Method for representing morphology of perfluorinated sulfonic acid resin dispersion liquid by using cryoelectron microscope

Abstract

The invention relates to a method for characterizing the morphology of a perfluorinated sulfonic acid resin dispersion liquid by using a cryoelectron microscope, which comprises the following steps: (1) dispersion liquid preparation: dispersing perfluorinated sulfonic acid resin powder in a solvent to obtain a uniformly dispersed perfluorinated sulfonic acid resin dispersion liquid; (2) preparing a test sample of the cryoelectron microscope: dripping a trace amount of perfluorinated sulfonic acid resin dispersion liquid on a carrier net for the cryoelectron microscope, waiting for several seconds, removing redundant dispersion liquid, then transferring the dispersion liquid into liquid ethane for rapid cooling, and locking the structure of the dispersion liquid; and (3) testing with a cryoelectron microscope: transferring the frozen sample to a test rod for the cryoelectron microscope, and sending the sample to a cooling bin for testing. Compared with the prior art, the cryoelectron microscope characterization method provided by the invention has the advantage that the form and size information of the perfluorosulfonic acid aggregate in the dispersion liquid can be intuitively observed.

Description

Technical Field

[0001] The invention relates to the technical field of perfluorosulfonic acid resin dispersion liquid, and in particular to a method for characterizing the morphology of perfluorosulfonic acid resin dispersion liquid by using a cryo-electron microscope. Background Art

[0002] Perfluorosulfonic acid resin is a key material for proton exchange membranes. It was originally developed by Dr. Walther Grot of Dupont Corporation in the United States. In 1982, Dr. Grot proposed that perfluorosulfonic acid resin can be evenly dispersed in a water / alcohol mixed solvent under high temperature and high pressure, and a proton exchange membrane with uniform thickness and good performance was prepared by solution casting. After that, solution casting became one of the main methods for preparing proton exchange membranes. The morphology of the proton membrane prepared by solution casting has an inheritance relationship with the microstructure of the initial perfluorosulfonic acid resin dispersion, so the study of the microstructure of the perfluorosulfonic acid resin dispersion has become an important topic in the field of proton exchange membranes.

[0003] At present, there is little research on the microstructure of perfluorosulfonic acid resin dispersions, and there is a lack of systematic understanding of the aggregate structure and self-assembly behavior in the dispersion. Summary of the invention

[0004] The purpose of the present invention is to provide a method for characterizing the morphology of a perfluorosulfonic acid resin dispersion using a cryo-electron microscope, which can intuitively observe the morphology and size of aggregates in the dispersion.

[0005] The purpose of the present invention can be achieved by the following technical solution: A method for characterizing the morphology of a perfluorosulfonic acid resin dispersion using a cryo-electron microscope comprises the following steps:

[0006] (1) Preparation of dispersion: dispersing perfluorosulfonic acid resin powder in a solvent to obtain a uniformly dispersed perfluorosulfonic acid resin dispersion;

[0007] (2) Preparation of cryo-EM test samples: drop a small amount of perfluorosulfonic acid resin dispersion onto the cryo-EM grid, wait for a few seconds, remove the excess dispersion, and then transfer it to liquid ethane for rapid cooling to lock the dispersion structure;

[0008] (3) Cryo-electron microscopy test: The frozen sample is transferred to the test rod for cryo-electron microscopy, and the sample is sent to the cooling chamber for morphology testing.

[0009] Preferably, in the perfluorosulfonic acid resin dispersion of step (1), the mass percentage of the perfluorosulfonic acid resin is 0.01-50wt%.

[0010] Further preferably, in the perfluorosulfonic acid resin dispersion, the mass percentage of the perfluorosulfonic acid resin is 0.05-10wt%.

[0011] More preferably, in the perfluorosulfonic acid resin dispersion, the mass percentage of the perfluorosulfonic acid resin is 0.1-3wt%.

[0012] Preferably, the perfluorosulfonic acid resin dispersion is filtered through a 0.22 um PTFE filter.

[0013] Preferably, the solvent in step (1) is a blend of water and an organic solvent, wherein water accounts for 5-95 wt % of the total solvent.

[0014] Further preferably, the solvent in step (1) is a blend of water and an organic solvent, wherein water accounts for 20-80 wt % of the total solvent.

[0015] Further preferably, it is characterized in that the organic solvent is one or more of methanol, ethanol, isopropanol, n-propanol, ethylene glycol, propylene glycol, glycerol, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and dimethylacetamide.

[0016] More preferably, the organic solvent is a mixture of one or more of ethanol, isopropanol, n-propanol and N,N-dimethylformamide.

[0017] Further preferably, the mass percentage of the organic solvent to the total solvent is 5-95wt%, preferably 20-80wt%.

[0018] Preferably, the trace amount of perfluorosulfonic acid resin dispersion in step (2) is 0.5-10 uL.

[0019] Further preferably, the trace amount of perfluorosulfonic acid resin dispersion in step (2) is 1-3 uL.

[0020] Preferably, the grid for cryo-electron microscopy in step (2) is a 100-500 mesh carbon mesh.

[0021] Further preferably, the grid for cryo-electron microscopy in step (2) is a 300-400 mesh carbon mesh.

[0022] Preferably, after waiting for 1-3 seconds in step (2), excess dispersion is sucked off with filter paper.

[0023] Preferably, the temperature of the liquid ethane in step (2) is -160 to -170°C.

[0024] Preferably, the rapid cooling time in liquid ethane in step (2) is 10 s-10 min.

[0025] Further preferably, the rapid cooling time in liquid ethane in step (2) is 3-5 min.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention proposes a method for characterizing a perfluorosulfonic acid resin dispersion using a cryo-electron microscope, which can intuitively observe the morphology and size of aggregates in the dispersion;

[0028] 2. The present invention proposes a method for characterizing a perfluorosulfonic acid resin dispersion using a cryo-electron microscope, which can intuitively observe the self-assembly process of perfluorosulfonic acid resin aggregates from a dilute solution to a concentrated solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a cryo-electron micrograph of the EW700 short-chain perfluorosulfonic acid resin dispersion prepared in Example 1;

[0030] Figure 2 This is a cryo-electron micrograph of the EW700 short-chain perfluorosulfonic acid resin dispersion prepared in Example 2;

[0031] Figure 3 This is a cryo-electron microscopy image of the EW900 long-chain branched perfluorosulfonic acid resin dispersion prepared in Example 3. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0033] First, the perfluorosulfonic acid resin and the dispersing solvent are uniformly mixed to obtain a perfluorosulfonic acid resin dispersion; then 1-3uL of the dispersion is dropped on the grid for cryo-electron microscopy. After standing for 1-3s, the excess dispersion is removed with filter paper, and the sample is quickly transferred to -160 to -170℃ low-temperature liquid ethane to quickly cool and lock the dispersion morphology; finally, the prepared sample is placed on the sample rod for cryo-electron microscopy and transferred to the freezing chamber for morphology testing.

[0034] The following describes it in detail with reference to specific embodiments.

[0035] Example 1

[0036] A method for characterizing the morphology of a perfluorosulfonic acid resin dispersion using a cryo-electron microscope comprises the following steps:

[0037] (1) Preparation of perfluorosulfonic acid resin dispersion: First, water and ethanol were prepared in a mass ratio of 3:1 to prepare 99.8 mg of a mixed solvent, and then 0.2 mg of EW700 short-chain branched perfluorosulfonic acid resin (purchased from Dongyue Shenzhou New Energy Co., Ltd.) was added to the mixed solvent, and magnetic stirring was performed at room temperature for 90 min to obtain a 0.2 wt% perfluorosulfonic acid resin dispersion. After standing for 24 h, the dispersion was filtered with a 0.22 um PTFE filter head for use;

[0038] (2) Drop 2uL of perfluorosulfonic acid resin dispersion on a 300-mesh carbon mesh, let it stand for 1 second, remove the excess dispersion with filter paper, and then quickly transfer it to -160 to -170°C liquid ethane and quickly cool it for 3 minutes to obtain a test sample;

[0039] (3) The sample was quickly transferred to a cryo-EM sample holder and then placed in a cryo-EM chamber for cryo-EM testing (Talos F200C G2 field emission cryo-EM) to obtain a dispersion morphology image at an accelerating voltage of 200 kV.

[0040] Example 2

[0041] A method for characterizing the morphology of a perfluorosulfonic acid resin dispersion using a cryo-electron microscope comprises the following steps:

[0042] (1) Preparation of perfluorosulfonic acid resin dispersion: First, water and ethanol were prepared in a mass ratio of 3:1 to prepare 98 mg of a mixed solvent, and then 2 mg of EW700 short-chain perfluorosulfonic acid resin (purchased from Dongyue Shenzhou New Energy Co., Ltd.) was added to the mixed solvent, and magnetic stirring was performed at room temperature for 90 min to obtain a 2 wt% perfluorosulfonic acid resin dispersion. After standing for 24 h, the dispersion was filtered with a 0.22 um PTFE filter head for use;

[0043] (2) Drop 2uL of perfluorosulfonic acid resin dispersion on a 300-mesh carbon mesh, let it stand for 1 second, remove the excess dispersion with filter paper, and then quickly transfer it to -160 to -170°C liquid ethane and quickly cool it for 3 minutes to obtain a test sample;

[0044] (3) The sample was quickly transferred to a cryo-EM sample holder and then placed in a cryo-EM chamber for cryo-EM testing (Talos F200C G2 field emission cryo-EM) to obtain a dispersion morphology image at an accelerating voltage of 200 kV.

[0045] Example 3

[0046] A method for characterizing the morphology of a perfluorosulfonic acid resin dispersion using a cryo-electron microscope comprises the following steps:

[0047] (1) Preparation of perfluorosulfonic acid resin dispersion: First, water and ethanol were prepared in a mass ratio of 3:1 to prepare 99.8 g of a mixed solvent, and then 0.2 mg of EW900 long-chain branched perfluorosulfonic acid resin (Nafion D2020) was added to the mixed solvent. The mixture was stirred magnetically at room temperature for 90 min to obtain a 0.2 wt% perfluorosulfonic acid resin dispersion. After standing for 24 h, the dispersion was filtered using a 0.22 um PTFE filter for later use.

[0048] (2) Drop 2uL of perfluorosulfonic acid resin dispersion on a 300-mesh carbon mesh, let it stand for 1 second, remove the excess dispersion with filter paper, and then quickly transfer it to -160 to -170°C liquid ethane and quickly cool it for 3 minutes to obtain a test sample;

[0049] (3) The sample was quickly transferred to a cryo-EM sample holder and then placed in a cryo-EM chamber for cryo-EM testing (Talos F200C G2 field emission cryo-EM) to obtain a dispersion morphology image at an accelerating voltage of 200 kV.

[0050] The cryo-EM image of the 0.2wt% EW700 short-chain branched perfluorosulfonic acid resin dispersion prepared in Example 1 shows that the EW700 short-chain branched perfluorosulfonic acid resin forms a monodisperse rod-like structure in a water / ethanol blended solvent, with an average radius and length of 1.47nm and 18.83nm, respectively. The cryo-EM image of the 2wt% EW700 short-chain branched perfluorosulfonic acid resin dispersion prepared in Example 2 shows that as the concentration increases, the monodisperse rod-like particles overlap with each other to form a densely arranged network structure. The cryo-EM image of the 0.2wt% EW900 long-chain branched perfluorosulfonic acid resin prepared in Example 3 shows that the EW900 long-chain branched perfluorosulfonic acid resin not only forms monodisperse primary rod-like particles in a water / ethanol system, but also has large-sized secondary aggregates composed of primary rod-like particles.

[0051] The present invention uses cryo-electron microscopy technology to intuitively observe key structural information such as the aggregation morphology and size of perfluorosulfonic acid resin in the solvent, which is expected to promote the development of the dispersion research field.

[0052] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy, characterized in that, it includes the following steps: (1) Dispersion preparation: Disperse perfluorosulfonic acid resin powder in a solvent to obtain a uniformly dispersed perfluorosulfonic acid resin dispersion; (2) Preparation of cryo-electron microscopy test sample: Drop a small amount of perfluorosulfonic acid resin dispersion on a grid for cryo-electron microscopy. After waiting for several seconds, remove the excess dispersion, and then transfer it to liquid ethane for rapid cooling to lock the structure of the dispersion; (3) Cryo-electron microscopy test: Transfer the frozen sample to a test rod for cryo-electron microscopy and send the sample to a cooling chamber for testing.

2. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 1, characterized in that, in the perfluorosulfonic acid resin dispersion described in step (1), the mass percentage of perfluorosulfonic acid resin is 0.01 - 50 wt%.

3. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 1, characterized in that, the solvent described in step (1) is a blend of water and an organic solvent, where water accounts for 5 - 95 wt% of the total solvent, and the organic solvent accounts for 5 - 95 wt% of the total solvent.

4. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 3, characterized in that, the organic solvent is one or a blend of methanol, ethanol, isopropanol, n-propanol, ethylene glycol, propylene glycol, glycerol, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, dimethylacetamide.

5. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 4, characterized in that, the organic solvent is one or a blend of ethanol, isopropanol, n-propanol, N,N-dimethylformamide.

6. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 1, characterized in that, the small amount of perfluorosulfonic acid resin dispersion described in step (2) is 0.5 - 10 uL.

7. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 1, characterized in that, the grid for cryo-electron microscopy described in step (2) is a 100 - 500 mesh reticulated carbon grid.

8. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 1, characterized in that, after waiting for 1 - 3 s in step (2), use filter paper to suck off the excess dispersion.

9. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 1, characterized in that, the temperature of the liquid ethane described in step (2) is -160 to -170 °C.

10. The method for characterizing the morphology of perfluorosulfonic acid resin dispersion by cryo-electron microscopy according to claim 1, characterized in that, the time for rapid cooling in liquid ethane in step (2) is 10 s - 10 min.

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