A method for analyzing a dispersion of perfluorosulfonic acid resin based on saxs

Abstract

The application belongs to the field of perfluorosulfonic acid resin dispersion liquid, and particularly relates to a perfluorosulfonic acid resin dispersion liquid analysis method based on SAXS, comprising the following steps: obtaining a 2D SAXS spectrum of the perfluorosulfonic acid resin dispersion liquid based on synchrotron radiation SAXS; converting the 2D SAXS spectrum into a 1D SAXS curve graph; performing global fitting on the 1D SAXS curve graph by using a model to obtain structure parameters of the perfluorosulfonic acid resin dispersion liquid; and the model comprises one or more of Guinier-Porod model, Teubner-Strey model and Deybe-Bueche model. Compared with the prior art, the application solves the problem that there is no method for precise global fitting of the scattering curve in the prior art, and the obtained structure data is limited; and the structure information of the perfluorosulfonic acid aggregate morphology, size, and correlation distance between aggregates in the perfluorosulfonic acid resin dispersion liquid is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of perfluorosulfonic acid resin dispersion, and particularly relates to a SAXS-based analysis method for perfluorosulfonic acid resin dispersion. BACKGROUND

[0002] Perfluorosulfonic acid resin is a key material for proton exchange membrane and fuel cell catalyst layer, and its aggregation morphology, aggregate size and arrangement state in a solvent directly affect the film quality of the proton exchange membrane. Therefore, researchers gradually realize the importance of studying the properties of perfluorosulfonic acid resin dispersion.

[0003] Previous studies have used small-angle scattering technology and various fitting models to characterize the size, shape and surface properties of aggregates in perfluorosulfonic acid resin dispersion. However, previous studies have focused more on the extraction of perfluorosulfonic acid resin aggregate size in the high-q (scattering vector) region, and lack global fitting of the scattering curve.

[0004] In addition, a single model fitting method has limitations in interpreting SAXS data, resulting in incomplete structure analysis. Compared with small-angle scattering experiments, precise global fitting of the scattering curve is more important. Therefore, it is necessary to continue to explore and try combinations of multiple scattering models to achieve complete fitting of scattering data and obtain more reasonable and physically meaningful structures. SUMMARY

[0005] The purpose of the present application is to provide a SAXS-based analysis method for perfluorosulfonic acid resin dispersion to solve at least one of the above problems, to solve the problem of lack of precise global fitting of the scattering curve in the prior art, and to obtain limited structure data; and to achieve the acquisition of structure information such as perfluorosulfonic acid aggregate morphology, size, and inter-aggregate distance in perfluorosulfonic acid resin dispersion.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A SAXS-based analysis method for perfluorosulfonic acid resin dispersion, comprising the following steps:

[0008] S1: obtaining a 2D SAXS spectrum of perfluorosulfonic acid resin dispersion based on synchrotron SAXS;

[0009] S2: converting the 2D SAXS spectrum obtained in step S1 into a 1D SAXS curve graph;

[0010] S3: performing global fitting on the 1D SAXS curve graph obtained in step S2 using a model to obtain structure parameters of the perfluorosulfonic acid resin dispersion;

[0011] The model includes one or more of a Guinier-Porod model, a Teubner-Strey model, and a Deybe-Bueche model.

[0012] Preferably, the synchrotron SAXS is detected in a transmission mode, with conditions including an X-ray energy of 10 keV, a distance between the sample and the detector of 2000-4000 mm, and a detection range of the scattering vector of

[0013] Preferably, the model is a multi-scale Unified fitting model, which is obtained by combining a plurality of Guinier-Porod models, and is used for fitting of a multi-scale structure system, with a fitting formula as shown in formula (1):

[0014]

[0015] In formula (1), I(q) is the scattering intensity, n is the number of multi-scales of the multi-scale structure system, R gi is the mean square radius of gyration, P i is the Porod fractal dimension, G i and B i are both pre-factors, and q is the scattering vector.

[0016] Preferably, the model is a DB+TS+UF combined model, including:

[0017] The scattering signal of the scattering vector in the range of is fitted by the Guinier-Porod model; the scattering signal of the scattering vector in the range of is fitted by the Teubner-Strey model; and the scattering signal of the scattering vector in the range of is fitted by the Deybe-Bueche model. The scattering signal of the scattering vector at the end value of the range can be fitted by any one of the two models containing the point value, for example, the scattering signal at q=0.01 A-1 can be fitted by the Guinier-Porod model or the Teubner-Strey model.

[0018] Preferably, the fitting formula of the Guinier-Porod model is as shown in formula (2):

[0019]

[0020] In formula (2), I(q) is the scattering intensity, R g1 is the gyration radius, P1 is the surface fractal dimension, G and B are both pre-factors, and q is the scattering vector.

[0021] ​The fitting formula of the Teubner-Strey model is shown as formula (3):

[0022]

[0023] In formula (3), I(q) is the scattering intensity, is the volume percentage of the perfluorosulfonic acid resin in the dispersion, Δρ is the contrast, ξ TS is the correlation length, q is the scattering vector, B is the incoherent scattering background, a2, c1 and c2 are all fitting parameters of the Teubner-Strey model;

[0024] The fitting formula of the Deybe-Bueche model is shown as formula (4):

[0025]

[0026] In formula (4), I(q) is the scattering intensity, is the volume percentage of the perfluorosulfonic acid resin in the dispersion, Δρ is the contrast, ξ DB is the correlation distance of the large-size aggregate, q is the scattering vector.

[0027] Preferably, the gyration radius R g1 and the surface fractal dimension P1 are obtained by the Guinier-Porod model; TS , the inter-particle distance d TS and the amphiphilicity strength f a are obtained by the Teubner-Strey model; and the correlation length ξ DB of the large-size aggregate is obtained by the Deybe-Bueche model.

[0028] wherein,

[0029] The correlation length ξ TS is obtained by formula (3-1):

[0030]

[0031] The inter-particle distance d TS is obtained by formula (3-2):

[0032]

[0033] The amphiphilicity strength f a is obtained by formula (3-3):

[0034]

[0035] Preferably, the mass percentage of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin dispersion is 0.01-90wt%, and the rest is the dispersion solvent.

[0036] More preferably, the mass percentage of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin dispersion is 0.1-40wt%, and the rest is the dispersion solvent.

[0037] Further preferably, the mass percentage of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin dispersion is 0.2-35wt%, and the rest is the dispersion solvent.

[0038] Preferably, the dispersion solvent comprises water and a second solvent, wherein the mass percentage of water in the dispersion solvent is 5-95%, and the rest is the second solvent.

[0039] More preferably, the dispersion solvent comprises water and a second solvent, wherein the mass percentage of water in the dispersion solvent is 20-80%, and the rest is the second solvent.

[0040] Preferably, the second solvent comprises one or more of methanol, ethanol, isopropanol, n-propanol, ethylene glycol, propylene glycol, glycerol, N,N-dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone and dimethylacetamide.

[0041] Preferably, the second solvent comprises one or more of ethanol, isopropanol, n-propanol and N,N-dimethylformamide.

[0042] Preferably, the second solvent comprises one or more of methanol, ethanol, isopropanol, n-propanol, ethylene glycol, propylene glycol, glycerol, N,N-dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone and dimethylacetamide.

[0043] Preferably, the perfluorosulfonic acid resin dispersion is filled in a high-boron glass capillary for SAXS detection by synchrotron radiation.

[0044] The working principle of the present application is as follows:

[0045] First, the perfluorosulfonic acid resin is uniformly blended with the dispersion solvent to configure the perfluorosulfonic acid resin dispersion to be determined, and the dispersion is transferred to a high-boron glass capillary. Then, the capillary is placed in a test chamber filled with He gas for SAXS test. After the test, the SAXS data is converted into a 1D curve by using Igor software, and the data is analyzed by using a related model to obtain the structure information of the perfluorosulfonic acid aggregate in the dispersion, such as the shape, size and correlation distance between aggregates.

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] 1. A method for analyzing perfluorosulfonic acid resin dispersion by SAXS, which is universal and can be used to study the properties of perfluorosulfonic acid resin dispersion from very dilute solution to viscous or even gel dispersion.

[0048] 2. The combination of the multiscale Unified fitting model and the Deybe-Bueche+Teubner-Strey+Guinier-Porod (DB+TS+UF) combined model can comprehensively analyze SAXS data and obtain more detailed information about the structure of the dispersion. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 1D SAXS graph of the perfluorosulfonic acid resin dispersion prepared for Example 1 and fitted by the multiscale Unified fitting model;

[0050] Figure 2 1D SAXS graph of the perfluorosulfonic acid resin dispersion prepared for Example 2 and fitted by the DB+TS+UF combined model;

[0051] Figure 3 1D SAXS graph of the perfluorosulfonic acid resin dispersion prepared for Examples 3-5 and fitted by the multiscale Unified fitting model. DETAILED DESCRIPTION

[0052] The present application will be described in detail below with reference to the accompanying drawings and specific examples.

[0053] In the following examples, unless otherwise specified, the reagents used are conventional commercially available products, and the methods used are well-known in the art.

[0054] Example 1

[0055] A method for analyzing perfluorosulfonic acid resin dispersion by SAXS, comprising the following steps:

[0056] (1) Preparation of perfluorosulfonic acid resin dispersion: First, 1 mL of mixed solvent is prepared by mixing water and ethanol in a mass ratio of 3:1, then 2 mg of perfluorosulfonic acid resin is added to the mixed solvent, and the mixture is stirred magnetically at room temperature for 90 min to obtain a 2 mg / mL perfluorosulfonic acid resin dispersion. After standing for 24 h, the dispersion is filtered with a 0.22 um PTFE filter head for use.

[0057] (2) The perfluorosulfonic acid resin dispersion is transferred to a high boron glass capillary for SAXS testing. Test conditions: transmission model, X-ray energy 10 keV, data acquisition 2 min, sample and detector distance fixed at 3579 mm.

[0058] (3) Using Igor software to convert 2D SAXS pattern into 1D SAXS curve, and using multi-scale Unified fitting model to obtain the structure parameters of the dispersion, including surface fractal dimension P1, the gyration radius R of the rod-like aggregate in the radial direction g1 , mass fractal dimension P2, the gyration radius R of the rod-like aggregate in the radial direction g2 , inter-particle coherent distance d UF .

[0059] Example 2

[0060] A method for analyzing perfluorosulfonic acid resin dispersion by SAXS, comprising the following steps:

[0061] (1) Preparation of perfluorosulfonic acid resin dispersion: first, 1 mL of mixed solvent is prepared by mixing water and ethanol in a mass ratio of 3:1, then 2 mg of perfluorosulfonic acid resin is added to the mixed solvent, and magnetic stirring is carried out at room temperature for 90 min to obtain a 2 mg / mL perfluorosulfonic acid resin dispersion, which is filtered with a 0.22 um PTFE filter head after standing for 24 h.

[0062] (2) The perfluorosulfonic acid resin dispersion is transferred to a high boron glass capillary for SAXS test. Test conditions: transmission model, X-ray energy 10 keV, data acquisition 2 min, sample and detector distance fixed at 3579 mm.

[0063] (3) Using Igor software to convert 2D SAXS pattern into 1D SAXS curve, and using DB+TS+UF combined model to obtain the structure parameters of the dispersion, including gyration radius R g1 and surface fractal dimension P1, correlation length ξ TS and inter-particle distance d TS and amphiphilic strength f a , correlation length ξ DB of large-size aggregates.

[0064] Example 3

[0065] A method for analyzing perfluorosulfonic acid resin dispersion by SAXS, comprising the following steps:

[0066] (1) Preparation of perfluorosulfonic acid resin dispersion: first, 1 mL of mixed solvent is prepared by mixing water and ethanol in a mass ratio of 1:1, then 2 mg of perfluorosulfonic acid resin is added to the mixed solvent, and magnetic stirring is carried out at room temperature for 90 min to obtain a 2 mg / mL perfluorosulfonic acid resin dispersion, which is filtered with a 0.22 um PTFE filter head after standing for 24 h.

[0067] (2) The perfluorosulfonic acid resin dispersion liquid is transferred to a high boron glass capillary for SAXS testing. Test conditions: transmission model, X-ray energy 10 keV, data collection 2 min, sample and detector distance fixed at 3579 mm.

[0068] (3) The 2D SAXS pattern is converted into a 1D SAXS curve graph using Igor software, and the dispersion liquid structure parameters are obtained by fitting using a multi-scale Unified fitting model.

[0069] Example 4

[0070] A method for analyzing perfluorosulfonic acid resin dispersion liquid by SAXS, comprising the following steps:

[0071] (1) Preparation of perfluorosulfonic acid resin dispersion liquid: first, 1 mL of mixed solvent is prepared by mixing water and ethanol in a mass ratio of 1:1, then 10 mg of perfluorosulfonic acid resin is added to the mixed solvent, and magnetic stirring is carried out at room temperature for 90 min to obtain a 10 mg / mL perfluorosulfonic acid resin dispersion liquid, which is filtered with a 0.22 um PTFE filter head after standing for 24 h.

[0072] (2) The perfluorosulfonic acid resin dispersion liquid is transferred to a high boron glass capillary for SAXS testing. Test conditions: transmission model, X-ray energy 10 keV, data collection 2 min, sample and detector distance fixed at 3579 mm.

[0073] (3) The 2D SAXS pattern is converted into a 1D SAXS curve graph using Igor software, and the dispersion liquid structure parameters are obtained by fitting using a multi-scale Unified fitting model.

[0074] Example 5

[0075] A method for analyzing perfluorosulfonic acid resin dispersion liquid by SAXS, comprising the following steps:

[0076] (1) Preparation of perfluorosulfonic acid resin dispersion liquid: first, 1 mL of mixed solvent is prepared by mixing water and ethanol in a mass ratio of 1:1, then 20 mg of perfluorosulfonic acid resin is added to the mixed solvent, and magnetic stirring is carried out at room temperature for 90 min to obtain a 20 mg / mL perfluorosulfonic acid resin dispersion liquid, which is filtered with a 0.22 um PTFE filter head after standing for 24 h.

[0077] (2) The perfluorosulfonic acid resin dispersion liquid is transferred to a high boron glass capillary for SAXS testing. Test conditions: transmission model, X-ray energy 10 keV, data collection 2 min, sample and detector distance fixed at 3579 mm.

[0078] (3) Using Igor software to convert 2D SAXS pattern into 1D SAXS curve, and using multi-scale Unified fitting model to obtain the structure parameters of the dispersion.

[0079] SAXS data specific fitting method:

[0080] 1. Multi-scale Unified fitting model:

[0081] Multi-scale Unified (UF) fitting model is to integrate multiple Guinier-Porod models, which is suitable for systems with multi-scale structure. The fitting formula is shown in formula (1). Using formula (1) to globally fit the SAXS data, the surface fractal dimension P1, the radius of gyration R g1 of the rod-like aggregate in the radial direction, the mass fractal dimension P2, the radius of gyration R g2 of the rod-like aggregate in the radial direction, and the inter-particle coherent distance d, etc. structure parameters are obtained.

[0082]

[0083] Where I(q) is the scattering intensity, n is the number of multi-scale in the system, here n=3. R gi is the mean square radius of gyration, P i is the Porod fractal dimension, G i and B i are both pre-factors, and q is the scattering vector.

[0084] 2. DB+TS+UF model fitting method:

[0085] Perfluorosulfonic acid resin is composed of hydrophobic main chain and hydrophilic side chain, and its amphiphilicity determines that perfluorosulfonic acid resin forms microemulsion in dispersion. Teubner-Strey model is originally used to study the phase separation behavior and microstructure order of microemulsion. Therefore, this model is suitable for the study of perfluorosulfonic acid resin dispersion.

[0086] (1) The relevant model formula is as follows:

[0087] 1) The relevant formula of Guinier-Porod model is shown in formula (2):

[0088]

[0089] In formula (2), I(q) is the scattering intensity, R g1 is the radius of gyration, P1 is the surface fractal dimension, G and B are both pre-factors, and q is the scattering vector.

[0090] 2) The relevant formula of Teubner-Strey (TS) model is shown in formula (3):

[0091]

[0092] In equation (3), I(q) is the scattering intensity. ρ is the volume percentage of perfluorosulfonic acid resin in the dispersion, Δρ is the contrast, B is the incoherent scattering background, a2, c1 and c2 are the fitting parameters used in the Teubner-Strey model, and q is the scattering vector.

[0093] Further using equations (3-1) to (3-3), the relevant length ξ can be obtained. TS and interparticle distance d TS and the strength of amphipathy f a :

[0094] in,

[0095] Relevant length ξ TS We obtain the following from equation (3-1):

[0096]

[0097] interparticle distance d TS We obtain the following from equation (3-2):

[0098]

[0099] amphiphilic strength f a We obtain the following from equation (3-3):

[0100]

[0101] 3) The relevant formulas for the Debye-Bueche (DB) model are shown in equation (4):

[0102]

[0103] In equation (4), I(q) is the scattering intensity. ρ is the volume percentage of perfluorosulfonic acid resin in the dispersion, Δρ is the contrast ratio, and ξ is the volume percentage of perfluorosulfonic acid resin in the dispersion. DB q represents the relevant distance, and q is the scattering vector.

[0104] (2) Fitting process of combined model:

[0105] Step 1: Fit using the Guinier-Porod model The scattering signal within a certain range is used to obtain the cyclotron radius R. g1 and surface fractal dimension P1;

[0106] Step 2: Fit using the Teubner-Strey model From the scattered signal within the range, the correlation length ξ is obtained.TS and inter-particle distance d TS and amphiphilicity strength f a ;

[0107] Step 3: Fitting with Debye-Bueche model range of scattering signals, the correlation length ξ of large-size aggregates was obtained DB .

[0108] As shown in Figure 1 and Figure 2 , the perfluorosulfonic acid resin dispersion solution of 2 mg / mL was prepared in Example 1-2, and 1D SAXS scattering diagram was obtained by testing with the SAXS device. The data fitting was performed with the multi-scale Unified fitting model and the DB+TS+UF model, respectively. It was found that both fitting models could perform high-precision fitting on the SAXS global curve, and complementary structural parameters were obtained, so as to more comprehensively analyze the structure of the perfluorosulfonic acid resin dispersion solution. The perfluorosulfonic acid resin self-assembled into a rod-shaped particle configuration in the water / ethanol mixed solvent, the R g1 of the rod-shaped particle was 1.1 nm, the R g2 was 6 nm, the inter-particle correlation distance d UF and d TS were 41.1 nm and 48.3 nm, respectively, the particle correlation length ξ TS was 16 nm, the amphiphilicity parameter f a was -0.6, and the correlation length ξ DB of the large-size aggregates was 42 nm.

[0109] As shown in Figure 3 , the perfluorosulfonic acid resin dispersion solutions of different concentrations prepared in Example 3-5 were tested with the SAXS device to obtain 1D SAXS scattering diagram, and the multi-scale Unified fitting model was used for analysis. It was found that in the high-alcohol solvent system, the mass fractal dimension P2 was 1.38, which deviated from the rigid rod-shaped particle (P2 was 1), which indicated that the high-alcohol solvent system could induce the formation of flexible rod-shaped particles, and with the increase of the concentration, the mass fractal dimension P2 increased, and the inter-rod particle distance d UF decreased, which indicated that from the dilute solution to the concentrated solution, the monodisperse rod-shaped particles were self-assembled into a network structure by mutual overlapping.

[0110] The above description of the examples is for the convenience of the ordinary skilled in the art to understand and use the invention. Those skilled in the art can easily make various modifications to these examples, and apply the general principles described herein to other examples without creative labor. Therefore, the present application is not limited to the above examples, and the improvements and modifications made by those skilled in the art without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A method for analyzing a dispersion of perfluorosulfonic acid resin based on SAXS, characterized by, It comprises the following steps: S1: obtaining a 2D SAXS pattern of the perfluorosulfonic acid resin dispersion based on the synchrotron SAXS; S2: converting the 2D SAXS pattern obtained in step S1 into a 1D SAXS curve; S3: globally fitting the 1D SAXS curve obtained in step S2 using a model to obtain the structural parameters of the perfluorosulfonic acid resin dispersion; The model is a multiscale Unified fitting model, which is obtained by combining a plurality of Guinier-Porod models, is used for fitting of a multiscale structure system, and a fitting formula is shown as formula (1): （1）； In formula (1), I(q) is the scattering intensity, n is the number of the multi-scale quantity of the multi-scale structure system, R gi is the mean square radius of gyration, P i is the Porod fractal dimension, G i and B i are both pre-factors, and q is the scattering vector; Or, The model is a DB+TS+UF combined model, which comprises: The scattering signals in the range of scattering vectors 0.1-0.3 Å -1 are fitted by Guinier-Porod model; the scattering signals in the range of scattering vectors 0.01-0.1 Å -1 are fitted by Teubner-Strey model; the scattering signals in the range of scattering vectors 0.004-0.01 Å -1 are fitted by Deybe-Bueche model; the gyration radius R g1 and the surface fractal dimension P1 are obtained by the Guinier-Porod model; the correlation length ξ TS , the inter-particle distance d TS and the strength of amphiphilicity f a are obtained by the Teubner-Strey model; the correlation length ξ DB of the large-size aggregates is obtained by the Deybe-Bueche model.

2. The SAXS-based method for analyzing a dispersion of perfluorosulfonic acid resin according to claim 1, characterized by, The synchronous radiation SAXS is detected in a transmission mode, and the conditions include that the X-ray energy is 10 keV, the distance between the sample and the detector is 2000-4000 mm, and the detection range of the scattering vector is 0.004-0.3 Å -1 .

3. The SAXS-based method for analyzing a dispersion of perfluorosulfonic acid resin according to claim 1, characterized by, The fitting formula of the Guinier-Porod model is shown as formula (2): （2）； In formula (2), I(q) is the scattering intensity, R g1 is the gyration radius, P1 is the surface fractal dimension, G and B are pre-factors, and q is the scattering vector; The fitting formula of the Teubner-Strey model is shown as formula (3): （3）； In formula (3), I(q) is the scattering intensity, φ is the volume percentage of the perfluorosulfonic acid resin in the dispersion liquid, Δρ is the contrast, ξ TS is the correlation length, q is the scattering vector, B is the incoherent scattering background, a2, c1, and c2 are all fitting parameters of the Teubner-Strey model; The fitting formula of the Deybe-Bueche model is shown as formula (4): （4）； In formula (4), I(q) is the scattering intensity, φ is the volume percentage of the perfluorosulfonic acid resin in the dispersion liquid, Δρ is the contrast, ξ DB is the correlation distance of the large-size aggregates, and q is the scattering vector.

4. The analysis method of the perfluorosulfonic acid resin dispersion based on SAXS according to claim 3, characterized in that, Correlation length ξ TS By equation (3-1), we obtain: （3-1）； Interparticle distance d TS By equation (3-2) we obtain: （3-2）； f a By equation (3-3), we obtain: （3-3）。 5. The SAXS-based method for analyzing a dispersion of perfluorosulfonic acid resin according to claim 1, characterized by, The mass percentage of the perfluorosulfonic acid resin in the perfluorosulfonic acid resin dispersion is 0.01-90wt%, and the rest is a dispersion solvent.

6. The SAXS-based method for analyzing a dispersion of perfluorosulfonic acid resin according to claim 5, characterized by, The dispersion solvent comprises water and a second solvent, wherein the mass percentage of water in the dispersion solvent is 5-95%, and the rest is the second solvent.

7. The SAXS-based method for analyzing a dispersion of perfluorosulfonic acid resin according to claim 6, characterized by, The second solvent comprises one or more of methanol, ethanol, isopropanol, n-propanol, ethylene glycol, propylene glycol, glycerol, N,N-dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone and dimethylacetamide.

8. The SAXS-based method for analyzing a dispersion of perfluorosulfonic acid resin according to claim 1, characterized by, The perfluorosulfonic acid resin dispersion is contained in a high-boron glass capillary for synchrotron SAXS detection.

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