An electrospun fiber mat, its preparation method and application

Abstract

The present invention provides an electrospun fiber mat, a preparation method thereof and an application thereof, relating to the technical field of composite materials. The preparation method of the electrospun fiber mat provided by the present invention comprises the following steps: mixing L-lactic acid, D-lactic acid, divalent metal oxide and an organic solvent to obtain a spinning solution; performing electrospinning on the spinning solution to obtain an electrospun fiber mat. The present invention can control the crystallinity of the electrospun fiber mat and improve the mechanical properties of the electrospun fiber mat.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and particularly relates to an electrospun fiber mat, a preparation method thereof, and an application thereof. Background Art

[0002] Polylactic acid (PLA) has good biodegradability and biocompatibility, excellent physical and mechanical properties, good processability, and is non-toxic to humans and the environment. Therefore, PLA materials have broad development prospects in replacing traditional polymer materials and have now been widely used in fields such as tissue engineering, drug controlled release, and environmental materials. However, due to the disadvantages of PLA such as high brittleness, slow crystallization rate, poor processing thermal stability, and poor mechanical properties, its application range is limited.

[0003] At an appropriate ratio of L-polylactic acid (PLLA) / D-polylactic acid (PDLA), PLLA and PDLA form stereocomplex polylactic acid (SC-PLA). The molecular chains of PLLA and PDLA are structurally complementary. The molecular chains of PLLA and PDLA interact and entangle through CH3···C═O. The packing of the molecular chains is more compact than that of the molecules in PLLA or PDLA (HC-PLA), and the intermolecular interaction is stronger. Therefore, SC-PLA has a higher melting point, better mechanical properties, and the biodegradability of the fiber is not damaged.

[0004] SC-PLA can be formed in a molten state or in the presence of a solvent. Therefore, there are many methods to obtain SC-PLA, such as injection molding, solution casting, and electrospinning. The current preparation methods cannot control the crystallinity of the fiber mat, and the mechanical properties need to be improved. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an electrospun fiber mat, a preparation method thereof, and an application thereof. The present invention can control the crystallinity of the electrospun fiber mat and improve the mechanical properties of the electrospun fiber mat.

[0006] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of an electrospun fiber mat, comprising the following steps:

[0008] Mix L-polylactic acid, D-polylactic acid, divalent metal oxide, and organic solvent to obtain a spinning solution;

[0009] Perform electrospinning on the spinning solution to obtain an electrospun fiber mat.

[0010] Preferably, the molecular weight of the D-polylactic acid is 10.0 - 80.0 kg / mol.

[0011] Preferably, the divalent metal oxide includes one or more of magnesium oxide, calcium oxide, zinc oxide, barium oxide, and strontium oxide.

[0012] Preferably, the mass of the divalent metal oxide accounts for 0.1-10% of the total mass of the L-polylactic acid and D-polylactic acid.

[0013] Preferably, the molecular weight of the L-polylactic acid is 40-160 kg / mol.

[0014] Preferably, the mass ratio of the L-polylactic acid to the D-polylactic acid is 7:3 to 3:7.

[0015] Preferably, the temperature of the electrospinning is room temperature; the pump feeding rate of the electrospinning is 0.001-0.05 mm / s; the voltage of the electrospinning is 12-13 kV.

[0016] Preferably, thermal processing is further included after the electrospinning.

[0017] The present invention provides an electrospun fiber mat prepared by the preparation method described in the above technical solution, including stereocomplex polylactic acid and a divalent metal oxide doped on the stereocomplex polylactic acid.

[0018] The present invention provides the application of the electrospun fiber mat described in the above technical solution in tissue engineering, drug controlled release, or environmental materials.

[0019] The present invention provides a method for preparing an electrospun fiber mat, including the following steps: mixing L-polylactic acid, D-polylactic acid, a divalent metal oxide, and an organic solvent to obtain a spinning solution; performing electrospinning on the spinning solution to obtain an electrospun fiber mat. The present invention controls the crystallinity of the electrospun fiber mat by adding a divalent metal oxide. The preparation method of the present invention is simple, and the crystallinity can be adjusted to meet the requirements of the material. The results of the examples show that when the mass fraction of added MgO is 5%, and at the same time when the molecular weight of PDLA is relatively low (10.0 kg / mol to 20.0 kg / mol), the crystallinity increases to 31%, the crystallization temperature increases, the melting temperature of SC-PLA slightly decreases, and the crystallinity further increases to 34% after thermal processing.

[0020] The electrospun fiber mat prepared by the present invention has excellent mechanical properties. The results of the examples show that when the molecular weight of PDLA is 10.0 kg / mol, the tensile strength significantly increases with the increase of the added MgO content. Description of the Drawings

[0021] Figure 1 For PDLA3 prepared in Example 3 1HNMR spectrum;

[0022] Figure 2 Morphology diagrams of electrospun fiber mats prepared in Comparative Example 4 and Example 8;

[0023] Figure 3 First heating DSC curves of fiber mats prepared in Example 5, 11, 17, 23 and Comparative Examples 3, 5, 7, 9;

[0024] Figure 4 DSC test result diagrams of fiber mats with different MgO contents;

[0025] Figure 5 Mechanical property test result diagrams of fiber mats prepared in Comparative Examples 1, 3, 5, 7, 9;

[0026] Figure 6 Mechanical property test result diagrams of fiber mats prepared in Comparative Example 2, Comparative Example 4, Example 8, Example 9 and Example 10;

[0027] Figure 7 Mechanical property test result diagrams of fiber mats prepared in Example 8, Example 14, Example 20 and Example 26. Detailed implementation manners

[0028] The present invention provides a method for preparing an electrospun fiber mat, comprising the following steps:

[0029] Mixing L-lactic acid oligomer, D-lactic acid oligomer, divalent metal oxide and organic solvent to obtain a spinning solution;

[0030] Performing electrospinning on the spinning solution to obtain an electrospun fiber mat.

[0031] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0032] The present invention mixes L-lactic acid oligomer, D-lactic acid oligomer, divalent metal oxide and organic solvent to obtain a spinning solution. In the present invention, the molecular weight of the L-lactic acid oligomer is preferably 40 - 160 kg / mol, more preferably 80 - 150 kg / mol. In the present invention, the molecular weight of the D-lactic acid oligomer is preferably 10.0 - 80.0 kg / mol, more preferably 20.0 - 40.0 kg / mol. The present invention controls the crystallinity of SC-PLA by changing the relative molecular mass of PDLA. In the present invention, the mass ratio of the L-lactic acid oligomer to the D-lactic acid oligomer is preferably 7:3 - 3:7, more preferably 1:1.

[0033] In the present invention, the preparation method of the right-handed polylactic acid preferably includes: mixing D-lactide (D-LA), polyethylene glycol (PEG), a solvent and a catalyst, and carrying out a polymerization reaction under anhydrous and anaerobic conditions to obtain the right-handed polylactic acid. In the present invention, the molecular weight of the polyethylene glycol is preferably 0.8 to 20 kg / mol, more preferably 4 to 10 kg / mol. In the present invention, the mass ratio of the D-lactide to the polyethylene glycol is preferably 4 to 29:1, more preferably 9 to 19:1. In a specific embodiment of the present invention, when the mass ratio of the D-lactide to the polyethylene glycol is 4:1, the molecular weight of the right-handed polylactic acid is 10.0 kg / mol; when the mass ratio of the D-lactide to the polyethylene glycol is 9:1, the molecular weight of the right-handed polylactic acid is 20.0 kg / mol; when the mass ratio of the D-lactide to the polyethylene glycol is 19:1, the molecular weight of the right-handed polylactic acid is 40.0 kg / mol; when the mass ratio of the D-lactide to the polyethylene glycol is 29:1, the molecular weight of the right-handed polylactic acid is 80.0 kg / mol. In the present invention, the solvent is preferably toluene; the mass-volume ratio of the D-lactide to toluene is preferably 4 to 14.5 g:20 mL, more preferably 1:4. In the present invention, the catalyst is preferably stannous octanoate (Sn(Oct)2); the mass of the catalyst is preferably 0.1 to 1 wt% of the total mass of the D-lactide and the polyethylene glycol, more preferably 0.2 wt%. In the present invention, the temperature of the polymerization reaction is preferably 110 to 135 °C, more preferably 130 °C; the time of the polymerization reaction is preferably 16 to 30 h, more preferably 24 h. The present invention preferably removes the solvent in the obtained polymerization reaction system after the polymerization reaction, adds chloroform to dissolve the product, then carries out precipitation with an anhydrous ethanol solution, and after precipitation, carries out vacuum drying to obtain the right-handed polylactic acid. In the present invention, the temperature of the vacuum drying is preferably 40 °C, and the time of the vacuum drying is preferably 72 h.

[0034] In the present invention, the divalent metal oxide preferably includes one or more of magnesium oxide, calcium oxide, zinc oxide, barium oxide and strontium oxide. In the present invention, the mass of the divalent metal oxide preferably accounts for 0.1 to 10% of the total mass of the left-handed polylactic acid and the right-handed polylactic acid, more preferably 5%.

[0035] In the present invention, the organic solvent preferably includes dichloromethane. In the present invention, the total concentration of the left-handed polylactic acid and the right-handed polylactic acid in the spinning solution is preferably 0.3 to 1.0 g / mL, more preferably 0.5 to 0.8 g / mL.

[0036] In the present invention, the temperature of the electrospinning is preferably room temperature; the pump feeding rate of the electrospinning is preferably 0.001 - 0.05 mm / s; the voltage of the electrospinning is preferably 12 - 13 kV. In a specific embodiment of the present invention, the pump feeding rate of the electrospinning is preferably 0.005 mm / s; the voltage of the electrospinning is preferably 12 kV

[0037] In the present invention, preferably, heat treatment is further included after the electrospinning. In the present invention, the temperature of the heat treatment is preferably 50 - 100 °C, more preferably 75 - 90 °C. In the present invention, the time of the heat treatment is preferably 0.5 - 4 h, more preferably 1 - 2 h. Through the heat treatment, the crystallinity of the electrospun fiber mat can be further improved in the present invention.

[0038] The present invention provides an electrospun fiber mat prepared by the preparation method described in the above technical solution, which includes stereocomplex poly(lactic acid) and divalent metal oxide doped on the stereocomplex poly(lactic acid).

[0039] The present invention provides the application of the electrospun fiber mat described in the above technical solution in tissue engineering, drug controlled release or environmental materials.

[0040] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] Table 1 Types and Sources of Raw Materials

[0042]

[0043]

[0044] Examples 1 - 4

[0045] Preparation of dextrorotatory poly(lactic acid): As shown in Table 2, D-LA and PEG were added into a reaction flask under anhydrous and anaerobic conditions, heated to 130 °C in an oil bath, 20 mL of toluene was used as a solvent, Sn(Oct)2 (the mass of Sn(Oct)2 was 0.2 wt% of the total mass of PEG and D-LA) was used as a catalyst, and the reaction was carried out for 24 h under anhydrous and anaerobic conditions; the toluene solvent was pumped out with a vacuum pump, 10 mL of chloroform was added to dissolve the product, and then precipitation was carried out with absolute ethanol according to the volume ratio of absolute ethanol to chloroform of 10:1; after precipitation, it was placed in a vacuum drying oven, and vacuum was pumped at 40 °C for 72 h to obtain dextrorotatory poly(lactic acid).

[0046] Table 2 Preparation Conditions of Dextrorotatory Poly(lactic Acid)

[0047] Example Number Right-handed polylactic acid D-LA, g PEG, g Molecular weight Example 1 PDLA1 4 1 10.0 kg / mol Example 2 PDLA2 9 1 20.0 kg / mol Example 3 PDLA3 9.5 0.5 40.0 kg / mol Example 4 PDLA4 14.5 0.5 80.0 kg / mol

[0048] Examples 5 - 7, Examples 11 - 13, Examples 17 - 19, Examples 23 - 25, Comparative Example 1, Comparative Example 3, Comparative Example 5, Comparative Example 7, Comparative Example 9

[0049] The right - hand - rotated polylactic acid was prepared by the method of Examples 1 - 4;

[0050] Preparation of electrospun fiber mat: As shown in Table 3, the right - hand - rotated polylactic acid was dissolved in dichloromethane to obtain a right - hand - rotated polylactic acid solution with a concentration of 0.5 g / mL; PLLA was dissolved in dichloromethane to obtain a left - hand - rotated polylactic acid solution with a concentration of 0.5 g / mL; 5 mL of the right - hand - rotated polylactic acid solution, 5 mL of the left - hand - rotated polylactic acid solution and MgO were mixed evenly to obtain a spinning solution; the spinning solution was electrospun at room temperature, the pump feeding rate was 0.005 mm / s, and the voltage was set at 12 kV to obtain an electrospun fiber mat.

[0051] Examples 8 - 10, Examples 14 - 16, Examples 20 - 22, Examples 26 - 30, Comparative Example 2, Comparative Example 4, Comparative Example 6, Comparative Example 8, Comparative Example 10

[0052] The right - hand - rotated polylactic acid was prepared by the method of Examples 1 - 4;

[0053] Preparation of electrospun fiber mat: As shown in Table 3, the right - hand - rotated polylactic acid was dissolved in dichloromethane to obtain a right - hand - rotated polylactic acid solution with a concentration of 0.5 g / mL; PLLA was dissolved in dichloromethane to obtain a left - hand - rotated polylactic acid solution with a concentration of 0.5 g / mL; 5 mL of the right - hand - rotated polylactic acid solution, 5 mL of the left - hand - rotated polylactic acid solution and MgO were mixed evenly to obtain a spinning solution; the spinning solution was electrospun at room temperature, the pump feeding rate was 0.005 mm / s, the voltage was set at 12 kV, and heat treatment was carried out at 75 °C for 2 h to obtain a heat - treated electrospun fiber mat.

[0054] The addition amount of MgO in Table 3 refers to the percentage of the mass of MgO in the total mass of the right - hand - rotated polylactic acid and the left - hand - rotated polylactic acid. In Example 29, MgO was adjusted to CaO, and in Example 30, MgO was adjusted to ZnO.

[0055] Table 3 Preparation conditions of electrospun fiber mat

[0056]

[0057]

[0058]

[0059] Test Case

[0060] (1) Figure 1 The PDLA3 prepared in Example 3 1 HNMR spectrum. The peak at 1.58ppm (a) is the absorption peak of methyl hydrogen in PDLA, the peak at 3.65ppm (b) is the peak of methylene in ethylene glycol, and the quartet at 5.16ppm (c) is the absorption peak of methine hydrogen in PDLA, proving that PDLA was synthesized. The relative molecular weight of all prepared PDLA was calculated by NMR, and the calculated results were consistent with the GPC data, indicating that PDLA of different molecular weights was successfully prepared.

[0061] The structures of PLLA and the prepared PDLA molecular chains are complementary, and the molecular chains of the two interact and entangle through CH3···C=O. The stacking of the molecular chains is more compact than that of the molecules in PLLA or PDLA (HC-PLA), and the intermolecular interactions are stronger.

[0062] (2) The morphology of the electrospun fiber felt prepared in Comparative Example 4 and Example 8 is shown in FIG. Figure 2 As shown. Figure 2 It can be seen that the membrane formed by directly mixing PDLA and PLLA for spinning has an obvious silk-like structure and is relatively loose; the membrane formed after adding MgO has no obvious silk-like structure, and the surface is relatively uniform and not loose.

[0063] (3) Figure 3 The single-temperature DSC curves of the fiber felts prepared in Examples 5, 11, 17, 23 and Comparative Examples 3, 5, 7, and 9.

[0064] The electrospun fiber felt obtained by spinning was subjected to DSC test, and the test conditions were as follows: the sample was heated from 25°C to 250°C at a heating rate of 10°C / min.

[0065] from Figure 3 It can be seen from the first heating curve that during the initial heating, the crystallinity of the material increases and the grain size gradually increases, resulting in a more obvious crystallization peak. For the fiber felt with the addition of MgO, the melting temperature decreases and the crystallization temperature increases. At the same time, when the molecular weight of PDLA is low (10.0kg / mol to 20.0kg / mol), the crystallinity increases from 27% to 31% and from 25% to 31%, respectively. The crystallinity increases significantly. The calculation results are shown in Table 4. The crystallinity can be further improved after heat treatment at 75°C for 2h.

[0066] The DSC test results of the electrospun fiber felts prepared in the examples and comparative examples are shown in Table 4.

[0067] Table 4 DSC test results of electrospun fiber mats prepared in examples and comparative examples

[0068]

[0069] (4) DSC test results of fiber mats with different MgO contents

[0070] The electrospun fiber mats obtained by spinning were subjected to DSC testing under the following conditions: The sample was heated from 25 °C to 250 °C at a heating rate of 10 °C / min, and the curve was recorded. As Figure 4 shown, according to this heating curve, it can be seen that as the MgO content increases, the melting temperature decreases, and the crystallinity increases from 28% under the condition of 1% MgO to 31% at 5% and 33% at 10%.

[0071] (5) The electrospun fiber mats obtained by spinning were subjected to mechanical property testing under the following conditions: The tensile rate was 50 mm / min, the width of the fiber mat was 1 cm, and the thickness was 0.1 mm.

[0072] Figure 5 Figure showing the mechanical property test results of the fiber mats prepared in Comparative Examples 1, 3, 5, 7, and 9. It can be seen from Figure 5 that when the molecular weight of PDLA is 10.0 kg / mol, its tensile strength is three times that of the fiber mat obtained by spinning pure PLLA, with an increase of 1.2 MPa. The tensile strengths of the fiber mats obtained by blending and spinning PDLA with other molecular weights and PLLA are also enhanced.

[0073] Figure showing the mechanical property test results of the fiber mats prepared in Comparative Example 2, Comparative Example 4, Example 8, Example 9, and Example 10 is as Figure 6 shown. It can be seen from Figure 6 that the tensile strength of H-PDLA1 / PLLA / MgO is greater than that of H-PDLA1 / PLLA, and as the MgO content increases, the tensile strength also gradually increases. When the MgO content is 1%, compared with H-PDLA1 / PLLA, the tensile strength only increases by 0.2 MPa. When the MgO content is increased to 5%, the tensile strength increases by 0.9 MPa compared with H-PDLA1 / PLLA. When the MgO content is 10%, the tensile strength increases by 1.6 MPa compared with H-PDLA1 / PLLA.

[0074] Figure showing the mechanical property test results of the fiber mats prepared in Example 8, Example 14, Example 20, and Example 26 is as Figure 7 shown. It can be seen from Figure 7It can be seen that when the molecular weight of PDLA is 10.0 kg / mol, the tensile strength of H-PDLA1 / PLLA / 5% MgO is the largest, far higher than that of H-PDLA2 / PLLA / 5% MgO, H-PDLA3 / PLLA / 5% MgO, and H-PDLA4 / PLLA / 5% MgO.

[0075] This invention is supported by the National Key Research and Development Program "Development of Polylactic Acid Fibers and Application of Products", project number: 2022YFB3704900, project name: Large-scale Preparation Technology of Polylactic Acid and One-step Industrial Demonstration of Key Monomer Lactide.

[0076] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing an electrospun fiber mat, the steps are as follows: Mixing L - polylactic acid, D - polylactic acid, divalent metal oxide and organic solvent to obtain a spinning solution; Performing electrospinning on the spinning solution to obtain an electrospun fiber mat; Performing heat treatment after the electrospinning; The molecular weight of the D - polylactic acid is 10.0 kg / mol; The divalent metal oxide is magnesium oxide, and the mass of the divalent metal oxide accounts for 5% of the total mass of L - polylactic acid and D - polylactic acid; The molecular weight of the L - polylactic acid is 80 - 150 kg / mol; The temperature of the heat treatment is 75 °C and the time is 2 h.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the L - polylactic acid to the D - polylactic acid is 7:3 - 3:

7.

3. The preparation method according to claim 1, wherein The temperature of the electrospinning is room temperature; the pump feeding rate of the electrospinning is 0.001 - 0.05 mm / s; the voltage of the electrospinning is 12 - 13 kV.

4. The electrospun fiber mat prepared by the preparation method according to any one of claims 1 - 3, comprising stereocomplex poly(lactic acid) and divalent metal oxide doped on the stereocomplex poly(lactic acid); The divalent metal oxide is magnesium oxide; The crystallinity of the electrospun fiber mat is 34%.

5. Use of the electrospun fiber mat according to claim 4 in tissue engineering, drug controlled release or environmental materials.

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