Conductive polymer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high-molecular polymers, and particularly relates to a conductive polymer and a preparation method and application thereof. The preparation method of the conductive polymer provided by the invention comprises the following steps: polyvinyl alcohol and a monomer containing a sulfonic acid group are subjected to a grafting reaction, and the grafting reaction comprises at least one of a free radical polymerization reaction, an atom transfer free radical polymerization reaction or a click chemical reaction. By adopting the grafting reaction defined in the invention, the monomer containing the sulfonic acid group can be grafted to the PVA molecular chain, ordered introduction of the sulfonic acid group is realized, the sulfonic acid group is uniformly distributed along the PVA molecular chain, and the problem of non-uniform distribution of the sulfonic acid group in a blending method is avoided; sulfonic acid groups which are uniformly introduced by a grafting method can construct a continuous ion transmission channel, so that the ion conductivity is improved.

Description

Technical Field

[0001] This application belongs to the technical field of polymer materials, and particularly relates to a conductive polymer, a preparation method thereof, and an application thereof. Background Art

[0002] Polyvinyl alcohol (PVA), as a common water-soluble polymer material, has excellent film-forming properties, strong mechanical properties, and good biodegradability, and is thus widely used in fields such as battery separators, sensors, and proton exchange membranes. However, the ionic conductivity of pure PVA films is poor, severely restricting its application in high-performance ionic conductive materials such as batteries and supercapacitors.

[0003] In the prior art, the modification of PVA mainly focuses on thermal properties, and the improvement effect on its ionic conductivity is limited, failing to effectively solve the application problem of PVA in high-performance ionic conductive materials. Summary of the Invention

[0004] One of the purposes of this application is to provide a preparation method of a conductive polymer to solve the problem that in the prior art, the modification of PVA mainly focuses on thermal properties, the improvement effect on its ionic conductivity is limited, and the application problem of PVA in high-performance ionic conductive materials cannot be effectively solved; the second purpose is to provide a conductive polymer; the third purpose is to provide a film material; the fourth purpose is to provide an application of the film material in the fields of sensors, proton exchange membranes, batteries, or supercapacitors.

[0005] To achieve the above purposes, the technical solutions adopted in this application are as follows:

[0006] According to one aspect of this application, a preparation method of a conductive polymer is provided, including the following steps:

[0007] Graft a monomer containing a sulfonic acid group onto polyvinyl alcohol, wherein the grafting reaction includes at least one of free radical polymerization reaction, atom transfer radical polymerization reaction, or click chemical reaction.

[0008] According to the above technical means, by using the grafting reaction defined in this application, the monomer containing a sulfonic acid group is grafted onto the PVA molecular chain, realizing the orderly introduction of sulfonic acid groups. The sulfonic acid groups are uniformly distributed along the PVA molecular chain, avoiding the problem of uneven distribution of sulfonic acid groups in the blending method. The sulfonic acid groups uniformly introduced by the grafting method can construct a continuous ion transport channel, thereby improving the ionic conductivity of the material. If the sulfonic acid groups are unevenly distributed in the PVA molecular chain after grafting, it will cause a change in the molecular chain conformation, forming a strong steric hindrance and resulting in difficult ion transport.

[0009] In some optional embodiments, the mass ratio of the polyvinyl alcohol to the monomer containing a sulfonic acid group is (1 - 2):(1.5 - 3).

[0010] In this application, by limiting the mass ratio of the polyvinyl alcohol to the monomer containing a sulfonic acid group, the ionic conductivity of the material can be further improved. If the mass ratio of the polyvinyl alcohol to the monomer containing a sulfonic acid group is too low, too few sulfonic acid groups are grafted, the lithium ion transport sites are reduced, resulting in difficult ion migration; if the mass ratio of the polyvinyl alcohol to the monomer containing a sulfonic acid group is too high, the molecular chain conformation changes, leading to an increase in steric hindrance and blocked ion transport, affecting the further improvement of the ionic conductivity.

[0011] In some optional embodiments, the weight-average molecular weight of the polyvinyl alcohol is 70,000 - 100,000; in this application, by limiting the weight-average molecular weight of the polyvinyl alcohol, the film-forming performance and grafting performance can be balanced. If the molecular weight of the polyvinyl alcohol is too low, it will be difficult to form a film, affecting subsequent applications; if the molecular weight of the polyvinyl alcohol is too high, it will be difficult to graft the sulfonic acid group, or even impossible to graft, which is not conducive to the improvement of the ionic conductivity.

[0012] In some optional embodiments, the monomer containing a sulfonic acid group includes at least one of sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium 4-vinylbenzenesulfonate, and vinylsulfonic acid.

[0013] According to another aspect of the present application, there is provided a conductive polymer prepared by the above preparation method.

[0014] According to the above technical means, by using the preparation method of the present application, a conductive polymer with uniformly distributed sulfonic acid groups along the PVA molecular chain can be obtained, which has a continuous ion transport channel and significantly improved ionic conductivity of the material.

[0015] In some optional embodiments, the conductive polymer includes a polyvinyl alcohol main chain and sulfonic acid groups grafted on the polyvinyl alcohol main chain, and the grafting rate of the sulfonic acid groups on the polyvinyl alcohol main chain is 50% - 80%.

[0016] In this application, by limiting the grafting rate of the sulfonic acid groups on the polyvinyl alcohol main chain, a higher ionic conductivity can be obtained. If the grafting rate is too high, the molecular chain conformation changes, leading to an increase in steric hindrance and blocked ion transport; if the grafting rate is too low, too few sulfonic acid groups are grafted, the lithium ion transport sites are reduced, resulting in difficult ion migration.

[0017] According to another aspect of the present application, there is provided a membrane material prepared by forming a film from the above conductive polymer through a film-forming technique.

[0018] According to the above technical means, since the film material is prepared by using the conductive polymer provided in the present application, the film material has high ionic conductivity. In addition, due to the uniform and ordered sulfonation modification of PVA, its molecular chains form an ordered conformation, having a good flexible structure, and can also improve the mechanical properties of the film material, enabling it to be applied in high-performance ionic conductive materials such as batteries, supercapacitors, and sensors.

[0019] In some alternative embodiments, the film-forming technique includes at least one of casting, electrospinning, or hot pressing.

[0020] In some alternative embodiments, the conductive polymer is mixed with a solvent to obtain a film-forming material, and the film material is prepared by a film-forming technique.

[0021] In some alternative embodiments, the film-forming material further includes at least one of an aldehyde crosslinking agent, an inorganic filler modified with a silane coupling agent, and a photoinitiator.

[0022] According to the above technical means, the addition of the aldehyde crosslinking agent can form an acetal structure through the aldehyde group and the hydroxyl group of PVA, reduce swelling, maintain structural stability, further improve the ionic conductivity, and improve the tensile strength of the material.

[0023] According to the above technical means, the addition of the inorganic filler modified with a silane coupling agent can improve the mechanical properties of the film material. The photoinitiator can generate free radicals. When used in combination with the inorganic filler modified with a silane coupling agent, it can promote the dehydration condensation reaction between the silane-modified layer on the surface of the inorganic filler and some sulfonic acid groups, thereby improving the ionic conductivity of the film material.

[0024] In some alternative embodiments, based on the mass of the solute in the film-forming material (i.e., the total mass of each component in the film-forming material except the solvent), the mass percentage content of the aldehyde crosslinking agent is 18%-30%. By limiting the dosage of the crosslinking agent in the present application, the degree of crosslinking can be controlled, thereby regulating the microporous structure and ion channel density of the material.

[0025] In some alternative embodiments, the mass percentage content of the inorganic filler modified with a silane coupling agent is 1%-10%. In the present application, by limiting the dosage of the inorganic filler modified with a silane coupling agent, the ionic conductivity and mechanical properties can be taken into account. If the inorganic filler is too little, the polymer crystallinity is relatively high and the ion transport is slow; if the inorganic filler is too much, it will block the ion transport channels, resulting in a decrease in ionic conductivity, and too much inorganic filler will also lead to a decrease in the mechanical properties of the polymer.

[0026] In some optional embodiments, based on the mass of the solute in the film-forming material, the mass percentage content of the photoinitiator is 0.5%-2%; in the present application, by limiting the amount of the photoinitiator, the further improvement of the ionic conductivity can be ensured. If the content of the initiator is too low, the dehydration condensation reaction between the silane modification layer on the surface of the inorganic filler and some sulfonic acid groups is insufficient, affecting the further improvement of the ionic conductivity and mechanical strength; if the initiator is in excess, too much initiator residue will be caused, resulting in a decrease in the ionic conductivity.

[0027] And / or, the aldehyde crosslinking agent includes at least one of glutaraldehyde, glyoxal, terephthalaldehyde;

[0028] And / or, the photoinitiator includes at least one of benzophenone, 2,4-dihydroxybenzophenone, acetophenone, etc.;

[0029] And / or, the inorganic filler includes at least one of silicon dioxide, titanium dioxide, aluminum oxide.

[0030] In some optional embodiments, after film formation, it further includes two hot pressing treatment steps. First, apply a pressure of 0.5-2 MPa at 60-80 °C for pre-pressing for 10-20 minutes to eliminate air bubbles, and then raise the temperature to 100-140 °C and apply a pressure of 10-30 MPa to hold for 10-50 minutes.

[0031] According to another aspect of the present application, there is provided an application of a film material in the fields of sensors, proton exchange membranes, batteries or supercapacitors, and the film material is the film material provided by the present application as described above.

[0032] Advantages of the present application:

[0033] (1) In the preparation method of the conductive polymer provided by the present application, the grafting reaction defined by the present application is used to graft the monomer containing sulfonic acid groups onto the PVA molecular chain, realizing the orderly introduction of sulfonic acid groups. The sulfonic acid groups are evenly distributed along the PVA molecular chain, avoiding the problem of uneven distribution of sulfonic acid groups in the blending method. The sulfonic acid groups uniformly introduced by the grafting method can construct a continuous ion transport channel, thereby improving the ionic conductivity of the material. If the sulfonic acid groups are unevenly distributed in the PVA molecular chain after grafting, it will cause the conformation of the molecular chain to change, forming a strong steric hindrance, resulting in difficult ion transport.

[0034] (2) The preparation method of the conductive polymer provided by this application can further improve the ionic conductivity of the material by limiting the mass ratio of polyvinyl alcohol to the monomer containing sulfonic acid groups. If the mass ratio of polyvinyl alcohol to the monomer containing sulfonic acid groups is too low, too few sulfonic acid groups are grafted, the lithium ion transport sites are reduced, resulting in difficult ion migration; if the mass ratio of polyvinyl alcohol to the monomer containing sulfonic acid groups is too high, the molecular chain conformation changes, resulting in increased steric hindrance, ion transport is blocked, and the further improvement of ionic conductivity is affected.

[0035] (3) The preparation method of the conductive polymer provided by this application can balance the film-forming performance and grafting performance by limiting the weight-average molecular weight of polyvinyl alcohol. If the molecular weight of polyvinyl alcohol is too low, it will cause difficulties in film formation and affect subsequent applications; if the molecular weight of polyvinyl alcohol is too high, it will lead to difficulties in grafting sulfonic acid groups, and even unable to graft, which is not conducive to the improvement of ionic conductivity.

[0036] (4) The conductive polymer provided by this application, using the preparation method of this application, can obtain a conductive polymer with sulfonic acid groups evenly distributed along the PVA molecular chain, having a continuous ion transport channel, and the ionic conductivity of the material is significantly improved.

[0037] (5) The conductive polymer provided by this application can obtain a high ionic conductivity by limiting the grafting rate of sulfonic acid groups on the main chain of polyvinyl alcohol. If the grafting rate is too high, the molecular chain conformation changes, resulting in increased steric hindrance and blocked ion transport; if the grafting rate is too low, too few sulfonic acid groups are grafted, the lithium ion transport sites are reduced, resulting in difficult ion migration.

[0038] (6) The film material provided by this application, due to using the above-mentioned conductive polymer provided by this application to prepare the film material, makes the film material have high ionic conductivity. In addition, due to the uniform and orderly sulfonation modification of PVA, its molecular chain forms an orderly conformation, having a good flexible structure, and can also improve the mechanical properties of the film material, enabling it to be applied in high-performance ionic conductive materials such as batteries, supercapacitors, and sensors.

[0039] (7) For the film material provided by this application, the addition of an aldehyde cross-linking agent can form an acetal structure through the aldehyde group and the hydroxyl group of PVA, reduce swelling, maintain structural stability, further improve ionic conductivity, and improve the tensile strength of the material.

[0040] (8) For the film material provided by this application, the addition of inorganic fillers modified with silane coupling agents can improve the mechanical properties of the film material. The photoinitiator can generate free radicals. When used in combination with inorganic fillers modified with silane coupling agents, it can promote the dehydration condensation reaction between the silane-modified layer on the surface of the inorganic filler and some sulfonic acid groups, thereby improving the ionic conductivity of the film material.

[0041] (9) The film material provided by this application further includes two hot pressing treatment steps after film formation. Among them, the pre-pressing treatment can soften the polymer chains and eliminate air bubbles (avoiding the decrease in ionic conductivity caused by pores in the film); the second hot pressing treatment can promote the orientation of molecular chains and enhance mechanical properties; the distribution of sulfonic acid groups (-SO3H) is optimized through hydrogen bonding and ionic cross-linking to improve the continuity of ion channels. The high-temperature and high-pressure treatment makes the sulfonic acid groups form a continuous phase separation structure, and the ion transport path is more regular; eliminating micropore defects can reduce stress concentration and increase the elongation at break.

[0042] (10) The application of the film material provided by this application in the fields of sensors, proton exchange membranes, batteries or supercapacitors, and the film material is the film material provided by the above-mentioned application of this application.

[0043] According to the above technical means, the application of the film material in the above fields has the same advantages as the above film material compared with the prior art, and will not be elaborated here. Detailed implementation manners

[0044] The following will illustrate the implementation manners of this application with reference to preferred embodiments. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be understood that the preferred embodiments are only for illustrating this application, rather than for limiting the protection scope of this application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0046] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0047] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include the end values and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] In the description of the embodiments of this application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone, these three situations.

[0049] In the description of the embodiments of this application, the term "at least one" refers to one or more than two (including two).

[0050] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), indicating that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0051] As described in the background art, in the prior art, the modification of PVA mainly focuses on thermal properties, and the improvement effect on its ionic conductivity is limited, and the application problem of PVA in high-performance ionic conductive materials cannot be effectively solved.

[0052] Therefore, this application provides a preparation method of a conductive polymer, including the following steps:

[0053] Carry out a grafting reaction on polyvinyl alcohol and a monomer containing a sulfonic acid group, wherein the grafting reaction includes at least one of a radical polymerization reaction, an atom transfer radical polymerization reaction, or a click chemical reaction.

[0054] According to the above technical means, a monomer containing a sulfonic acid group is grafted onto the PVA molecular chain using the grafting reaction defined in this application, achieving the orderly introduction of the sulfonic acid groups. The sulfonic acid groups are evenly distributed along the PVA molecular chain, avoiding the problem of uneven distribution of sulfonic acid groups in the blending method. The sulfonic acid groups uniformly introduced by the grafting method can form continuous ion transport channels, thereby improving the ionic conductivity of the material. If the sulfonic acid groups are unevenly distributed in the PVA molecular chain after grafting, it will cause the molecular chain conformation to change, forming a strong steric hindrance, making ion transport difficult.

[0055] In some optional embodiments, the mass ratio of the polyvinyl alcohol to the monomer containing a sulfonic acid group is (1-2):(1.5-3). As an example, the mass ratio of the polyvinyl alcohol to the monomer containing a sulfonic acid group can be 1:1.5, 1:2, 1:2.5, 1:3, 2:1.5, 2:2, 2:2.5, 2:3, or any range thereof.

[0056] In this application, the mass ratio of polyvinyl alcohol to the monomer containing sulfonic acid groups is limited. If the mass ratio of polyvinyl alcohol to the monomer containing sulfonic acid groups is too low, too few sulfonic acid groups are grafted, and the lithium ion transmission sites are reduced, causing difficulty in ion migration; if the mass ratio of polyvinyl alcohol to the monomer containing sulfonic acid groups is too high, the conformation of the molecular chain changes, resulting in increased steric hindrance and obstructed ion transmission.

[0057] In some optional embodiments, the weight average molecular weight of the polyvinyl alcohol is 70,000-100,000; as an example, the weight average molecular weight of the polyvinyl alcohol can be 70,000, 75,000, 80,000, 85,000, 90,000, 95,000, 100,000, or any range thereof. In the present application, by limiting the weight average molecular weight of the polyvinyl alcohol, it is possible to achieve a balance between film-forming performance and grafting performance. If the molecular weight of the polyvinyl alcohol is too low, film formation will be difficult, affecting subsequent applications; if the molecular weight of the polyvinyl alcohol is too high, it will make grafting of the sulfonic acid group difficult or even impossible, which is not conducive to improving ionic conductivity.

[0058] In some optional embodiments, the monomer containing a sulfonic acid group includes at least one of sodium p-styrene sulfonate, 2-acrylamide-2-methylpropane sulfonic acid, sodium 4-vinylbenzene sulfonate, and vinyl sulfonic acid.

[0059] It should be noted that the specific operations of free radical polymerization, atom transfer radical polymerization or click chemistry reaction are not particularly limited in this application, and can all be conventional operations in the field. For example:

[0060] In the present application, the free radical polymerization reaction may include the following steps:

[0061] (1) Dissolve polyvinyl alcohol in water until the solution is transparent and free of particles. To accelerate dissolution, dissolution can be carried out under stirring and heating conditions. The stirring speed can be 200 - 500 rpm, and the heating temperature can be 70 - 100 °C;

[0062] (2) Exclude oxygen (air) from the system, maintain a positive pressure environment, add monomers containing sulfonic acid groups and initiators (including but not limited to ammonium persulfate), and carry out a reaction while maintaining the pH of the system at 6 - 7 (adjust with 0.1 M NaOH solution if necessary);

[0063] In some alternative embodiments, the molar ratio of the monomer containing sulfonic acid groups to the initiator is (30 - 45):1, the reaction temperature is 70 - 100 °C, the reaction time is 4 - 8 hours, and the stirring speed during the reaction is 350 - 650 rpm;

[0064] (3) Cool the reaction system, add ethanol, let it stand, separate the precipitate, carry out acidification treatment, separate the product, and dry it to obtain a conductive polymer, denoted as PVA - g - SO3H;

[0065] In some alternative embodiments, cool the reaction system to room temperature, let it stand for 10 - 20 hours, and the volume ratio of the added ethanol to the volume of the reaction system materials is (1 - 3):(2 - 6);

[0066] In some alternative embodiments, the acidification treatment includes: immersing the precipitate in a 0.5 - 1.5 M HCl solution and magnetically stirring for 10 - 24 hours (200 - 400 rpm); the drying operation includes: drying at 50 - 80 °C for 12 - 24 h to constant weight.

[0067] In this application, the atom transfer radical polymerization and click chemical reaction may include the following steps:

[0068] (1) Carry out an esterification reaction between polyvinyl alcohol and an excessive amount of acylating agent to introduce an initiation site on the polyvinyl alcohol molecular chain to obtain a macro - initiator;

[0069] In some alternative embodiments, the esterification reaction temperature is 0 - 5 °C, and the reaction time is 12 - 24 hours; the reaction product is precipitated with cold diethyl ether (it can be precipitated three times) and vacuum - dried to obtain a white flocculent macro - initiator;

[0070] In some alternative embodiments, the acylating agent includes but is not limited to at least one of 2 - bromoisobutyryl bromide (BIBB), propionyl chloride, 2 - chlorobutyryl chloride, etc.;

[0071] (2) Construct a PMDETA catalytic system. Dissolve the copper catalyst and the PMDETA ligand in an organic solvent according to a molar ratio of (1 - 3):(1.2 - 3.6) (for example, it can be N,N - dimethylformamide (DMF)). Under a protective atmosphere, add the macro - initiator obtained in the above step and the monomer containing a sulfonic acid group (the mass ratio of PVA to the monomer containing a sulfonic acid group is (1 - 2):(1.5 - 3)). Stir and react at 60 - 80 °C for 12 - 24 hours, quickly inject liquid nitrogen to quench the reaction, remove the copper catalyst through a neutral alumina column, and place it at 60 - 80 °C for 12 - 24 h to remove the solvent to obtain the conductive polymer.

[0072] In some alternative embodiments, the PMDETA ligand includes, but is not limited to, at least one of pentamethyldiethylenetriamine, tetramethylethylenediamine, 2,2'-bipyridine, triethylenediamine, 2,4,6 - trimethylaniline; and / or, the copper catalyst includes, but is not limited to, at least one of cuprous iodide, cuprous chloride, cuprous bromide, cuprous acetate.

[0073] In some alternative embodiments, the molar ratio of PVA to the copper catalyst is (1 - 1.5):(1.1 - 2.3).

[0074] In this application, a PMDETA catalytic system is constructed. Among them, the PMDETA ligand can form a stable complex with the copper catalyst, reduce the oxidation potential, and extend the catalyst life (avoiding the oxidation of Cu+→Cu2+); regulate the reaction kinetics, improve the grafting efficiency of the monomer containing a sulfonic acid group, and thus further improve the ionic conductivity.

[0075] According to another aspect of the present application, a conductive polymer is provided, which is prepared by the above - mentioned preparation method.

[0076] According to the above technical means, by using the preparation method of the present application, a conductive polymer with sulfonic acid groups uniformly distributed along the PVA molecular chain can be obtained, which has a continuous ion transport channel, and the ionic conductivity of the material is significantly improved.

[0077] In some alternative embodiments, the conductive polymer includes a polyvinyl alcohol main chain and sulfonic acid groups grafted on the polyvinyl alcohol main chain, and the grafting rate of the sulfonic acid groups on the polyvinyl alcohol main chain is 50% - 80%. As an example, the grafting rate of the sulfonic acid groups on the polyvinyl alcohol main chain can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, or within the range composed of any of the above values.

[0078] In this application, by limiting the grafting rate of sulfonic acid groups on the main chain of polyvinyl alcohol, a high ionic conductivity can be obtained. If the grafting rate is too high, the molecular chain conformation changes, resulting in an increase in steric hindrance and hindering ion transport; if the grafting rate is too low, too few sulfonic acid groups are grafted, reducing the lithium ion transport sites and making ion migration difficult.

[0079] According to another aspect of the present application, a membrane material is provided, which is prepared from the above conductive polymer by a film-forming technique.

[0080] According to the above technical means, since the membrane material is prepared from the above conductive polymer provided by the present application, the membrane material has a high ionic conductivity. In addition, due to the uniform and orderly sulfonation modification of PVA, its molecular chain forms an orderly conformation and has a good flexible structure, which can also improve the mechanical properties of the membrane material, enabling it to be applied in high-performance ionic conductive materials such as batteries, supercapacitors, and sensors.

[0081] In some alternative embodiments, the film-forming technique includes at least one of a casting method, an electrospinning method, or a hot pressing method.

[0082] In some alternative embodiments, the conductive polymer is mixed with a solvent to obtain a film-forming material, and the membrane material is prepared by a film-forming technique.

[0083] In some alternative embodiments, the film-forming material further includes at least one of an aldehyde crosslinking agent, an inorganic filler modified with a silane coupling agent, and a photoinitiator.

[0084] According to the above technical means, the addition of an aldehyde crosslinking agent can form an acetal structure through the aldehyde group and the hydroxyl group of PVA, reduce swelling, maintain structural stability, further improve the ionic conductivity, and improve the tensile strength of the material.

[0085] According to the above technical means, the addition of an inorganic filler modified with a silane coupling agent can improve the mechanical properties of the membrane material, and the photoinitiator can generate free radicals. When used in combination with the inorganic filler modified with a silane coupling agent, it can promote the dehydration condensation reaction between the silane modification layer on the surface of the inorganic filler and some sulfonic acid groups, thereby improving the ionic conductivity of the membrane material.

[0086] In some alternative embodiments, based on the mass of the solute in the film-forming material (i.e., the total mass of all components in the film-forming material except the solvent), the mass percentage content of the aldehyde crosslinking agent is 18% - 30%; as an example, the mass percentage content of the aldehyde crosslinking agent can be 18%, 20%, 23%, 25%, 28%, 30%, or within any range composed of the above values. By limiting the amount of the crosslinking agent in this application, the degree of crosslinking can be controlled, thereby regulating the microporous structure and ion channel density of the material.

[0087] In some optional embodiments, the weight percentage of the silane coupling agent-modified inorganic filler is 1%-10%; as an example, the weight percentage of the silane coupling agent-modified inorganic filler can be 1%, 3%, 5%, 7%, 9%, 10%, or any range thereof. In this application, by limiting the amount of the silane coupling agent-modified inorganic filler, it is possible to achieve a balance between ionic conductivity and mechanical properties. If the inorganic filler is too little, the polymer crystallinity is relatively high, and ion transport is slow; if the inorganic filler is too much, it will block the ion transport channel, resulting in a decrease in ionic conductivity. Excessive inorganic filler can also lead to a decrease in the mechanical properties of the polymer.

[0088] In some optional embodiments, the mass percentage of the photoinitiator is 0.5%-2% based on the mass of the solute in the film-forming material; as an example, the mass percentage of the photoinitiator can be 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.7%, 2%, or within the range of any of the above values. In the present application, by limiting the amount of photoinitiator, it is possible to ensure further improvement of ionic conductivity. If the initiator content is too low, the dehydration condensation reaction between the silane modified layer on the surface of the inorganic filler and part of the sulfonic acid group is not sufficient, affecting the further improvement of ionic conductivity and mechanical strength; if the initiator is excessive, it will cause excessive initiator residue, resulting in a decrease in ionic conductivity.

[0089] and / or, the aldehyde cross-linking agent comprises at least one of glutaraldehyde, glyoxal, and terephthalaldehyde;

[0090] And / or, the photoinitiator includes at least one of benzophenone, 2,4-dihydroxybenzophenone, acetobenzoate, etc.;

[0091] And / or, the inorganic filler includes at least one of silicon dioxide, titanium dioxide, and aluminum oxide.

[0092] It should be noted that, in the present application, the inorganic filler modified with the silane coupling agent can be obtained through commercial channels or can be made in the laboratory, and this application does not make any specific restrictions.

[0093] In some optional embodiments, the process of casting into a film further includes a step of surface tension treatment (silanization treatment) of the glass plate. The specific treatment methods and steps are conventional in the art and are not specifically limited in this application. In this application, the surface tension treatment of the glass plate has the following beneficial effects: (1) Reducing surface energy: The silane reagent contains a hydrophobic group (long-chain alkyl), and a hydrophobic layer is formed on the glass surface through chemical bonding, reducing the surface energy and preventing the hydrophilic polymer solution from overly wetting or penetrating the substrate. (2) Improving demoulding property: The silane layer forms a physical / chemical barrier on the glass surface, reducing the van der Waals force and hydrogen bond interaction between the film material and the substrate, and avoiding the film from adhering to the glass due to shrinkage stress during the drying process; (3) Controlling film formation uniformity: The surface hydrophobicity regulates the spreading behavior of the solution, ensuring uniform film thickness and reducing edge curling or thickness gradient.

[0094] In some optional embodiments, after film formation, it further includes two-stage hot pressing treatment steps. First, apply a pressure of 0.5 - 2 MPa at 60 - 80 °C for pre-pressing for 10 - 20 minutes to eliminate air bubbles, and then raise the temperature to 100 - 140 °C and apply a pressure of 10 - 30 MPa and hold for 10 - 50 minutes. As an example, the temperature of the pre-pressing can be 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, or within the range composed of any of the above values; the pressure of the pre-pressing can be 0.5 MPa, 0.8 MPa, 1 MPa, 1.3 MPa, 1.5 MPa, 1.7 MPa, 2 MPa, or within the range composed of any of the above values; the time of the pre-pressing can be 10 minutes, 12 minutes, 15 minutes, 16 minutes, 18 minutes, 20 minutes, or within the range composed of any of the above values; as an example, the temperature of the second-stage hot pressing can be 100 °C, 105 °C, 110 °C, 125 °C, 130 °C, 140 °C, or within the range composed of any of the above values; the pressure of the second-stage hot pressing can be 10 MPa, 13 MPa, 15 MPa, 18 MPa, 20 MPa, 25 MPa, 30 MPa, or within the range composed of any of the above values; the time of the second-stage hot pressing can be 10 minutes, 15 minutes, 25 minutes, 30 minutes, 45 minutes, 50 minutes, or within the range composed of any of the above values.

[0095] In this application, the effects of the two-stage hot pressing are as follows:

[0096] Pre-pressing: Soften the polymer chains and eliminate air bubbles (avoiding a decrease in ionic conductivity caused by pores in the film);

[0097] Second hot pressing: Promote the orientation of molecular chains and enhance mechanical properties; optimize the distribution of sulfonic acid groups (-SO3H) through hydrogen bonding and ionic cross-linking, improve the continuity of ion channels, and form a continuous phase separation structure of sulfonic acid groups through high-temperature and high-pressure treatment, making the ion transport path more regular; eliminating micropore defects can reduce stress concentration and increase the elongation at break.

[0098] In some alternative embodiments, for the solution with a photoinitiator added, it further includes a step of ultraviolet irradiation cross-linking, and the specific operating parameters are conventional in the art and are not specifically limited in this application.

[0099] It should be noted that the film formation methods such as the casting method, electrospinning method, and hot pressing method in this application can all be conventional operations in the art. In order to improve the performance of the film material, this application can appropriately improve the operation methods of the film formation technology.

[0100] In some alternative embodiments, in order to improve the fiber formability, when preparing the film material by the electrospinning method, some spinning aids can be added, and the addition amount of the spinning aids accounts for 0.5%-8% of the total mass of the spinning solution; the spinning aids include but are not limited to at least one of polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and polycarbonate. The specific operating parameters of electrospinning are conventional in the art and are not specifically limited in this application.

[0101] In some alternative embodiments, in order to obtain a flexible film, it further includes a step of treating the film material with phosphoric acid. The concentration of phosphoric acid can be 30wt%-80wt%.

[0102] According to another aspect of the present application, there is provided an application of the film material in the fields of sensors, proton exchange membranes, batteries, or supercapacitors, and the film material is the film material provided in the present application above.

[0103] According to the above technical means, the application of the film material in the above fields has the same advantages as the above film material compared with the prior art, and will not be elaborated here.

[0104] Next, with reference to specific embodiments, the present application will be described. It should be noted that these embodiments are only descriptive and do not limit the present application in any way.

[0105] For those where specific experimental steps or conditions are not indicated in the examples, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0106] Example 1

[0107] This example provides a preparation method for a conductive polymer and a film material, and the specific operation steps and parameters are as follows:

[0108] Raw materials: Polyvinyl alcohol (PVA, weight-average molecular weight 85000), sodium p-styrenesulfonate (SSS), ammonium persulfate (APS);

[0109] Equipment: Four-necked flask (500 mL) + Condensation reflux device, equipped with mechanical stirring (rotation speed 0 - 1000 rpm);

[0110] Detailed steps:

[0111] (1) Accurately weigh 5.00 ± 0.01 g of PVA, add 100 mL of ultrapure water, heat in a water bath at 90 ± 1 °C, with a mechanical stirring speed of 300 rpm, and continue for 2 hours until the solution is transparent and free of particles;

[0112] (2) Pass nitrogen for 30 minutes to remove oxygen, maintain a positive pressure environment, and sequentially add 8.00 g of SSS and 0.250 g of APS (molar ratio SSS:APS = 35:1); Heat in an oil bath at 80 ± 0.5 °C for 6 hours, with a stirring speed of 500 rpm; Take samples every 1 hour to detect the pH value (maintain pH 6 - 7, and add 0.1 M NaOH dropwise for adjustment if necessary);

[0113] (3) After cooling the reaction solution to 25 °C, pour it into 200 mL of ethanol (volume ratio 1:2), let it stand for 12 hours, and separate the precipitate. Acidification treatment: Immerse the precipitate in 1 M HCl solution (500 mL), and stir magnetically for 24 hours (200 rpm). Dry in a vacuum oven at 60 °C for 24 h until constant weight to obtain the conductive polymer, denoted as PVA-g-SO3H;

[0114] (4) Dissolve PVA-g-SO3H in water to obtain a 5 wt% PVA-g-SO3H aqueous solution, add 1.8 g of glutaraldehyde (the mass percentage of glutaraldehyde is 26% based on the total mass of glutaraldehyde and PVA-g-SO3H) to the above aqueous solution, perform surface tension treatment (silanization treatment) on the glass plate, cast a film on the surface of the treated glass plate, and dry in vacuum at 60 °C for 12 hours, controlling the film thickness to 100 μm;

[0115] Among them, the step of performing surface tension treatment on the glass plate is conventional in the field. The specific treatment steps in this embodiment are as follows:

[0116] S1, Immerse the glass plate in a piranha solution (piranha solution, 80 wt% concentrated H2SO4:30 wt% H2O2 = 3:1, volume ratio) and perform ultrasonic treatment for 30 minutes to remove organic pollutants; Rinse 3 times with ultrapure water and dry with nitrogen;

[0117] S2, Place the washed glass plate in an oxygen plasma treatment instrument (power 100 W, oxygen flow rate 50 sccm) and treat for 5 minutes to generate high-density surface hydroxyl groups;

[0118] S3, Prepare a toluene solution of 1-2% silane reagent (preferably long-chain alkyl silane such as octadecyltrichlorosilane (OTS) or fluorosilane such as FOTS). In this example, it is a toluene solution of OTS with a mass concentration of 15%. Immerse the glass plate in the solution under nitrogen protection and let it stand at 25°C for 2 hours to form a self-assembled monolayer (SAMs).

[0119] S4, Take out the glass plate and ultrasonically clean it with toluene and ethanol for 5 minutes each to remove physically adsorbed silane molecules. Then heat-treat it in a vacuum oven at 120°C for 1 hour to promote the formation of Si-O-Si covalent bonds. The relative humidity during the treatment process should be <40% (too high will cause silane hydrolysis and polymerization, forming an uneven coating).

[0120] Example 2

[0121] This example provides a preparation method for a conductive polymer and a film material. The specific operation steps and parameters are as follows:

[0122] (1) In a dry reactor under nitrogen protection, react 10 g of PVA with an excess of 2-bromoisobutyryl bromide (BIBB) in DMF solvent at 0-5°C for 24 hours to introduce an initiation site onto the PVA chain through an esterification reaction. The reaction product is precipitated three times with cold diethyl ether and dried in vacuum to obtain a white flocculent macromolecular initiator.

[0123] (2) Construct a PMDETA catalytic system. Copper catalyst cuprous iodide and pentamethyldiethylenetriamine ligand are dissolved in organic solvent DMF in a molar ratio of 1:1.2. Add the macromolecular initiator obtained in the above step and a monomer containing a sulfonic acid group (the mass ratio of PVA to the monomer containing a sulfonic acid group is 1:1.5), and continuously stir and react in a constant-temperature oil bath at 60°C for 12 hours. After the reaction, quickly inject liquid nitrogen to quench the reaction, and remove the copper catalyst through a neutral alumina column to obtain the product conductive polymer.

[0124] (3) Dissolve the product in deionized water to prepare an aqueous solution with a concentration of 5 wt%. Cast it into a film in a polytetrafluoroethylene template, and then perform two-stage hot pressing treatment. First, apply a pressure of 1 MPa at 80°C for 10 minutes to remove bubbles, and then raise the temperature to 120°C and apply a pressure of 10 MPa for 30 minutes. The thickness of the obtained film material is 100 μm.

[0125] Example 3

[0126] This example provides a preparation method for a conductive polymer and a film material. The specific operation steps and parameters are as follows:

[0127] (1) Add 5% by mass of nano-SiO2 modified with silane coupling agent (average particle size 20 nm, commercially available product) and 0.5% benzophenone to the PVA-g-SO3H solution prepared in Example 2, and treat it with a high-shear emulsifier (12,000 rpm) for 30 minutes to form a homogeneous dispersion. Control the blade gap to 100 μm on a polished glass substrate and dry it at room temperature for 24 hours to form a primary film;

[0128] (2) Carry out ultraviolet irradiation cross-linking using a medium-pressure mercury lamp light source (wavelength 365 nm, intensity 50 mW / cm 2 , time 10 minutes), and the cumulative irradiation dose is 3000 mJ / cm 2 .

[0129] Example 4

[0130] This example provides a preparation method of a conductive polymer and a film material, and the specific operation steps and parameters are as follows:

[0131] (1) Prepare a 10 wt% DMSO solution of the PVA-g-SO3H obtained in Example 1, and introduce 0.5% polyethylene oxide (PEO, weight-average molecular weight 600,000) as a spinning aid to improve the fiber formability;

[0132] (2) Electrospinning parameters: voltage 20 kV, receiving distance 15 cm, flow rate 1 mL / h;

[0133] (3) Immerse it in 30%, 50%, and 70% by mass phosphoric acid aqueous solutions for 2 hours in sequence, and finally treat it in 80 wt% concentrated phosphoric acid for 12 hours to obtain a flexible self-supporting film, and control the film thickness to 50 μm.

[0134] Example 5

[0135] This example provides a preparation method of a conductive polymer and a film material. The difference from Example 1 is that glutaraldehyde is not added in step (4).

[0136] Example 6

[0137] This example provides a preparation method of a conductive polymer and a film material. The difference from Example 1 is that in step (4), 5% of nano-SiO2 modified with silane coupling agent (average particle size 20 nm) is added based on the total mass of the film-forming solution.

[0138] Example 7

[0139] This example provides a preparation method of a conductive polymer and a film material. The difference from Example 2 is that in step (3), two-stage hot pressing treatment is not included.

[0140] Example 8

[0141] This embodiment provides a preparation method of a conductive polymer and a film material. The difference compared with Embodiment 3 is that in step (2), the photoinitiator benzophenone is not added.

[0142] Example 9

[0143] This embodiment provides a preparation method of a conductive polymer and a film material. The difference compared with Embodiment 1 is that in step (1), the weight-average molecular weight of PVA is 95000, and the mass ratio of PVA to sodium p-vinylbenzenesulfonate is 1:2.

[0144] Comparative Example 1

[0145] This comparative example provides a preparation method of a conductive polymer and a film material. The difference compared with Embodiment 1 is that PVA (weight-average molecular weight of 85000) and polystyrenesulfonic acid (weight-average molecular weight of 70000) are blended at a mass ratio of 1:1.

[0146] Comparative Example 2

[0147] This comparative example provides a preparation method of a film material. The specific steps and operating parameters are as follows:

[0148] (1) Immerse PVA powder in 98% concentrated sulfuric acid and react at 60°C for 2 hours;

[0149] (2) Dissolve the sulfonated PVA in water to obtain an aqueous solution with a mass concentration of 5%. Cast a film according to the method of Embodiment 5 and vacuum dry it at 60°C for 12 hours. Control the film thickness to be 100 μm.

[0150] Comparative Example 3

[0151] This comparative example provides a preparation method of a film material. The specific steps and operating parameters are as follows:

[0152] (1) Mix polyvinyl alcohol and sodium p-styrenesulfonate at a mass ratio of 1:1.6 and dissolve them in water to obtain an aqueous solution with a mass concentration of 5%;

[0153] (2) Cast a film according to the method of Embodiment 5 and vacuum dry it at 60°C for 12 hours. Control the film thickness to be 100 μm.

[0154] Test Example

[0155] It should be noted that known methods and equipment in the field can be used to test the performance of the obtained film material. The specific test method in this application is as follows:

[0156] Grafting rate: Accurately weigh a certain amount of conductive polymer, dissolve it in dimethyl sulfoxide, and then titrate it with a 0.1 moL / L sodium hydroxide standard solution. Calculate the content of sulfonic acid groups based on the amount of sodium hydroxide consumed, and then obtain the grafting rate.

[0157] Ionic conductivity: The membrane materials prepared in the example and comparative example groups were assembled into stainless steel symmetric cells for electrochemical impedance testing. An electrochemical workstation was used to perform electrochemical impedance testing on the cells at room temperature. The test frequency range was 1 Hz to 1 MHz, the perturbation amplitude was 10 mV. After the cells were left standing at room temperature for 12 h before the test, the AC impedance of the cells was measured, and then the ionic conductivity was calculated.

[0158] Tensile strength: The test was carried out based on the national standard GB / T 1040.1-2018. A gradually increasing tensile load was applied in the length direction of the standard specimen of the membrane material to cause it to deform until failure. The maximum tensile stress required when the specimen failed was the tensile strength.

[0159] Test method for elongation at break: The test was carried out based on the national standard GB / T 1040.1-2018. A gradually increasing tensile load was applied in the length direction of the standard specimen of the membrane material to cause it to deform until failure. The ratio of the maximum tensile length required when the specimen failed to the original specimen length was processed to obtain the elongation at break.

[0160] The test results of each example and comparative example are shown in the following table:

[0161] Table 1

[0162]

[0163] From the above data comparison, it can be seen that using the conductive polymer provided in the examples of the present application to prepare the membrane material significantly improves the ionic conductivity of the membrane material compared with the blending method (Comparative Example 1 and Comparative Example 3) and the direct sulfonation method (Comparative Example 2). By comparing the data between the examples, it can be seen that through the regulation of the film-forming technology (the use of inorganic fillers, aldehyde cross-linking agents, photoinitiators, two-stage hot pressing, etc.), further regulation of the ionic conductivity and mechanical properties of the membrane material can be achieved.

[0164] Obviously, the above examples are only illustrations clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a conductive polymer, characterized in that, It includes the following steps: Perform a grafting reaction on polyvinyl alcohol and a monomer containing a sulfonic acid group, wherein the grafting reaction includes at least one of free radical polymerization, atom transfer radical polymerization, or click chemical reaction.

2. The preparation method of the conductive polymer according to claim 1, characterized in that, The mass ratio of the polyvinyl alcohol to the monomer containing a sulfonic acid group is (1 - 2):(1.5 - 3).

3. The preparation method of the conductive polymer according to claim 1, wherein The weight average molecular weight of the polyvinyl alcohol is 70,000 - 100,000; And / or, the monomer containing a sulfonic acid group includes at least one of sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium 4-vinylbenzenesulfonate, and vinylsulfonic acid.

4. A conductive polymer, characterized in that, It is prepared by the preparation method according to any one of claims 1 - 3.

5. The conductive polymer according to claim 4, characterized in that, It includes a polyvinyl alcohol main chain and sulfonic acid groups grafted on the polyvinyl alcohol main chain, and the grafting rate of the sulfonic acid groups on the polyvinyl alcohol main chain is 50% - 80%.

6. A film material, characterized in that, It is prepared by a film-forming technique from the conductive polymer according to claim 4 or 5.

7. The film material according to claim 6, wherein Mix the conductive polymer with a solvent to obtain a film-forming material, and prepare a film material by a film-forming technique; And / or, the film-forming technique includes at least one of a casting method, an electrospinning method, or a hot pressing method.

8. The film material according to claim 7, characterized in that, In the film-forming material, it further includes at least one of an aldehyde crosslinking agent, a photoinitiator, and an inorganic filler modified with a silane coupling agent.

9. The film material according to claim 8, wherein Based on the mass of the solute in the film-forming material, the mass percentage content of the aldehyde crosslinking agent is 18% - 30%; And / or, based on the mass of the solute in the film-forming material, the mass percentage content of the photoinitiator is 0.5% - 2%; And / or, based on the mass of the solute in the film-forming material, the mass percentage content of the inorganic filler modified with a silane coupling agent is 1% - 10%; And / or, the aldehyde crosslinking agent includes at least one of glutaraldehyde, glyoxal, and terephthalaldehyde; And / or, the photoinitiator includes at least one of benzophenone, 2,4-dihydroxybenzophenone, and acetophenone; And / or, the inorganic filler includes at least one of silicon dioxide, titanium dioxide, and aluminum oxide.

10. The film material according to any one of claims 7-9, characterized in that, After film formation, it further includes two hot pressing treatment steps, specifically including: applying a pressure of 0.5 - 2 MPa at 60 - 80 °C for pre-pressing for 10 - 20 minutes; then raising the temperature to 100 - 140 °C and applying a pressure of 10 - 30 MPa and maintaining for 10 - 50 minutes.

11. An application of a membrane material in the fields of sensors, proton exchange membranes, batteries or supercapacitors, characterized in that, The film material is the film material according to any one of claims 6 - 10.

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