexibility, making them unsuitable for flexible film applications. Summary of the Invention

[0003] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a hybrid mineral thin film, a method for preparing the same, and its applications.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a hybrid mineral film comprising sodium alginate and calcium phosphate oligomer in a mass ratio of 1:(0.8-1.5).

[0005] In this invention, calcium phosphate oligomers (CPO) are produced via Ca... 2+ Cross-linking occurs through strong ionic and hydrogen bonds between the carboxyl groups (-COOH) and hydroxyl groups (-OH) in the sodium alginate (SA) chain. SA contains abundant and high-density carboxyl groups, resulting in numerous chemical bonds with calcium phosphate, significantly enhancing the cross-linking strength. Therefore, even with a higher proportion of calcium phosphate oligomers than sodium alginate, molecular-level compatibility and no phase separation are achieved. Furthermore, the introduction of rigid, linear calcium phosphate oligomer segments into the SA chain significantly reduces the flexibility of the hybrid mineral film and imparts mechanical properties characteristic of inorganic materials. Adjusting the mass ratio of calcium phosphate oligomers to sodium alginate allows for the regulation of its mechanical strength to meet different application requirements.

[0006] In some embodiments, the mass ratio of sodium alginate to calcium phosphate oligomer is 1:(0.8-1.5), such as 1:(0.9-1.4), 1:(1.0-1.3), 1:(1.1-1.2), etc.

[0007] In some embodiments, the calcium-phosphorus oligomers in the hybrid mineral film constitute 30%-45% by mass, such as 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, etc. In this invention, the mass percentage of calcium-phosphorus oligomers is measured using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0008] In some embodiments, the calcium phosphate oligomer has the structural formula shown in Formula I: Where n is the degree of aggregation.

[0009] In some implementations, n is any natural number from 1 to 5, such as 1, 2, 3, 4, 5.

[0010] In some embodiments, the calcium-phosphorus oligomer contains hydroxyapatite. In this invention, the calcium-phosphorus oligomer can be partially converted into hydroxyapatite, exhibiting a reactivity far exceeding that of traditional nanoparticles, thus enhancing the binding of the calcium-phosphorus oligomer to sodium alginate.

[0011] In some embodiments, the hydroxyapatite content in the calcium phosphate oligomer is 45-65%, such as 50-60%, 50-58%, etc.

[0012] In some embodiments, the sodium alginate and calcium phosphate oligomer are bonded together by ionic and hydrogen bonds.

[0013] In some embodiments, the hydroxyapatite in the hybrid mineral film is linearly oriented. In this invention, the linearly oriented ordered arrangement of hydroxyapatite can improve the mechanical strength and functional responsiveness of the material; the combination of sodium alginate with organic conductive and linearly oriented hydroxyapatite mineral crystals enables the hybrid mineral film to respond to external stimuli (such as pressure, heat, and electrical signals), realizing controllable information marking and erasing functions.

[0014] In some embodiments, the hydroxyapatite in the hybrid mineral film is arranged in anisotropic linear order.

[0015] In some embodiments, the surface contact angle of the hybrid mineral film is 40°-53°, such as 43°-52°, 45°-50°, etc. In this invention, the surface contact angle of the hybrid mineral film is measured using a water droplet contact angle tester.

[0016] In some embodiments, the surface roughness of the hybrid mineral film is 60-95 nm. In this invention, the surface roughness of the hybrid mineral film is measured by atomic force microscopy.

[0017] In some embodiments, the tensile strength of the hybrid mineral film is 55-80 MPa, such as 58-75 MPa.

[0018] In some embodiments, the elastic modulus of the hybrid mineral film is 2900-4000 MPa, such as 2950-3800 MPa.

[0019] A second aspect of the present invention provides a method for preparing the hybrid mineral thin film, comprising the following steps: Sodium alginate solution was mixed with calcium phosphate oligomer dispersion, and the mixture was stirred and reacted to obtain a composite slurry. The slurry is spread and dried to obtain the hybrid mineral film.

[0020] In some embodiments, the mass concentration of the sodium alginate solution is 15-35 mg / mL, such as 20-30 mg / mL, 22-28 mg / mL, etc.

[0021] In some embodiments, the concentration of the calcium phosphate oligomer dispersion is 1.0-4.0 wt%, such as 1.0-3.0 wt%, 1.5-2.5 wt%, etc.

[0022] In some embodiments, the reaction time of the stirring reaction is 1-5 hours, such as 2-4 hours.

[0023] In some embodiments, the preparation method of the calcium-phosphorus oligomer dispersion includes the following steps: adding an organic solvent containing a phosphorus source to an organic solvent system containing a calcium source and an organic amine stabilizer, stirring and reacting to obtain a calcium-phosphorus oligomer, and then dispersing it in water to obtain the calcium-phosphorus oligomer dispersion. In this invention, an organic amine stabilizer is used to regulate the calcium content in the organic solvent system. 2+ The reaction with phosphoric acid can enhance the reactivity of the product.

[0024] In some embodiments, the calcium source includes calcium chloride or its hydrates (such as dihydrates).

[0025] In some embodiments, the organic amine stabilizer includes triethylamine.

[0026] In some embodiments, the phosphorus source includes phosphoric acid.

[0027] In some embodiments, the organic solvent includes ethanol.

[0028] A third aspect of the present invention provides an application of the hybrid mineral film in packaging, electronic displays, agriculture, and medicine.

[0029] In some embodiments, the applications include packaging films, renewable labels, flexible electronic paper, agricultural water and fertilizer retention films, pesticide or fertilizer carrier films, wound protection films, controlled-release drug films, and in vivo implantable sensor encapsulation films.

[0030] The beneficial effects of this invention are: The hybrid mineral film of the present invention can respond to external stimuli (such as pressure, heat, and electrical signals) to achieve controllable information writing, and has broad application prospects in fields such as flexible electronic paper and renewable labels.

[0031] The hybrid mineral film of the present invention contains flexible sodium alginate and hydroxyapatite (HAP) crystals in calcium phosphate oligomers. It not only has good flexibility on a macroscopic scale, which can adapt to complex deformations such as bending and stretching, but also maintains a stable mineral network of HAP on a microscopic scale, effectively avoiding the disadvantages of traditional films being fragile and difficult to process.

[0032] The calcium phosphate oligomer of the hybrid mineral film of the present invention contains hydroxyapatite, which can achieve directional and ordered nanostructure arrangement, improve the mechanical strength and functional responsiveness of the material; it does not contain toxic metal ions or harmful chemical crosslinking agents, and has excellent environmental friendliness and biocompatibility, and can be used in scenarios with high requirements for biosafety, such as medical records and implantable sensors.

[0033] The method for preparing hybrid mineral thin films of the present invention is simple, has good process compatibility and industrialization potential, and is superior to the process limitations of existing high-temperature sintering or complex deposition methods for HAP thin films. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the hybrid mineral thin film preparation process in Example 1 of the present invention.

[0035] Figure 2 The XRD patterns of alcohol-phase CPO (E-CPO) powder and aqueous-phase CPO (W-CPO) powder in Example 1 of this invention are shown.

[0036] Figure 3 These are scanning electron microscope (SEM) images of the cross-sectional morphology of the SA films in Comparative Example 1, the CPO-SA films in Example 1, and the CPN-SA films in Comparative Example 2 of the present invention.

[0037] Figure 4 This is an elemental distribution diagram of the CPO-SA thin film in Example 1 of the present invention.

[0038] Figure 5This invention provides an analysis of the molecular-level interactions between CPO and SA. Figure 5 In the figure, 'a' represents the X-ray diffraction pattern of the SA film in Comparative Example 1, the CPN-SA film in Comparative Example 2, and the CPO-SA film in Example 1. Figure 5 In the figure, b represents the attenuated total internal reflection Fourier transform infrared spectra of the SA films in Comparative Example 1, CPN-SA films in Comparative Example 2, and CPO-SA films in Example 1. Figure 5 In this context, 'c' represents the Ca2p binding energy spectrum of the CPO powder in Example 1. Figure 5 In this diagram, d represents the Ca2p binding energy spectrum of the CPO-SA film in Example 1.

[0039] Figure 6 Analysis of the coordination state of Ca in the CPO-SA film in Example 1 of this invention; Figure 6 In the figure, 'a' represents the R-space experimental EXAFS data and fitting curves of CaO, W-CPO powder and CPO-SA film. Figure 6 In this context, 'b' represents the wavelet transform analysis of the CaO standard sample, W-CPO powder, and CPO-SA thin film, with the following parameters: R range: 0–5.0 Å, k range: 0–16.0 Å. -1 (Applicable to samples and standards); k has a weight of 2; Morlet wavelet function (κ = 8, σ = 1) is used as the mother wavelet to represent the overall distribution.

[0040] Figure 7 The film-forming mechanism of sodium alginate films; Figure 7 In this context, 'a' represents the sodium alginate molecular chain. Figure 7 In this context, b represents the unit cell structure of hydroxyapatite; Figure 7 In this context, 'c' represents the film-forming mechanism of sodium alginate films. Figure 7 In this context, d represents the film formation mechanism of the CPO-SA hybrid mineral film of this invention.

[0041] Figure 8 This invention relates to the effect of ink wettability on the writing quality of thin films. Figure 8 In the figure, 'a' represents the writing images of a ballpoint pen on the SA film in Comparative Example 1, the CPN-SA film in Comparative Example 2, and the CPO-SA film in Example 1. Figure 8 In the figure, b represents the surface morphology of the SA film in Comparative Example 1, the CPN-SA film in Comparative Example 2, and the CPO-SA film in Example 1. Detailed Implementation

[0042] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0043] Example 1 This embodiment prepares a hybrid mineral thin film, and the specific process is as follows: Preparation of calcium phosphate oligomer (CPO): Weigh 0.50-0.80 g of calcium chloride dihydrate (CaCl2·2H2O) and dissolve it in 100 mL of anhydrous ethanol to form a clear alcoholic solution. Add 40-50 mL of triethylamine (TEA) to this solution and react for 20-50 minutes under magnetic stirring. Subsequently, slowly add a phosphoric acid alcohol solution prepared by dissolving 0.50-0.60 g of phosphoric acid (H3PO4) in 200 mL of ethanol, and continue the reaction for 12 hours under stirring. After the reaction is complete, collect the white precipitate by centrifugation (4000-6000 rpm), wash it three times with ethanol to remove residual triethylamine, and obtain alcoholic phase CPO powder (E-CPO) by natural drying at room temperature.

[0044] The alcohol-phase CPO powder was washed twice with deionized water to remove residual ethanol. The resulting CPO precipitate was redispersed in 20 mL of deionized water to prepare a homogeneous slurry with a concentration of approximately 25 mg·mL⁻¹. -1 A CPO aqueous dispersion was obtained. It was then set aside.

[0045] The aqueous CPO dispersion was dried at 60°C for 12 hours to obtain aqueous CPO powder (W-CPO).

[0046] Preparation of hybrid mineral thin films: 20 mL of film with a concentration of approximately 25 mg·mL⁻¹ -1 A calcium phosphate oligomer (CPO) aqueous dispersion was mixed with 20 mL of 2.0 wt% SA aqueous solution and reacted under vigorous stirring for 3 hours to obtain a homogeneous composite slurry. 40 mL of this slurry was poured into two separate petri dishes and allowed to dry at 25 °C until a composite film formed and could be peeled off completely.

[0047] Figure 1 A schematic diagram showing the process of preparing hybrid mineral thin films is displayed.

[0048] Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) Testing: The elemental mass fractions of the prepared samples were determined using a 720ES axial observation full-spectrum direct-reading ICP-OES system (Agilent Technologies, USA). The plasma gas flow rate was set to 12.0 L / min. -1 Each sample was measured three times.

[0049] ICP-OES analysis revealed that W-CPO contained 33.161 wt% Ca and 18.909 wt% P, while E-CPO contained 26.616 wt% Ca and 19.915 wt% P.

[0050] The CPO-SA membrane contains 32.36% sodium alginate, 30.49% water, and a high inorganic content of 37.15%, which is much higher than that of conventional composite materials.

[0051] Example 2 This embodiment prepares a hybrid mineral thin film, and the specific process is as follows: Calcium-phosphorus oligomers were prepared according to Example 1.

[0052] Preparation of hybrid mineral thin films: 10 mL of film with a concentration of approximately 25 mg·mL⁻¹ -1 A calcium phosphate oligomer (CPO) aqueous dispersion was mixed with 20 mL of 2.0 wt% SA aqueous solution and reacted under vigorous stirring for 3 hours to obtain a homogeneous composite slurry. 30 mL of this slurry was poured into two separate petri dishes and allowed to stand and dry at 25 °C until a composite film formed and could be peeled off completely.

[0053] Comparative Example 1 A sodium alginate film was prepared in this comparative example. The specific process is as follows: 20 mL of a 2.0 wt% sodium alginate aqueous solution was poured directly into a petri dish and allowed to dry naturally at 25°C. After the water was completely evaporated, a sodium alginate film that could be peeled off as a whole was obtained.

[0054] Comparative Example 2 A composite thin film was prepared in this comparative example, and the specific process is as follows: Preparation of calcium phosphate nanoparticles (CPN): 0.70-0.80 g of calcium chloride dihydrate (CaCl2·2H2O) was dissolved in 100 mL of ethanol to form a clear solution. A phosphoric acid solution prepared by dissolving 0.50-0.68 g of phosphoric acid (H3PO4) in 200 mL of ethanol was then added dropwise to the above solution, and the reaction was carried out under magnetic stirring for 12 hours. After the reaction was completed, the white precipitate was collected by centrifugation at 6000 rpm and washed three times with deionized water to remove residual reactants. The obtained precipitate was then redispersed in 20 mL of deionized water to obtain a uniform calcium phosphate nanoparticle dispersion with a concentration of approximately 25 mg·mL⁻¹. -1 ,spare.

[0055] Preparation of composite film (CPN-SA film): 20 mL of film with a concentration of approximately 25 mg·mL⁻¹ -1A calcium phosphate nanoparticle (CPN) aqueous dispersion was mixed with 20 mL of 2.0 wt% SA aqueous solution and reacted under vigorous stirring for 3 hours to obtain a homogeneous composite slurry. 40 mL of this slurry was poured into two separate petri dishes and allowed to stand and dry at 25 °C until a composite film formed and could be completely peeled off.

[0056] Test case This experimental example tests the properties of the films prepared in the examples and comparative examples. The specific process is as follows: Figure 2 The X-ray diffraction (XRD) patterns of alcohol-phase CPO (E-CPO) powder and aqueous-phase CPO (W-CPO) powder are shown.

[0057] Based on the aforementioned ICP-OES test results, it can be seen that the main component of E-CPO is CaHPO4; the main component of W-CPO is a mixture of hydroxyapatite and CaPO4, of which the content of hydroxyapatite is 53.73% (calculated based on the Ca / P ratio).

[0058] Figure 3 Scanning electron microscopy (SEM) images of the cross-sectional morphology of SA, CPO-SA, and CPN-SA films are shown. It can be seen that the CPO-SA film possesses a continuous and dense cross-sectional structure, similar to that of the pure SA film, indicating good interfacial compatibility between the inorganic phase and the polymer.

[0059] Figure 4 The elemental distribution (EDS) diagram of the CPO-SA thin film is shown. It can be seen that the Ca, P, C, and O elements in the CPO-SA film are uniformly distributed with no obvious phase separation, which is far superior to the traditional CPN-SA composite film.

[0060] Figure 5 The molecular-level interaction analysis between CPO and SA is presented; Figure 5 In the figure, 'a' represents the X-ray diffraction (XRD) patterns of SA, CPN-SA, and CPO-SA thin films. Figure 5 In the figure, b represents the attenuated total internal reflection Fourier transform infrared (ATR-FTIR) spectra of SA, CPN-SA, and CPO-SA thin films; Figure 5 In the figure, c represents the Ca2p binding energy spectrum (XPS) of CPO powder; Figure 5 In the diagram, d represents the Ca2p binding energy spectrum of the CPO-SA thin film.

[0061] It can be seen that characteristic hydroxyapatite diffraction peaks exist in the CPO-SA film, and the preferred orientation of the (211) plane is significantly enhanced, suggesting that the inorganic phase exhibits anisotropic linear arrangement structure, and a linear inorganic crystal structure is formed in the CPO-SA film. The FTIR spectrum shows a shift in the OH absorption peak and a shift in the COC characteristic peak, indicating that CPO passes through Ca... 2+ The SA molecule forms a strong ionic bond and a hydrogen bond with the carboxyl group (-COOH) and hydroxyl group (-OH), resulting in a decrease in the Ca2p binding energy. Figure 5 b in Figure 5 (d) helps to form a stable and compact organic-inorganic synergistic network structure, which is different from traditional CaP nanoparticles that only interact with SA through physical mixing.

[0062] Figure 6 The coordination state analysis of Ca in CPO-SA thin films is presented; Figure 6 In the figure, 'a' represents the R-space experimental EXAFS data and fitting curves of CaO, W-CPO powder and CPO-SA film. Figure 6 In this context, 'b' represents the wavelet transform analysis of the CaO standard sample, W-CPO powder, and CPO-SA thin film, with the following parameters: R range: 0–5.0 Å, k range: 0–16.0 Å. -1 (Applicable to both samples and standard samples); k has a weight of 2; Morlet wavelet function (κ = 8, σ = 1) is used as the mother wavelet to represent the overall distribution.

[0063] It can be seen that the Ca-Ca coordination number in the CPO-SA membrane is 2.7 (far lower than the 12 of conventional hydroxyapatite), which is close to the ideal linear chain structure. This indicates that the inorganic segments have exhibited a short-range linear structure, supporting the construction of a hybrid model of "rigid linear framework + flexible polymer chain".

[0064] Figure 7 The film-forming mechanism of sodium alginate films. Figure 7 In this context, 'a' represents the sodium alginate molecular chain. Figure 7 In the figure, b represents the cell structure of hydroxyapatite. Figure 7 In this context, 'c' represents the film-forming mechanism of sodium alginate films. Figure 7 In this context, d represents the film formation mechanism of the CPO-SA hybrid mineral film.

[0065] Figure 8 The effect of ink wettability on the writing quality of thin films; Figure 8 In the figure, 'a' represents the writing image of a ballpoint pen on SA, CPN-SA, and CPO-SA films; Figure 8 b represents the surface morphology of SA, CPN-SA, and CPO-SA films (detected by atomic force microscopy, AFM).

[0066] Water droplet contact angle tests showed that the contact angle of the CPO-SA film surface was 48.8°, which was significantly reduced compared to the SA film (55.6°), indicating that it has stronger wettability. Atomic force microscopy (AFM) analysis showed that the surface roughness of the CPO-SA film was 78.33±14.15nm, which was much higher than that of the SA film (7.01±0.17 nm), improving the adhesion and diffusion of ink. In actual writing tests, the CPO-SA film surface can be directly used with water-based pens for smooth writing, with deep ink marks and clear lines, and its performance is superior to that of the traditional CPN-SA composite film.

[0067] Mechanical property testing: Tensile tests were conducted using a UMT-4103 mechanical testing instrument (SANS Shenzhen, USA). All samples were uniformly processed into thin films (14 mm wide, 30 mm long, and 0.035 mm thick), and tensile tests were performed at a rate of 2 mm / min. The mechanical property data were taken as the average of three samples, and the elastic modulus was determined based on the slope of the linear segment of the stress-strain curve.

[0068] The tensile strength of the CPO-SA film reached 65.79±7.68 MPa, which is significantly improved compared with the pure SA film (56.74±12.44 MPa); the elastic modulus was as high as 3260.34±265.30 MPa, which is about three times that of the pure SA film (981.87±167.24 MPa); at the same time, the elongation at break of the CPO-SA film decreased significantly, indicating that its mechanical behavior is closer to that of inorganic materials, suggesting that the inorganic phase in the hybrid structure is a continuous rigid skeleton.

[0069] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A hybrid mineral thin film, characterized in that: It includes sodium alginate and calcium phosphate oligomers in a mass ratio of 1:(0.8-1.5).

2. The hybrid mineral thin film according to claim 1, characterized in that: In the hybrid mineral film, the calcium-phosphorus oligomer accounts for 30%-45% by mass.

3. The hybrid mineral thin film according to claim 1, characterized in that: The structural formula of the calcium-phosphorus oligomer is shown in Formula I: Where n is the degree of aggregation.

4. The hybrid mineral thin film according to claim 1, characterized in that: The calcium phosphate oligomer contains hydroxyapatite.

5. The hybrid mineral thin film according to claim 1, characterized in that: The sodium alginate and calcium phosphate oligomer are bonded together by ionic and hydrogen bonds.

6. The hybrid mineral thin film according to claim 4, characterized in that: In the hybrid mineral film, hydroxyapatite is arranged in a linear orientation.

7. The hybrid mineral thin film according to claim 1, characterized in that: The surface contact angle of the hybrid mineral film is 40°-53°; and / or, the surface roughness of the hybrid mineral film is 60-95 nm; and / or, the tensile strength of the hybrid mineral film is 55-80 MPa; and / or, the elastic modulus of the hybrid mineral film is 2900-4000 MPa.

8. A method for preparing a hybrid mineral thin film according to any one of claims 1-7, characterized in that: Includes the following steps: Sodium alginate solution was mixed with calcium phosphate oligomer dispersion, and the mixture was stirred and reacted to obtain a composite slurry. The slurry is spread and dried to obtain the hybrid mineral film.

9. The method for preparing hybrid mineral thin films according to claim 8, characterized in that: The preparation method of the calcium-phosphorus oligomer dispersion includes the following steps: adding an organic solvent containing a phosphorus source to an organic solvent system containing a calcium source and an organic amine stabilizer, stirring and reacting to obtain a calcium-phosphorus oligomer, and then dispersing it in water to obtain the calcium-phosphorus oligomer dispersion.

10. The application of the hybrid mineral film according to any one of claims 1-7 in packaging, electronic display, agriculture, and medical applications.

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