RU2481885C1 - Method of producing composite membrane with fixed polyaniline layer thickness - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to articles made from high-molecular weight polymer compounds. Disclosed is a method of producing a composite membrane with a fixed polyaniline layer thickness, which involves boiling the starting non-conducting film of a copolymer of tetrafluoroethylene and perfluoro(3,6-dioxa-4-methyl-7-octene)sulphonyl fluoride (F-4SF) in 10% NaOH solution for 10-40 minutes to form a charged sulphonated layer of MF-4SK with a different thickness, washing the obtained film with distilled water, conversion thereof to H⁺ form, subsequent synthesis of polyaniline with a charged sulphonated layer through successive action of 1 M solution of protonated aniline (C₆H₅NH⁺ ₃) for 1 hour and 0.1 M ammonium persulphate (NH₄)₂S₂O₈ polymerisation initiator for 1 hour and boiling in ammonia water for soft alkaline saponification of the remaining inert non-conducting F-4CF film.

EFFECT: method of producing a composite membrane with a controlled thickness of polyaniline layer, having high electroconductivity and selectivity.

1 cl, 1 tbl, 6 dwg

Description

The invention relates to products from high molecular weight polymer compounds. It can be used in electrochemical devices for water purification, electrodialysis concentration of salt solutions and separation of multicomponent mixtures, membrane chlor-alkali electrolysis, in hydrogen-oxygen or methanol fuel cells, as well as in sensor devices.

A known method of forming films based on polyaniline, namely, that the film is applied by centrifugation from a solution additionally containing polyvinyl alcohol in the following ratio by weight of components: polyaniline: formic acid: polyvinyl alcohol 1: 40: 0.2-1: 40: 1 , 7, and heat treatment is carried out at a temperature of 80-120 ° C (patent No. 1805790, IPC (6) H01L 21/312). The disadvantage of this method is its energy intensity (the use of a centrifuge and oven).

A known method for producing a composite ion-exchange membrane modified with nanoparticles of a dopant gradient-distributed over the membrane thickness, using finely dispersed hydrated zirconium phosphate Zr (HPO ₄ ) ₂ H ₂ O, or finely divided hydrated zirconium oxide ZrO ₂ H ₂ O, or finely dispersed hydrated silicon oxide SiO ₂ · H ₂ O, polyaniline or particulate, wherein the gradient distribution of the inorganic dopant is obtained by synthesis it directly in the polymeric matrix in otorrhea administered one of the components of the synthesized dopant, and the second component is treated with one of the surfaces of the polymer matrix (RF patent №2352384, IPC B01D 71/00 (2006.01), B82B 1/00 (2006.01)). The method includes casting at least one additional matrix layer on top of the first layer, with each subsequent additional layer containing a relatively larger amount of dopant. However, the disadvantage of this method is the multi-stage and complexity of the synthesis, while the resulting membrane has a gradient distribution of the modifying component.

A known method of producing a composite ion-exchange membrane using pre-preparation of the base sulfocationite membrane Nafion by successively boiling for 1 hour in solutions of hydrogen peroxide, water and sulfuric acid. After that, the Nafion membrane is washed with water and balanced with a solution of sulfuric acid (from 15 minutes to 72 hours), and then the aniline is polymerized in the Nafion membrane matrix by sorption from a solution of protonated aniline followed by its polymerization in the presence of ammonium persulfate, after which the composite is boiled in water, sulfuric acid and again in water (US patent No. 6465120, H01M 8/10, 2002). The disadvantage of the method of obtaining such membranes is the multi-stage synthesis and the use of high concentrations of polymerizing solutions.

A known method for producing a composite ion-exchange membrane containing a perfluorinated sulfocationite ion exchange matrix and a polyaniline layer on the surface of the membrane, made in the form of a barrier layer containing inclusions of polyaniline particles with a diameter of 0.3-2.3 μm, the barrier layer being formed by diffusion through perfluorinated sulfocationite ion exchange the membrane, first, a protonated aniline solution, and then an aqueous solution of ammonium persulfate as a polymerization initiator with an autocom aliticheskoy polymerization protonated aniline (RF patent №2411070, B01D 71/60 (2006/01)). The membranes have a gradient distribution of the polyaniline layer, which leads to a strong decrease in the electrical conductivity of the composite membrane.

в течение 1 часа и инициатора полимеризации 0,1 M персульфата аммония (NH₄)₂S₂O₈ в течение 1 часа (S.Tan, D.Belanger Characterization and transport properties of Nafion/polyaniline composite membranes // J. Phys. Chem. 2005. V.109. P.23480-23490). Способ получения неконтролируемый, поэтому получаемые мембраны имеют градиентное распределение слоя полианилина, который приводит к сильному снижению удельной электропроводности композиционной мембраны.The closest analogue to the claimed method is a method for producing a composite ion-exchange membrane, consisting of a perfluorinated sulfocationite ion exchange membrane (Nafion) and a polyaniline layer formed by successive exposure to a 1 M solution of protonated aniline

for 1 hour and a polymerization initiator of 0.1 M ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ for 1 hour (S. Tan, D. Belanger Characterization and transport properties of Nafion / polyaniline composite membranes // J. Phys. Chem. 2005. V.109. P.23480-23490). The production method is uncontrolled, so the resulting membranes have a gradient distribution of the polyaniline layer, which leads to a strong decrease in the electrical conductivity of the composite membrane.

The technical result of the claimed invention is the development of a controlled method for producing a composite membrane with a fixed thickness of the polyaniline layer, which has high electrical conductivity and selectivity.

The technical result is achieved by the fact that the initial non-conductive film of a copolymer of tetrafluoroethylene and perfluoro (3,6-dioxa-4-methyl-7-octene) sulfonyl fluoride (F-4CF) is subjected to boiling for alkaline saponification of sulfonyl fluoride groups with a solution of 10% NaOH for 10-40 min, in accordance with the scheme:

в течение 1 часа и 0,1 M инициатора полимеризации персульфата аммония (NH₄)₂S₂O₈ в течение 1 часа, а затем кипятят в аммиачной воде для мягкого щелочного омыления оставшейся инертной непроводящей пленки Ф-4СФ.As a result, charged MF-4SK sulfonated layers of various thicknesses are formed in it, separated by an inert non-conductive F-4SF film and depending on the boiling time. The resulting film is washed with distilled water, transferred to the H ⁺ form, for subsequent synthesis of polyaniline in a charged sulfonated layer by successive exposure to a solution of 1 M protonated aniline

for 1 hour and 0.1 M ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ polymerization initiator for 1 hour, and then boiled in ammonia water for soft alkaline saponification of the remaining inert non-conductive F-4SF film.

Figure 1 is an illustration of the synthesis scheme of a composite membrane with a fixed thickness of the polyaniline layer from an inert non-conductive film F-4SF; figure 2 presents micrographs of cross sections of MF-4SK (figa) and composite membranes MF-4SK / PAn after different times of alkaline saponification of the original film F-4SF, namely: in fig.2b after 10 minutes of boiling, in fig .2c - after 20 minutes of boiling, in Fig.2d - after 40 minutes of boiling; on figa is a graph showing the dependence of the thickness of the polyaniline layer in composite membranes MF-4SK / PAn from the boiling time of the original film F-4SF, figb - the proportion of the modified layer from the total thickness of the membrane depending on the boiling time. Figure 4a shows the dependence of diffusion permeability on the concentration of HCl solution for the MF-4SK membrane (curve 1) and the MF-4SK / PAN composite membranes after 10, 20, 30, and 40 minutes of boiling the initial F-4SF film - curves 2, 3, 4, 5, respectively; on figb - the dependence of electrical conductivity on the concentration of the HCl solution for the membrane MF-4SK (curve 1) and composite membranes MF-4SK / PAN after 10, 20, 30 and 40 minutes of alkaline saponification of the original film F-4SF - curves 2, 3, 4, 5, respectively. Figure 5 - transport properties of the composite membrane MF-4SK / PAn in a 1 M HCl solution in a dimensionless form depending on the boiling time of the initial F-4SF film: curve I - diffusion permeability; curve II - electrical conductivity. 6 shows the concentration dependence of the calculated proton transfer numbers in HCl solution for MF-4SK membranes (curve 1) and the MF-4SK / PAN composite membrane after 10, 20, 30, and 40 minutes of alkaline saponification of the initial F-4SF film (curves 2- 5), curve 6 - composite membrane MF-4SK / PAn with a gradient distribution of polyaniline in accordance with RF patent No. 2411070.

Concrete example

в H⁺-форму, для последующего проведения синтеза полианилина в заряженном сульфированнном слое. Закрепив пленку между двумя полукамерами диффузионной ячейки, заливаем в одну из ее камер 1 M раствор протонированного анилина

, а в другую - дистиллированную воду. В течение 1 часа один заряженный сульфированный слой МФ-4СК насыщали ионами протонированного анилина по механизму обменной сорбции. Затем раствор протонированного анилина заменяли на полимеризующий раствор, в качестве которого был взят водный раствор 0,1 M персульфата аммония (NH₄)₂S₂O₈. Время контакта с полимеризующим раствором составляло 1 час. Образуется полианилин, который занимает весь заряженный сульфированный слой МФ-4СК. Дальнейшее прорастание цепей полианилина в объем пленки не происходит, т.к. инертный непроводящий слой Ф-4СФ в центре пленки не пропускает модифицирующие растворы. Сульфированные группы заряженного слоя МФ-4СК, образованные в результате щелочного омыления, являются допантами для ароматических цепей полианилина. Далее модифицированную полианилином пленку кипятили в водном растворе аммиака, для мягкого щелочного омыления оставшегося инертного непроводящего слоя Ф-4СФ. В результате выполнения последовательности этих действий получили композитную мембрану МФ-4СК/ПАн с фиксированной толщиной слоя полианилина и исследовали ее свойства.We take the non-conductive F-4SF film as the initial matrix, which does not have ion-exchange properties, but acquires them as a result of alkaline saponification of sulfonyl fluoride groups (-SO ₂ F) (see diagram). Alkaline saponification is carried out by boiling an inert non-conductive film F-4SF in a solution of 10% NaOH for 10 minutes. As a result, we obtain a film with charged sulfonated layers MF-4SK with a thickness of 20 μm, separated by an inert non-conductive film F-4SF (figure 1). Then the obtained film was washed with distilled water and ionogenic groups were transferred

in the H ⁺ form, for subsequent synthesis of polyaniline in a charged sulfonated layer. Having fixed the film between two half-chambers of the diffusion cell, we fill in one of its chambers a 1 M solution of protonated aniline

and to another distilled water. Within 1 hour, one charged sulfonated MF-4SK layer was saturated with protonated aniline ions by the exchange sorption mechanism. Then, the protonated aniline solution was replaced by a polymerizing solution, which was taken as an aqueous solution of 0.1 M ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ . The contact time with the polymerizing solution was 1 hour. Polyaniline is formed, which occupies the entire charged sulfonated layer of MF-4SK. Further germination of polyaniline chains in the bulk of the film does not occur, because the inert nonconducting layer of F-4SF in the center of the film does not pass modifying solutions. The sulfonated groups of the charged layer MF-4SK formed as a result of alkaline saponification are dopants for the aromatic chains of polyaniline. Next, the polyaniline-modified film was boiled in an aqueous solution of ammonia, for soft alkaline saponification of the remaining inert non-conductive layer of F-4SF. As a result of the sequence of these actions, a MF-4SK / PAn composite membrane with a fixed polyaniline layer thickness was obtained and its properties were studied.

Similarly, composite membranes MF-4SK / PAn with a fixed thickness of the polyaniline layer were obtained at different boiling times in a solution of 10% NaOH for 20, 30, 40 minutes, and their physicochemical characteristics were presented in the table.

To visualize the polyaniline layer and determine its thickness, a photo-study of sections of composite membranes MF-4SK / PAn was carried out. Analysis of photographs of sections of the MF-4SK / PAN composite membranes (Fig. 2), depending on the boiling time of the initial F-4SF film, showed that with an increase in the thickness of the charged sulfonated layer, the thickness of the polyaniline layer also increases from 20 to 40 μm in the MF-4SK composite membrane / PAn, as polyaniline occupies the entire volume of the charged sulfonated layer. It should be noted that the conditions for the synthesis of polyaniline in the MF-4SK / PAn composite membranes were identical, and the increase in the polyaniline layer was associated with an increase in boiling time of 10% NaOH, which favors the formation of a charged sulfonated MF-4SK layer.

From figure 3 a it is seen that with an increase in boiling time, the thickness of the polyaniline layer increases (from 20 to 40 μm) and reaches 25% of the thickness of the composite membrane MF-4SK / PAn with a boiling time of 40 minutes (Fig. 3 b) .

Figure 4 shows that with an increase in the thickness of the polyaniline layer in the MF-4SKUPAN composite membrane, the coefficient of diffusion permeability (P) and electrical conductivity (k) are equally reduced compared with the same characteristics for the MF-4SK membrane. From a comparison of curves 2-5 it follows that with an increase in the thickness of the polyaniline layer, the transport characteristics of the MF-4SK / PAn composite membranes decrease. The ratio of the transport characteristics of the MF-4SK / PAn composite membranes (P, k) to the similar characteristics of the MF-4SK membranes is presented in the dimensionless form (Y) in Fig. 5. With a maximum polyaniline layer thickness of 25%, the decrease in both electrical conductivity and diffusion permeability is 35% compared with the MF-4SK membrane. The noted correspondence of changes in transport characteristics is explained by the stricter geometry of the polyaniline layer. It should be noted that composite membranes with a fixed thickness of the MF-4SK / PAn polyaniline layer have higher values of proton conductivity equal to 2.7 S / m compared to composite membranes with a gradient distribution of polyaniline (0.76 S / m) made for example, in accordance with RF patent No. 2411070.

From the experimental data on the electrical conductivity (Fig. 4 a) and diffusion permeability (Fig. 4 b), using the theoretical approach described in (N.P. Gnusin, S. B. Parshikov, O. A. Demina Solution of the electrodiffusion problem transfer through the ion exchange membrane at an arbitrary concentration of the external solution. // Electrochemistry. 1998. T.34, No. 11. S.1316-1319) were calculated "true" proton transfer numbers, presented in Fig.6. From Fig.6 it is seen that composite membranes with a fixed thickness of the polyaniline layer have a high selectivity to protons (1-0.98). Composite membranes MF-4SK / PAn with a gradient distribution of polyaniline have lower proton transfer numbers (0.99-0.92), manufactured, for example, in accordance with RF patent No. 2411070.

Based on the foregoing, we can conclude that the composite membranes MF-4SKUPAN obtained by the proposed method have high electrical conductivity and selectivity, i.e. technical result is achieved. The inventive method has novelty, significant differences and is industrially applicable.

Claims (1)

A method of producing a composite membrane with a fixed polyaniline layer thickness, including the synthesis of polyaniline in a matrix by sequential exposure to a 1 M solution of protonated aniline

for 1 h and a polymerization initiator of 0.1 M ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ for 1 h, characterized in that an inert non-conductive film of a tetrafluoroethylene copolymer and perfluoro (3,6-dioxo- 4-methyl-7-octene) sulfonyl fluoride and is subjected to boiling in a solution of 10% NaOH for 10-40 minutes, with the formation of a charged sulfonated layer in the resulting film, which is washed with distilled water, transferred to the H ⁺ form, for subsequent synthesis of polyaniline in a charged sulfonated layer and then boil it in aqueous ammonia, for mild alkaline saponification of the remaining inert non-conductive film of a tetrafluoroethylene-perfluoro (3,6-dioxa-4-methyl-7-octene) sulfonyl fluoride copolymer.

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