PDDA / PSS / BC exchange membrane and preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, and discloses a PDDA / PSS / BC exchange membrane and a preparation method and application thereof, the PDDA / PSS / BC exchange membrane comprises a bacterial cellulose membrane and a multi-layer PDDA / PSS composite membrane loaded on the bacterial cellulose membrane; the PDDA / PSS composite membrane comprises a poly (diallyldimethylammonium chloride) membrane and a poly (sodium 4-styrenesulfonate) membrane loaded on the poly (diallyldimethylammonium chloride) membrane. The PDDA / PSS / BC exchange membrane has good hydrophilicity, chemical stability and excellent mechanical properties, and has potential application value in the field of preparation of high-performance fuel cell membranes.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a PDDA / PSS / BC exchange membrane and a preparation method and application thereof. Background Art

[0002] With the rapid development of new energy, a large number of refractory polymer ion exchange membrane materials have emerged, but they pose significant environmental risks. Consequently, research and development of biodegradable biomass-based ion exchange membranes has spurred significant interest. For example, a new technology for preparing membranes for photodegradable microbial fuel cells has been developed using surface-functionalized electrogenic bacteria. However, the intrinsic conductivity of these biomass-based membrane materials is very low, severely restricting transmembrane electron transfer within the biomembrane and significantly increasing the charge transfer impedance at the biomass-based bacteria-electrode interface. Recently, researchers have successfully fabricated a photoresponsive bioanode by alternately depositing conductive gold (Au) nanoparticles and semiconductor cadmium sulfide (CdS) nanoparticles on the surface of Escherichia coli. This Au / CdS / Au sandwich structure generates a significant photocurrent response while maintaining a baseline biocurrent density. The outer layer forms a continuous conductive network, establishing a cooperative transport channel for bioelectrons and photogenerated CdS electrons. This cell surface modification technique has been widely used in light-assisted microbial fuel cells.

[0003] However, the above-mentioned biomass-based fuel cell membranes currently have insufficient mechanical properties and low ion transport capabilities, which means that it is difficult to form self-supporting fuel cell membrane materials with high electrical conductivity. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of biomass-based fuel cell membranes being difficult to self-support and having low conductivity in the prior art, and to provide a PDDA / PSS / BC exchange membrane and its preparation method and application. The PDDA / PSS / BC exchange membrane has good hydrophilicity, chemical stability and excellent mechanical properties, and has potential application value in the field of high-performance fuel cell membrane preparation.

[0005] In order to achieve the above object, the present invention provides a PDDA / PSS / BC exchange membrane, wherein the PDDA / PSS / BC exchange membrane comprises a bacterial cellulose membrane and a multilayer PDDA / PSS composite membrane supported on the bacterial cellulose membrane;

[0006] The PDDA / PSS composite membrane comprises a polydiallyldimethylammonium chloride membrane and a poly(sodium 4-styrenesulfonate) membrane supported on the polydiallyldimethylammonium chloride membrane.

[0007] The PDDA / PSS / BC exchange membrane of the present invention has a polymer film structure of a dense cortex and a porous fiber mesh layer. A multilayer PDDA / PSS composite membrane is formed on a bacterial cellulose membrane (BC) by layer-by-layer self-assembly, so that the PDDA / PSS / BC exchange membrane not only has high conductivity but also has good mechanical properties. Preferably, the tensile strength of the PDDA / PSS / BC exchange membrane is 80 to 160 MPa and the conductivity is 20 to 100 mS / cm.

[0008] Preferably, the number of layers of the PDDA / PSS composite membrane is 2 to 16; further preferably, the number of layers of the PDDA / PSS composite membrane is 8 to 10.

[0009] The bacterial cellulose membrane in the present invention is commercially available from Guilin Qihong Technology Co., Ltd., and is specifically prepared by fermentation of Gluconobacter, the diameter of which is 50 to 100 nm and the length is 10 to 20 μm; and the bacterial cellulose membrane contains hydroxyl groups.

[0010] A second aspect of the present invention provides a method for preparing the above-mentioned PDDA / PSS / BC exchange membrane, comprising the following steps:

[0011] The bacterial cellulose membrane is cleaned, then placed in an alkaline solution for purification, and then washed to obtain a treated bacterial cellulose membrane;

[0012] The treated bacterial cellulose membrane is subjected to multiple PDDA / PSS composite membrane assembly treatments to obtain a composite exchange membrane; the PDDA / PSS composite membrane assembly treatment comprises: placing the treated bacterial cellulose membrane in a polydiallyldimethylammonium chloride solution for polydiallyldimethylammonium chloride self-assembly, washing the membrane, placing the membrane in a poly(sodium 4-styrene sulfonate) solution for poly(sodium 4-styrene sulfonate) self-assembly, and then washing the membrane;

[0013] The composite exchange membrane is freeze-dried to obtain a PDDA / PSS / BC exchange membrane.

[0014] Among them, before assembling the PDDA / PSS composite membrane on the bacterial cellulose membrane, the bacterial cellulose membrane needs to be cleaned in advance to remove surface impurities and other pollutants, and then placed in an alkaline solution for purification to fully activate the hydroxyl groups in the bacterial cellulose membrane, which is helpful for subsequent assembly operations. After the purification operation is completed, the surface is repeatedly rinsed with deionized water until the rinse liquid is neutral, which is used to remove excess alkaline solution to obtain the treated bacterial cellulose membrane.

[0015] Furthermore, the specific operation of cleaning the bacterial cellulose membrane includes: placing the bacterial cellulose membrane in water (the amount of water used is sufficient to ensure that the bacterial cellulose membrane is completely immersed), and then stirring at 20-40° C. for 1-48 hours, wherein the stirring speed is 50-900 rpm.

[0016] Preferably, the concentration of the alkaline solution is 0.05 to 1 mol / L, further 0.08 to 0.9 mol / L; in a specific embodiment, the concentration of the alkaline solution is 0.1 mol / L.

[0017] Specifically, the amount of the alkaline solution used is sufficient to ensure that the bacterial cellulose membrane is completely immersed.

[0018] Wherein, the alkaline agent in the alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water; further, the alkaline agent in the alkaline solution is sodium hydroxide and / or potassium hydroxide, and further, the alkaline agent in the alkaline solution is sodium hydroxide.

[0019] In a preferred embodiment, the purification operation includes: stirring at 20-100°C for 1-48 hours, wherein the stirring speed is 50-900 rpm; further preferably, the purification operation includes: stirring at 20-50°C for 16-30 hours, wherein the stirring speed is 500-700 rpm; further, the purification operation includes: stirring at 30-40°C for 20-24 hours, wherein the stirring speed is 550-650 rpm.

[0020] In the present invention, in order to ensure that a PDDA / PSS / BC exchange membrane with a target number of layers can be obtained and achieve better performance, the treated bacterial cellulose membrane is preferably subjected to 2 to 16 times of assembly of a PDDA / PSS composite membrane treatment; further, the treated bacterial cellulose membrane is subjected to 8 to 10 times of assembly of a PDDA / PSS composite membrane treatment; and as the number of assembly layers increases, the mechanical properties and electrical conductivity of the membrane are improved.

[0021] In the present invention, polydiallyldimethylammonium chloride (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) are preferably used for self-assembly treatment. Polydiallyldimethylammonium chloride is a cationic compound, and poly(sodium 4-styrenesulfonate) is an anionic compound. Both are strong polyelectrolytes and can be completely ionized in aqueous solutions with a pH value of 0 to 14. They have a wide range of applications. Electrostatic attraction is used to spontaneously combine polycations and polyanionic compounds on a substrate. Layer-by-layer self-assembly technology is used to form a PDDA / PSS / BC exchange membrane with a complete structure, stable performance and strong ion transport capacity. In addition, more hydrophilic positive and negative ions can be introduced, which is beneficial to improving the anion transport capacity of the PDDA / PSS / BC exchange membrane. Multilayer self-assembly introduces more polyelectrolytes, which is beneficial to increasing the water content of the PDDA / PSS / BC exchange membrane and improving the ion transport capacity, thereby significantly improving the mechanical properties and conductivity of the PDDA / PSS / BC exchange membrane.

[0022] In the present invention, the concentration of the polydiallyldimethylammonium chloride solution is 0.01 to 3 mg / mL, and more preferably 0.05 to 2 mg / mL.

[0023] Specifically, the amount of the polydiallyldimethylammonium chloride solution used is sufficient to completely immerse the membrane.

[0024] The self-assembly operation of the polydiallyldimethylammonium chloride comprises: stirring at 20 to 40° C. for 1 to 48 hours, wherein the stirring speed is 50 to 900 rpm; further preferably, the self-assembly operation of the polydiallyldimethylammonium chloride comprises: stirring at 25 to 40° C. for 10 to 30 hours, wherein the stirring speed is 500 to 700 rpm.

[0025] In a specific embodiment of the present invention, after the self-assembly of polydiallyldimethylammonium chloride is completed, it is repeatedly washed with deionized water 3 to 5 times, preferably 4 to 5 times, to remove residual reagents, and then placed in a poly(sodium 4-styrene sulfonate) solution for poly(sodium 4-styrene sulfonate) self-assembly.

[0026] In a further preferred embodiment of the present invention, the concentration of the poly(sodium 4-styrene sulfonate) solution is 0.01 to 3 mg / mL; preferably 0.05 to 2 mg / mL.

[0027] In a specific embodiment, the amount of poly (sodium 4-styrene sulfonate) solution used is sufficient to completely immerse the membrane.

[0028] The self-assembly operation of poly(sodium 4-styrene sulfonate) comprises: stirring at 20-40° C. for 1-48 hours, wherein the stirring speed is 50-900 rpm; further preferably, the self-assembly operation of poly(sodium 4-styrene sulfonate) comprises: stirring at 25-40° C. for 10-30 hours, wherein the stirring speed is 500-700 rpm.

[0029] In the specific operations of the self-assembly of polydiallyldimethylammonium chloride and poly(sodium 4-styrenesulfonate), a certain self-assembly time is required to allow sufficient electrostatic adsorption of the polycation and the polyanion, and therefore the self-assembly time needs to be controlled within the corresponding range.

[0030] In a specific embodiment of the present invention, after the self-assembly of poly(sodium 4-styrene sulfonate) is completed, it is washed repeatedly with deionized water for 3 to 5 times, preferably 4 to 5 times, to remove residual reagents.

[0031] In the present invention, the freeze-drying conditions include: a time of 4 to 72 hours and a temperature of -10 to -50°C.

[0032] In a specific embodiment, the freeze-drying time is 48 hours.

[0033] The present invention first activates the bacterial cellulose membrane under alkaline conditions to obtain abundant hydroxyl groups (-OH), which facilitates sufficient electrostatic adsorption with the strong polyelectrolyte polycationic compound polydiallyldimethylammonium chloride. Then, it is placed in a certain concentration of a strong polyelectrolyte polycationic compound polydiallyldimethylammonium chloride solution to fully complex and form a positive ion layer. Subsequently, it is placed in a certain concentration of a strong polyelectrolyte polyanionic compound poly(sodium 4-styrenesulfonate) solution, and electrostatic attraction is used to spontaneously combine the polycationic and polyanionic compounds on the substrate, thereby forming a PDDA / PSS / BC exchange membrane with a complete structure, stable performance and strong ion transmission capacity. This PDDA / PSS / BC exchange membrane has good chemical stability and excellent mechanical properties, and has potential application value in the field of high-performance fuel cell membrane preparation.

[0034] A third aspect of the present invention provides an application of the above-mentioned PDDA / PSS / BC exchange membrane in a fuel cell membrane.

[0035] The PDDA / PSS / BC exchange membrane described in the present invention has a main structure of bacterial cellulose membrane, which has the characteristics of easy biodegradability, excellent hydrophilicity, and rich hydroxyl functional groups; after purification and electrostatic adsorption, it has rich PDDA, PSS and strong ion transmission performance, which makes it easy to prepare a membrane with easy biodegradability, excellent mechanical properties and high hydrophilicity. It can be used as a high-performance anion exchange film material, providing a potential polymer material for fuel cell membranes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is BC in step (1) of Example 1, (PDDA / PSS)2 / BC in step (3), (PDDA / PSS)4 / BC in Example 2, (PDDA / PSS)6 / BC in Example 3, (PDDA / PSS)8 / BC in Example 4, and (PDDA / PSS) in Example 5. 10 / FTIR test results of BC;

[0037] Figure 2 It is BC in step (1) of Example 1, (PDDA / PSS)2 / BC in step (3), (PDDA / PSS)4 / BC in Example 2, (PDDA / PSS)6 / BC in Example 3, (PDDA / PSS)8 / BC in Example 4, and (PDDA / PSS) in Example 5. 10 / BC XRD test results diagram;

[0038] Figure 3 This is a scanning electron microscope image of the cross section of BC in step (1) of Example 1;

[0039] Figure 4 This is a scanning electron microscopy image of the cross section of (PDDA / PSS)2 / BC in step (3) of Example 1;

[0040] Figure 5 is a scanning electron microscopy image of the cross section of (PDDA / PSS)4 / BC in Example 2;

[0041] Figure 6 is a scanning electron microscopy image of the cross section of (PDDA / PSS)6 / BC in Example 3;

[0042] Figure 7 is a scanning electron microscopy image of the cross section of (PDDA / PSS)8 / BC in Example 4;

[0043] Figure 8 is (PDDA / PSS) in Example 5 10 / Scanning electron microscope results of the cross section of BC;

[0044] Figure 9 Graph showing the tensile strength results of BC in step (1) of Example 1, (PDDA / PSS)2 / BC in step (3), (PDDA / PSS)4 / BC in Example 2, (PDDA / PSS)6 / BC in Example 3, and (PDDA / PSS)8 / BC in Example 4;

[0045] Figure 10 It is BC in step (1) of Example 1, (PDDA / PSS)2 / BC in step (3), (PDDA / PSS)4 / BC in Example 2, (PDDA / PSS)6 / BC in Example 3, (PDDA / PSS)8 / BC in Example 4, and (PDDA / PSS) in Example 5. 10 / BC conductivity results diagram;

[0046] Figure 11 This is the contact angle result diagram of BC in step (1) of Example 1;

[0047] Figure 12 This is the contact angle result of (PDDA / PSS)2 / BC in step (3) of Example 1;

[0048] Figure 13 This is the contact angle result diagram of (PDDA / PSS)4 / BC in Example 2;

[0049] Figure 14 This is the contact angle result diagram of (PDDA / PSS)6 / BC in Example 3;

[0050] Figure 15 This is the contact angle result diagram of (PDDA / PSS)8 / BC in Example 4;

[0051] Figure 16 is (PDDA / PSS) in Example 5 10 / BC contact angle results. DETAILED DESCRIPTION

[0052] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0053] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0054] In addition, the technical solutions between the various embodiments provided by the present invention can be combined with each other, but they must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0055] The present invention will be described in detail below through examples. The experimental methods in the following examples, unless otherwise specified, are conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available (the bacterial cellulose membrane containing hydroxyl groups was purchased from Guilin Qihong Technology Co., Ltd.).

[0056] Example 1

[0057] (1) Cutting a bacterial cellulose membrane of 8 cm × 8 cm, placing it in 1 L of deionized water, and cleaning it with magnetic stirring at 25 ° C for 24 h to remove surface impurities, wherein the stirring speed is 600 rpm. After cleaning, taking it out and placing it in 0.1 mol / L NaOH solution for full purification. The purification operation includes: stirring at 40 ° C for 24 h, wherein the stirring speed is 600 rpm. After the purification operation is completed, the surface is repeatedly rinsed with deionized water until the rinse solution is neutral, and the treated bacterial cellulose membrane is obtained, which is recorded as BC;

[0058] (2) Weigh 0.1 g of PDDA solution and PSS solution with a concentration of 20 wt % respectively, place them in two 200 mL clean beakers, dilute them to 100 mL with deionized water, and stir them with magnetic force for 30 min to obtain 0.2 mg / mL PDDA solution and 0.2 mg / mL PSS solution; the treated bacterial cellulose membrane obtained in step (1) is subjected to two PDDA / PSS composite membrane assembly processes to obtain a composite exchange membrane; the PDDA / PSS composite membrane assembly process includes: placing the treated bacterial cellulose membrane in a 0.2 mg / mL PDDA solution; Performing self-assembly of polydiallyldimethylammonium chloride, wherein the self-assembly of polydiallyldimethylammonium chloride includes: stirring at 30° C. for 20 hours, wherein the stirring speed is 600 rpm; after the self-assembly of polydiallyldimethylammonium chloride is completed, taking out with tweezers and repeatedly rinsing with clean deionized water 5 times; and then placing in a PSS solution with a concentration of 0.2 mg / mL to perform self-assembly of poly (sodium 4-styrene sulfonate); the self-assembly of poly (sodium 4-styrene sulfonate) includes: stirring at 30° C. for 20 hours, wherein the stirring speed is 600 rpm; after the self-assembly of poly (sodium 4-styrene sulfonate) is completed, taking out with tweezers and repeatedly washing with deionized water 5 times;

[0059] (3) freeze-drying the composite exchange membrane obtained in step (2), wherein the freeze-drying conditions include: a time of 48 hours and a temperature of -20°C to obtain a PDDA / PSS / BC exchange membrane, recorded as (PDDA / PSS)2 / BC; the PDDA / PSS / BC exchange membrane includes a bacterial cellulose membrane and two layers of PDDA / PSS composite membrane supported on the bacterial cellulose membrane; the PDDA / PSS composite membrane includes a polydiallyldimethylammonium chloride membrane and a poly(sodium 4-styrenesulfonate) membrane supported on the polydiallyldimethylammonium chloride membrane.

[0060] Example 2

[0061] The method of Example 1 is followed, except that in step (2), the treated bacterial cellulose membrane obtained in step (1) is subjected to four PDDA / PSS composite membrane assembly treatments to obtain a PDDA / PSS / BC exchange membrane, designated as (PDDA / PSS)4 / BC; the PDDA / PSS / BC exchange membrane comprises a bacterial cellulose membrane and four layers of PDDA / PSS composite membranes loaded on the bacterial cellulose membrane; the PDDA / PSS composite membrane comprises a polydiallyldimethylammonium chloride membrane and a poly(sodium 4-styrenesulfonate) membrane loaded on the polydiallyldimethylammonium chloride membrane.

[0062] Example 3

[0063] The method of Example 1 is followed, except that in step (2), the treated bacterial cellulose membrane obtained in step (1) is subjected to 6 PDDA / PSS composite membrane assembly treatments to obtain a PDDA / PSS / BC exchange membrane, designated as (PDDA / PSS)6 / BC; the PDDA / PSS / BC exchange membrane comprises a bacterial cellulose membrane and 6 layers of PDDA / PSS composite membranes loaded on the bacterial cellulose membrane; the PDDA / PSS composite membrane comprises a polydiallyldimethylammonium chloride membrane and a poly(sodium 4-styrenesulfonate) membrane loaded on the polydiallyldimethylammonium chloride membrane.

[0064] Example 4

[0065] The method of Example 1 is followed, except that in step (2), the treated bacterial cellulose membrane obtained in step (1) is subjected to 8 PDDA / PSS composite membrane assembly treatments to obtain a PDDA / PSS / BC exchange membrane, recorded as (PDDA / PSS)8 / BC; the PDDA / PSS / BC exchange membrane includes a bacterial cellulose membrane and 8 layers of PDDA / PSS composite membranes supported on the bacterial cellulose membrane; the PDDA / PSS composite membrane includes a polydiallyldimethylammonium chloride membrane and a poly(sodium 4-styrenesulfonate) membrane supported on the polydiallyldimethylammonium chloride membrane.

[0066] Example 5

[0067] The method of Example 1 was followed, except that in step (2), the treated bacterial cellulose membrane obtained in step (1) was subjected to 10 PDDA / PSS composite membrane assembly processes to obtain a PDDA / PSS / BC exchange membrane, which was recorded as (PDDA / PSS) 10 / BC; the PDDA / PSS / BC exchange membrane includes a bacterial cellulose membrane and a 10-layer PDDA / PSS composite membrane loaded on the bacterial cellulose membrane; the PDDA / PSS composite membrane includes a polydiallyldimethylammonium chloride membrane and a poly(sodium 4-styrenesulfonate) membrane loaded on the polydiallyldimethylammonium chloride membrane.

[0068] Test Example 1

[0069] The BC obtained in step (1) of Example 1, the (PDDA / PSS)2 / BC obtained in step (3), the (PDDA / PSS)4 / BC in Example 2, the (PDDA / PSS)6 / BC in Example 3, the (PDDA / PSS)8 / BC in Example 4 and the (PDDA / PSS) in Example 5 were respectively 10 / BC was tested by FTIR, and the results were as follows Figure 1 As shown, according to Figure 1 It can be seen that at 2943.37cm-1 and 1473.62cm -1 The symmetrical stretching and bending vibration peaks of N-CH3 in PDDA are located at 1174 cm -1 The S=O stretching vibration peak of the sulfonic acid group in PSS gradually increases with the increase of the number of self-assembled layers, proving that this experimental method can control the preparation of PDDA / PSS / BC exchange membranes with the required number of self-assembled layers.

[0070] Test Example 2

[0071] The BC obtained in step (1) of Example 1, the (PDDA / PSS)2 / BC obtained in step (3), the (PDDA / PSS)4 / BC in Example 2, the (PDDA / PSS)6 / BC in Example 3, the (PDDA / PSS)8 / BC in Example 4 and the (PDDA / PSS) in Example 5 were respectively 10 / BC was tested by XRD, and the results were as follows Figure 2 As shown, according to Figure 2 It can be seen that the PDDA / PSS / BC exchange membrane after layer-by-layer self-assembly shows a new diffraction peak near 2θ 16°, proving the successful preparation of the self-assembled layer.

[0072] Test Example 3

[0073] The BC obtained in step (1) of Example 1, the (PDDA / PSS)2 / BC obtained in step (3), the (PDDA / PSS)4 / BC in Example 2, the (PDDA / PSS)6 / BC in Example 3, the (PDDA / PSS)8 / BC in Example 4 and the (PDDA / PSS) in Example 5 were respectively 10 The cross section of / BC was observed by scanning electron microscopy. Figures 3 to 8 As shown, Figure 3 This is the scanning electron microscope result of the cross section of BC. Figure 4 This is the scanning electron microscopy result of the cross section of (PDDA / PSS)2 / BC. Figure 5 This is the scanning electron microscopy result of the cross section of (PDDA / PSS)4 / BC. Figure 6 This is the scanning electron microscopy result of the cross section of (PDDA / PSS)6 / BC. Figure 7 This is the scanning electron microscopy result of the cross section of (PDDA / PSS)8 / BC. Figure 8 Yes (PDDA / PSS) 10 / BC cross-section scanning electron microscopy results, according to Figures 3 to 8 It can be seen that as the number of composite membrane assembly layers increases, the cross-sectional thickness of the film gradually increases.

[0074] Test Example 4

[0075] The BC obtained in step (1) of Example 1, the (PDDA / PSS)2 / BC obtained in step (3), the (PDDA / PSS)4 / BC in Example 2, the (PDDA / PSS)6 / BC in Example 3, the (PDDA / PSS)8 / BC in Example 4 and the (PDDA / PSS) in Example 5 were respectively 10 / BC was tested for tensile strength and conductivity. The tensile strength results are shown in Table 1 and Figure 9 The conductivity results are shown in Table 1 and Figure 10 As shown in Table 1 (Table 1 shows the conductivity results at 80°C), the tensile strength and conductivity test methods are as follows:

[0076] Tensile strength test: Use a cutter to cut the BC membrane and each PDDA / PSS / BC exchange membrane into three 4 cm × 1 cm × 0.4 cm (length × width × thickness) strips. Set the tensile speed to 1 mm / min and test using a universal tensile testing machine (AG-IC 5KN) according to GB / T1040.1-2006 to obtain the tensile fracture load (P) of the strips. Then, use the following formula:

[0077] T s =P / (b×d)

[0078] Calculate the tensile strength (T s ), where b is the initial width and d is the initial thickness;

[0079] Conductivity test: Using a CHI760E electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd., the BC membrane and each PDDA / PSS / BC exchange membrane were cut into 2cm×3cm sizes, placed in the electrochemical workstation, and the experimental parameters were adjusted to start the test.

[0080] In addition, the BC obtained in step (1) of Example 1, the (PDDA / PSS)2 / BC obtained in step (3), the (PDDA / PSS)4 / BC in Example 2, the (PDDA / PSS)6 / BC in Example 3, the (PDDA / PSS)8 / BC in Example 4 and the (PDDA / PSS) in Example 5 were respectively 10 / BC was used to test the hydrophilicity, and the contact angle results were as follows: Figures 11-16 As shown, the contact angle detection method is as follows:

[0081] The contact angle instrument used was JC2000C2E, manufactured by Shanghai Zhongchen Digital Technology Equipment Co., Ltd. The prepared dry, flat BC pure membrane and each PDDA / PSS / BC exchange membrane were cut into 8 cm × 2 cm membrane sheets and placed on the sample stage. Saturated water droplets were dripped onto the membrane surface using a microinjector. The contact angle was measured using the equipment software and the data was recorded. The specific data are shown in Table 1.

[0082] Table 1

[0083] serial number Tensile strength / MPa Conductivity / (mS / cm) Contact angle (°) BC 67.123 6±0.6 70.5 <![CDATA[(PDDA / PSS)2 / BC]]> 87.043 25±2 64.2 <![CDATA[(PDDA / PSS)4 / BC]]> 102.474 40±2.9 57.9 <![CDATA[(PDDA / PSS)6 / BC]]> 143.106 46±3 55.1 <![CDATA[(PDDA / PSS)8 / BC]]> 158.484 53±2.6 53.5 <![CDATA[(PDDA / PSS) 10 / BC]]> 159.844 85±3.6 48.1

[0084] It can be seen from the results in Table 1 that the mechanical strength and conductivity of the membrane gradually increase with the increase in the number of assembled layers. The PDDA / PSS / BC exchange membrane of the present invention has excellent conductivity, high tensile strength, and good hydrophilicity.

[0085] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0086] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A PDDA / PSS / BC exchange membrane, characterized in that: The PDDA / PSS / BC exchange membrane includes a bacterial cellulose membrane and a multilayer PDDA / PSS composite membrane loaded on the bacterial cellulose membrane; The PDDA / PSS composite membrane comprises a polydiallyldimethylammonium chloride membrane and a poly(sodium 4-styrenesulfonate) membrane supported on the polydiallyldimethylammonium chloride membrane.

2. The PDDA / PSS / BC exchange membrane according to claim 1, characterized in that: The PDDA / PSS / BC exchange membrane has a tensile strength of 80 to 160 MPa and an electrical conductivity of 20 to 100 mS / cm.

3. The PDDA / PSS / BC exchange membrane according to claim 1 or 2, characterized in that: The number of layers of the PDDA / PSS composite membrane is 2 to 16; The bacterial cellulose film contains hydroxyl groups.

4. A method for preparing the PDDA / PSS / BC exchange membrane according to any one of claims 1 to 3, characterized in that: The following steps are involved: The bacterial cellulose membrane is cleaned, then placed in an alkaline solution for purification, and then washed to obtain a treated bacterial cellulose membrane; The treated bacterial cellulose membrane was subjected to multiple assembling treatments of PDDA / PSS composite membrane to obtain a composite exchange membrane; The process of assembling the PDDA / PSS composite membrane comprises: placing the treated bacterial cellulose membrane in a polydiallyldimethylammonium chloride solution for polydiallyldimethylammonium chloride self-assembly, washing the membrane, placing the membrane in a poly(sodium 4-styrene sulfonate) solution for poly(sodium 4-styrene sulfonate) self-assembly, and then washing the membrane; The composite exchange membrane is freeze-dried to obtain a PDDA / PSS / BC exchange membrane.

5. The preparation method according to claim 4, characterized in that The operation of washing the bacterial cellulose membrane comprises: placing the bacterial cellulose membrane in water, and then stirring at 20 to 40° C. for 1 to 48 hours, wherein the stirring speed is 50 to 900 rpm; The concentration of the alkaline solution is 0.05 to 1 mol / L; The alkaline agent in the alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia; The purification operation includes: stirring at 20-100° C. for 1-48 hours, wherein the stirring speed is 50-900 rpm.

6. The preparation method according to claim 4 or 5, characterized in that The treated bacterial cellulose membrane was treated with 2 to 16 times to assemble the PDDA / PSS composite membrane.

7. The preparation method according to claim 4, characterized in that The concentration of the polydiallyldimethylammonium chloride solution is 0.01 to 3 mg / mL; The self-assembly process of the polydiallyldimethylammonium chloride comprises: stirring at 20-40° C. for 1-48 hours, wherein the stirring speed is 50-900 rpm.

8. The preparation method according to claim 4 or 7, characterized in that: The concentration of the poly (sodium 4-styrene sulfonate) solution is 0.01 to 3 mg / mL; The self-assembly operation of poly(sodium 4-styrene sulfonate) comprises: stirring at 20-40° C. for 1-48 hours, wherein the stirring speed is 50-900 rpm.

9. The preparation method according to claim 4, characterized in that The freeze-drying conditions include: a time of 4 to 72 hours and a temperature of -10 to -50°C.

10. Use of the PDDA / PSS / BC exchange membrane according to any one of claims 1 to 3 in a fuel cell membrane.

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