Pickering emulsion composition using polyimide particles and preparation method thereof

Abstract

The present invention relates to a pickering emulsion composition using polyimide particles and a method for preparing the same. The pickering emulsion stabilized by the polyimide particles according to the present invention has a very stable dispersed phase and does not cause flocculation, creaming, coalescence and phase separation even after a long time, and has an advantage of being capable of forming both an oil-in-water type emulsion and a water-in-oil type emulsion. Further, the polyimide particles used in the present invention can be synthesized in a simple manner and have partial wettability without the surface treatment and pH control so that they can be easily used for the emulsion stabilization.

Claims

1. A method of preparing a pickering emulsion composition, the method comprising: (a) dispersing and reacting a dianhydride compound and a diamine compound in water as a dispersion medium to obtain a polyimide; (b) putting the polyimide obtained in step (a) into a water phase which is a continuous phase and applying ultrasonic waves thereto so as to adjust an average particle diameter of the polyimide; and (c) adding and stirring an oil phase to the dispersion obtained in step (b).

2. A method of preparing a pickering emulsion composition, the method comprising: (a) dispersing and reacting a dianhydride compound and a diamine compound in water as a dispersion medium to obtain a polyimide; (b) putting the polyimide obtained in step (a) into an oil phase which is a continuous phase and applying ultrasonic waves thereto so as to adjust an average particle diameter of the polyimide; and (c) adding and stirring a water phase to the dispersion obtained in step (b).

3. The method according to claim 1, wherein in step (b), the ultrasonic waves are applied in 20 kHz to 100 kHz.

4. The method according to claim 1, wherein in step (b), the ultrasonic waves are applied for 10 minutes to 120 minutes.

5. The method according to claim 1, wherein in step (c), the average particle diameter of the polyimide in the dispersion obtained in step (b) is 10 nm to 20 μm.

6. The method according to claim 2, wherein in step (b), the ultrasonic waves are applied in 20 kHz to 100 kHz.

7. The method according to claim 2, wherein in step (b), the ultrasonic waves are applied for 10 minutes to 120 minutes.

8. The method according to claim 2, wherein in step (c), the average particle diameter of the polyimide in the dispersion obtained in step (b) is 10 nm to 20 μm.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates an SEM image of the polyimide particles according to the present invention.

(2) FIG. 2 illustrates a microscopic image of the pickering emulsion according to the present invention.

DESCRIPTION OF EMBODIMENTS

(3) Hereinafter, the present invention will be described in more detail with reference to Examples. It should be understood, however, that the following Examples are intended to assist the understanding of the present invention and are not intended to limit the scope of the present invention.

Synthesis Example 1. Synthesis of Wholly Aromatic Polyimide (PMDA-ODA)

(4) Pyromellitic dianhydride (PMDA, 1.09 g, 5.0 mmol) and 4,4′-oxydianiline (ODA, 1.00 g, 5.0 mmol) were dispersed in 20 mL distilled water as a dispersion medium in a 100 mL 2-neck round bottom flask which was substituted with nitrogen gas. Pyridine (2 mL, 25.0 mmol) as a catalyst and acetic anhydride (0.94 mL, 10.0 mmol) as a dehydrating agent were added thereto, and the mixture was reacted at 100° C. for 24 hours under reflux. The reaction mixture was filtered, and the obtained solid was washed with distilled water, acetone or methanol and vacuum-dried to obtain polymer powders. The synthesized polyimide particles were found to have C═O absorption bands of the imide group at 1775 cm.sup.−1 and 1725 cm.sup.−1, respectively, and C—N absorption band of the imide group at 1378 cm.sup.−1, as a result of infrared absorption spectrum analysis.

Synthesis Example 2. Synthesis of Partially Aromatic Polyimide (HPMDA-ODA)

(5) 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA, 1.12 g, 5.0 mmol) and 4,4′-oxydianiline (ODA, 1.00 g, 5.0 mmol) were dispersed in 20 mL distilled water as a dispersion medium in a 100 mL 2-neck round bottom flask which was substituted with nitrogen gas. Pyridine (2 mL, 25.0 mmol) as a catalyst and acetic anhydride (0.94 mL, 10.0 mmol) as a dehydrating agent were added thereto, and the mixture was reacted at 100° C. for 24 hours under reflux. The reaction mixture was filtered, and the obtained solid was washed with distilled water, acetone or methanol and vacuum-dried to obtain polymer powders.

Example 1. Preparation of an Oil-in-Water Type Pickering Emulsion Composition

(6) 0.1 g of the polyimide powder synthesized in Synthesis Example 1 and 50 mL of distilled water as a continuous phase were placed in a 100 mL beaker, and ultrasonic waves of 20 kHz were applied thereto for 30 minutes to uniformly disperse the polyimide particles therein. While the dispersion was stirred using a mechanical stirrer at 1,500 rpm, 8 mL of N-hexadecane, an oil phase, was added thereto, and the mixture was stirred for 10 minutes. When the stirring was stopped after 10 minutes, the N-hexadecane droplet was present in the form of an oil-in-water type emulsion with an average diameter of about 250 μm. It was confirmed that the pickering emulsion prepared using the polyimide particles was maintained for 7 days or more.

Example 2. Preparation of an Oil-in-Water Type Pickering Emulsion Composition

(7) 0.1 g of the polyimide powder synthesized in Synthesis Example 2 and 50 mL of distilled water as a continuous phase were placed in a 100 mL beaker, and ultrasonic waves of 20 kHz were applied thereto for 30 minutes to uniformly disperse the polyimide particles therein. While the dispersion was stirred using a mechanical stirrer at 1,500 rpm, 8 mL of N-hexadecane, an oil phase, was added thereto, and the mixture was stirred for 10 minutes. When the stirring was stopped after 10 minutes, the N-hexadecane droplet was present in the form of an oil-in-water type emulsion with an average diameter of about 250 μm. It was confirmed that the pickering emulsion prepared using the polyimide particles was maintained for 7 days or more.

Example 3. Preparation of a Water-in-Oil Type Pickering Emulsion Composition

(8) 0.1 g of the polyimide powder synthesized in Synthesis Example 1 and 50 mL of decalin (decahydronaphthalene) as a continuous phase were placed in a 100 mL beaker, and ultrasonic waves of 20 kHz were applied thereto for 30 minutes to uniformly disperse the polyimide particles therein. While the dispersion was stirred using a mechanical stirrer at 1,500 rpm, 8 mL of a distilled water was added thereto, and the mixture was stirred for 10 minutes. When the stirring was stopped after 10 minutes, the distilled water was present in the form of a water-in-oil type emulsion with an average diameter of about 250 μm. It was confirmed that the pickering emulsion prepared using the polyimide particles was maintained for 7 days or more.

Example 4. Preparation of a Water-in-Oil Type Pickering Emulsion Composition

(9) 0.1 g of the polyimide powder synthesized in Synthesis Example 2 and 50 mL of decalin (decahydronaphthalene) as a continuous phase were placed in a 100 mL beaker, and ultrasonic waves of 20 kHz were applied thereto for 30 minutes to uniformly disperse the polyimide particles therein. While the dispersion was stirred using a mechanical stirrer at 1,500 rpm, 8 mL of a distilled water was added thereto, and the mixture was stirred for 10 minutes. When the stirring was stopped after 10 minutes, the distilled water was present in the form of a water-in-oil type emulsion with an average diameter of about 250 μm. It was confirmed that the pickering emulsion prepared using the polyimide particles was maintained for 7 days or more.

Comparative Synthesis Example 1. Synthesis of Wholly Aromatic Polyimide (PMDA-ODA) Using an Organic Solvent

(10) 20 mL of N-methylpyrrolidone as an organic solvent was placed in a 100 mL 2-neck round bottom flask which was substituted with nitrogen gas. Pyromellitic dianhydride (PMDA, 1.09 g, 5.0 mmol) and 4,4′-oxydianiline (ODA, 1.00 g, 5.0 mmol) were added thereto, and the mixture was reacted at room temperature for 24 hours. Acetic anhydride (0.94 mL, 10.0 mmol) as a dehydrating agent and pyridine (0.8 mL, 25.0 mmol) as a catalyst were added to the solution, and the mixture was reacted at 160° C. for 6 hours under reflux to carry out an imidization reaction. The reaction was completed, and then the mixture was cooled to room temperature, followed by the reprecipitation using an excessive amount of ice water (distilled water). The precipitate was washed with distilled water, acetone or methanol and filtered, and the obtained solid was vacuum-dried to obtain polymer powders.

Comparative Synthesis Example 2. Synthesis of Partially Aromatic Polyimide (HPMDA-ODA) Using an Organic Solvent

(11) 20 mL of N-methylpyrrolidone as an organic solvent was placed in a 100 mL 2-neck round bottom flask which was substituted with nitrogen gas. 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA, 1.12 g, 5.0 mmol) and 4,4′-oxydianiline (ODA, 1.00 g, 5.0 mmol) were added thereto, and the mixture was reacted at room temperature for 24 hours.

(12) Acetic anhydride (0.94 mL, 10.0 mmol) as a dehydrating agent and pyridine (0.8 mL, 25.0 mmol) as a catalyst were added to the solution, and the mixture was reacted at 160° C. for 6 hours under reflux to carry out an imidization reaction. The reaction was completed, and then the mixture was cooled to room temperature, followed by the reprecipitation using an excessive amount of ice water (distilled water). The precipitate was washed with distilled water, acetone or methanol and filtered, and the obtained solid was vacuum-dried to obtain polymer powders.

Comparative Example 1. Preparation of an Oil-in-Water Type Pickering Emulsion Composition Using Wholly Aromatic Polyimide (PMDA-ODA) Synthesized with an Organic Solvent

(13) When 0.1 g of polyimide powder synthesized according to Comparative Synthesis Example 1 and 50 mL of distilled water as a continuous phase were placed in a 100 mL beaker, and the ultrasonic wave was applied thereto at 20 kHz for 30 minutes, the PMDA-ODA polyimide particles synthesized with an organic solvent were not dispersed uniformly in water, and most of it was precipitated. When the dispersion in which most of the polyimide particles were precipitated but only a portion of polyimide particles was dispersed was stirred at 1500 rpm and N-hexadecane, an oil phase, was added thereto, it resulted in poor emulsion stabilization. Even when the precipitated polyimide particles were removed by filtration and only the dispersion liquid was collected and tested, the emulsion stabilization was not achieved well.

Comparative Example 2. Preparation of an Oil-in-Water Type Pickering Emulsion Composition Using Partially Aromatic Polyimide (HPMDA-ODA) Synthesized with an Organic Solvent

(14) When 0.1 g of polyimide powder synthesized according to Comparative Synthesis Example 2 and 50 mL of distilled water as a continuous phase were placed in a 100 mL beaker, and the ultrasonic wave was applied thereto at 20 kHz for 30 minutes, the HPMDA-ODA polyimide particles synthesized with an organic solvent were not dispersed uniformly in water, and most of it was precipitated. When the dispersion in which most of the polyimide particles were precipitated but only a portion of polyimide particles was dispersed was stirred at 1500 rpm and N-hexadecane, an oil phase, was added thereto, it resulted in poor emulsion stabilization. Even when the precipitated polyimide particles were removed by filtration and only the dispersion liquid was collected and tested, the emulsion stabilization was not achieved well.

Comparative Example 3. Preparation of a Water-in-Oil Type Pickering Emulsion Composition Using Wholly Aromatic Polyimide (PMDA-ODA) Synthesized with an Organic Solvent

(15) When 0.1 g of polyimide powder synthesized in Comparative Synthesis Example 1 and 50 mL of decalin as a continuous phase were placed in a 100 mL beaker, and the ultrasonic wave was applied thereto at 20 kHz for 30 minutes, the PMDA-ODA polyimide particles synthesized with an organic solvent were not dispersed uniformly in decalin, and most of it was precipitated. When the dispersion in which most of the polyimide particles were precipitated but only a portion of polyimide particles was dispersed was stirred at 1500 rpm and distilled water was added thereto, it resulted in poor emulsion stabilization. Even when the precipitated polyimide particles were removed by filtration and only the dispersion liquid was collected and tested, the emulsion stabilization was not achieved well.

Comparative Example 4. Preparation of a Water-in-Oil Type Pickering Emulsion Composition Using Partially Aromatic Polyimide (HPMDA-ODA) Synthesized with an Organic Solvent

(16) When 0.1 g of polyimide powder synthesized in Comparative Synthesis Example 2 and 50 mL of decalin as a continuous phase were placed in a 100 mL beaker, and the ultrasonic wave was applied thereto at 20 kHz for 30 minutes, the HPMDA-ODA polyimide particles synthesized with an organic solvent were not dispersed uniformly in decalin, and most of it was precipitated. When the dispersion in which most of the polyimide particles were precipitated but only a portion of polyimide particles was dispersed was stirred at 1500 rpm and distilled water was added thereto, it resulted in poor emulsion stabilization. Even when the precipitated polyimide particles were removed by filtration and only the dispersion liquid was collected and tested, the emulsion stabilization was not achieved well.

Comparative Example 5-1. Preparation of an Oil-in-Water Type Pickering Emulsion Composition Using Polyimide Particles without Applying Ultrasonic Wave

(17) 0.1 g of the wholly aromatic polyimide particles (PMDA-ODA) prepared in Synthesis Example 1 was collected, and 50 mL of distilled water was added thereto. While the mixture was then stirred using a mechanical stirrer at 1,500 rpm without any additional ultrasonic wave applied, N-hexadecane as an oil phase was added thereto.

(18) The polyimide particles were not uniformly dispersed in water, and thus the pickering emulsion stabilization by N-hexadecane was not completely achieved.

Comparative Example 5-2. Preparation of an Oil-in-Water Type Pickering Emulsion Composition Using Polyimide Particles without Applying Ultrasonic Wave

(19) 0.1 g of the partially aromatic polyimide particles (HPMDA-ODA) prepared in Synthesis Example 2 was collected, and 50 mL of distilled water was added thereto. While the mixture was then stirred using a mechanical stirrer at 1,500 rpm without any additional ultrasonic wave applied, N-hexadecane as an oil phase was added thereto.

(20) The polyimide particles were not uniformly dispersed in water, and thus the pickering emulsion stabilization by N-hexadecane was not completely achieved.

Comparative Example 6-1. Preparation of a Water-in-Oil Type Pickering Emulsion Composition Using Polyimide Particles without Applying Ultrasonic Wave

(21) 0.1 g of the wholly aromatic polyimide particles (PMDA-ODA) prepared in Synthesis Example 1 was collected, and 50 mL of decalin was added thereto. While the mixture was then stirred using a mechanical stirrer at 1,500 rpm without any additional ultrasonic wave applied, distilled water was added thereto.

(22) The polyimide particles were not uniformly dispersed in water, and thus the pickering emulsion stabilization by the distilled water was not completely achieved.

Comparative Example 6-2. Preparation of a Water-in-Oil Type Pickering Emulsion Composition Using Polyimide Particles without Applying Ultrasonic Wave

(23) 0.1 g of the partially aromatic polyimide particles (HPMDA-ODA) prepared in Synthesis Example 2 was collected, and 50 mL of decalin was added thereto. While the mixture was then stirred using a mechanical stirrer at 1,500 rpm without any additional ultrasonic wave applied, distilled water was added thereto.

(24) The polyimide particles were not uniformly dispersed in water, and thus the pickering emulsion stabilization by the distilled water was not completely achieved.