Phosphate ester-based dopant for polyaniline dispersion, method for preparing the same, and aqueous polyaniline dispersion

Abstract

The application belongs to the technical field of polyaniline, and provides a phosphate ester dopant for polyaniline dispersion, a preparation method thereof and a polyaniline aqueous dispersion, wherein the phosphate ester dopant has a structure of formula I; wherein z, m and n are all polymerization degrees, and m+n is an integer selected from 1-10. The application mainly utilizes the introduction of ester bonds and ether bonds to successfully control the hydrophilicity of the dopant, so that the hydrophilicity of the aqueous polyaniline can be reduced for polyaniline dispersion, which is beneficial to the water processing of polyaniline and the improvement of water resistance. In addition, the application utilizes the hydrophilic polyethylene glycol monomethyl ether to initiate the polymerization of carbon dioxide and propylene oxide to prepare a dopant precursor, and the phosphate ester dopant is obtained through a simple phosphorylation reaction, and the preparation method is simple and easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of polyaniline technology, and specifically relates to a phosphate ester dopant for polyaniline dispersion, its preparation method, and a polyaniline aqueous dispersion. Background Technology

[0002] Polyaniline is an important conductive polymer with crucial applications in metal corrosion protection and electromagnetic shielding materials. Polyaniline has the structure shown in the following formula, comprising reducing and oxidizing units. Its long-chain conjugated structure makes it highly prone to aggregation, hindering liquid-phase processing.

[0003]

[0004] To achieve solution processing of polyaniline, ion-induced methods have been developed and applied. Conventional methods involve doping polyaniline with organic or inorganic acids to form a polyaniline dispersion solution, thereby enabling solution processing. The mainstream technology for polyaniline solution processing primarily uses organic solvents, which clearly fails to meet environmental protection requirements. Using water as a solvent for polyaniline processing is still in the research stage and faces issues such as water resistance.

[0005] Existing technologies have reported a strategy to address the water resistance problem of water-based polyaniline by shortening the aqueous segments in the dopant (Jing Luo, Hongming Zhang, Xianhong Wang, Ji Li, and Fosong Wang. Macromolecules, 2007, 40, 23, 8132-8135). This involves reacting diethylene glycol monomethyl ether with phosphorus oxychloride to prepare a mono- and diester-mixed phosphate ester dopant with the structure shown in formula (1) or (2), which is then used to dope polyaniline to obtain a water-dispersible polyaniline solution. Although this technology achieves the transformation of water-based polyaniline processing from aqueous solution to water dispersion, the dopant used is a water-soluble molecule, and certain water resistance issues still exist.

[0006] Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides a phosphate ester dopant for polyaniline dispersion, its preparation method, and a polyaniline aqueous dispersion. Using the phosphate ester dopant described in the present invention, a polyaniline aqueous dispersion with improved water resistance can be formed, which is beneficial for application.

[0008] This invention provides a phosphate ester dopant for dispersing polyaniline, wherein the phosphate ester dopant has the structure of Formula I:

[0009]

[0010] Where z, m, and n are all aggregation degrees, and m+n is selected from integers between 1 and 10.

[0011] In an embodiment of the present invention, the phosphate ester dopant exists in the form of nanomicelles in water.

[0012] This invention provides a method for preparing phosphate ester dopants as described above, comprising:

[0013] The polymer shown in Formula II is phosphorylated with phosphorus pentoxide to obtain a phosphate ester dopant with the structure of Formula I; in Formula II, z, x, and y are all degrees of polymerization, and x+y is selected from integers between 1 and 10.

[0014]

[0015] In an embodiment of the present invention, the polymer represented by Formula II is obtained by polymerization of propylene oxide and carbon dioxide initiated by an initiator; the initiator is selected from one or more of monoethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether and pentaethylene glycol monomethyl ether.

[0016] In an embodiment of the present invention, the molar ratio of the initiator to propylene oxide is 1:1-10.

[0017] In embodiments of the present invention, the polymerization reaction is carried out in the presence of a catalyst; the catalyst comprises an oligoporphyrin aluminum catalyst.

[0018] In an embodiment of the present invention, the polymerization reaction is carried out at a temperature of 50–80°C for 35–40 h, and the carbon dioxide pressure is 5–6 MPa.

[0019] In an embodiment of the present invention, the phosphorylation reaction is carried out in an organic solvent. After the reaction is completed, a reaction solution is obtained, filtered, washed with water, and the organic solvent is removed. Then, organic extraction is performed, and the solid phase is taken to obtain the final product.

[0020] The present invention provides a polyaniline aqueous dispersion, which is formed by dispersing intrinsic polyaniline and a dopant in water, wherein the dopant is a phosphate ester dopant as described above.

[0021] In an embodiment of the present invention, the blending mass ratio of the dopant and intrinsic polyaniline is 2-10:1.

[0022] Compared with existing technologies, the phosphate ester dopant structure provided by this invention is shown in Formula I, which contains a hydrophilic ethylene glycol segment, a hydrophobic polycarbonate ether segment, and a phosphate ester structure, and introduces a low molecular weight ethylene glycol monomethyl ether structure into the molecule. This invention mainly utilizes the introduction of ester and ether bonds to successfully control the hydrophilicity of the dopant. When used for polyaniline dispersion, it can reduce the hydrophilicity of waterborne polyaniline, which is beneficial for the water processing and water resistance improvement of polyaniline.

[0023] Furthermore, the present invention utilizes hydrophilic polyethylene glycol monomethyl ether to initiate the polymerization of carbon dioxide and propylene oxide to prepare dopant precursors, and obtains the phosphate ester dopant through a simple phosphorylation reaction. The preparation method is simple and easy to implement. Attached Figure Description

[0024] Figure 1 This is the NMR characterization image of the dopant precursor in Example 1 of the present invention;

[0025] Figure 2 This is a DLS diagram of the dopant precursor in Embodiment 1 of the present invention;

[0026] Figure 3 This is the NMR characterization image of the phosphate ester dopant obtained in Example 1 of the present invention;

[0027] Figure 4 This is the GPC diagram of the phosphate ester dopant obtained in Example 1 of the present invention;

[0028] Figure 5 This is a DLS diagram of the phosphate ester dopant obtained in Example 1 of the present invention;

[0029] Figure 6 This is the GPC diagram of intrinsic polyaniline in Example 6 of the present invention;

[0030] Figure 7 This is a scanning electron microscope image of intrinsic polyaniline in Example 6 of the present invention;

[0031] Figure 8 This is a transmission electron microscope (TEM) image of the doped polyaniline in Example 6 of the present invention;

[0032] Figure 9 This is a dynamic light scattering result diagram of the polyaniline aqueous dispersion obtained in Example 6 of the present invention;

[0033] Figure 10 The UV-Vis spectra of the polyaniline aqueous dispersions obtained in Examples 6-8 of this invention are shown below.

[0034] Figure 11 This is a DLS diagram of the polymerization product in Comparative Example 2 of the present invention. Detailed Implementation

[0035] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] This invention provides a phosphate ester dopant for dispersing polyaniline, wherein the phosphate ester dopant has the structure of Formula I:

[0037]

[0038] Where z, m, and n are all aggregation degrees, and m+n is selected from integers between 1 and 10.

[0039] The use of phosphate ester dopants provided by this invention to disperse polyaniline can improve the water resistance of the aqueous dispersion, which is beneficial for its application.

[0040] The general structural formula of the phosphate ester dopant described in this invention embodiment is shown in Formula I, where z, m, and n are all degrees of polymerization, and the sum of m and n is an integer between 1 and 10, i.e., m + n = 1, 2, 3, 4, or 5, etc. The molecular structure of the phosphate ester dopant includes a hydrophilic segment of ethylene glycol, a hydrophobic polycarbonate ether segment, and a phosphate ester structure, as well as a low molecular weight ethylene glycol monomethyl ether structure. Moreover, this overall macromolecular chain structure can have one or two phosphate hydroxyl groups, and the corresponding number of phosphate hydroxyl groups can be two or one.

[0041] Some embodiments of the present invention describe phosphate ester dopants having a structure of formula I-1, or other embodiments have a structure of formula I-2;

[0042]

[0043]

[0044] The phosphate ester dopant described in this embodiment of the invention has a molecular weight of 200-1100. It does not exist in water as a solution, but rather agglomerates to form nanomicelles with a particle size in the range of 100-1000 nm (this can be analyzed by dynamic light scattering DLS in this embodiment of the invention).

[0045] In embodiments of the present invention, the phosphate ester dopant used for polyaniline dispersion has a hydrophilic ethylene glycol segment, which is beneficial for the hydroprocessing of polyaniline; simultaneously, the hydrophobicity of the polycarbonate ether segment reduces the hydrophilicity of the dopant, thereby reducing the hydrophilicity of polyaniline; a low molecular weight ethylene glycol monomethyl ether structure is also introduced into the molecule to further regulate the hydrophilicity of the dopant. Furthermore, the phosphate ester dopant uses the linked phosphate group as the active site for doping polyaniline, resulting in superior doping performance; by introducing the above-mentioned ester and ether bonds to regulate the hydrophilicity of the dopant, it is beneficial for the hydroprocessing and water resistance of polyaniline.

[0046] This invention provides a method for preparing phosphate ester dopants as described above, comprising:

[0047] The polymer shown in Formula II is phosphorylated with phosphorus pentoxide to obtain a phosphate ester dopant with the structure of Formula I; in Formula II, z, x, and y are all degrees of polymerization, and x+y is selected from integers between 1 and 10.

[0048]

[0049] The polymer represented by Formula II in this invention is a dopant precursor. The repeating structural units include hydrophilic ethylene glycol segments, hydrophobic polycarbonate ether segments, and a small amount of ethylene glycol monomethyl ether structures. In Formula II, z, x, and y represent the degree of polymerization, where x+y is 1, 2, 3, 4, or 5. In a preferred embodiment of this invention, this dopant precursor is prepared by initiating the polymerization of carbon dioxide and propylene oxide using hydrophilic polyethylene glycol monomethyl ether.

[0050] In a specific embodiment of the present invention, propylene oxide, an initiator, and a catalyst system are added to a reactor, and carbon dioxide gas is introduced to carry out the polymerization reaction. The initiator, also known as a chain transfer agent (CTA), is selected from one or more of ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, and pentaethylene glycol monomethyl ether, preferably triethylene glycol monomethyl ether. Furthermore, the molar ratio of the initiator to the propylene oxide monomer is preferably 1:1-10, more preferably 1:2-5. For the synthesis of the dopant precursor, embodiments of the present invention can control the initiator molecular weight to be 76-252, and the initiator / monomer feed ratio to be 1 / 2-1 / 10 to synthesize a dopant precursor with a molecular weight of 130-1000.

[0051] The low molecular weight dopant precursor described in the preferred embodiment of this invention is prepared by polymerization catalyzed by an oligoporphyrin aluminum catalyst. The oligoporphyrin aluminum catalyst is called an Oligo-Al catalyst, with the following structural formula, where n is 6-12 and is not related to n in the dopant structural formula.

[0052]

[0053] In a preferred embodiment of the present invention, bis(triphenylphosphine)ammonium chloride is used as an auxiliary catalyst component (hereinafter referred to as the co-catalyst). Other co-catalysts include Bu4NCl and Et4NBr, but bis(triphenylphosphine)ammonium chloride (PPNCl) exhibits higher activity. Based on the number of aluminum centers, the amount of oligoporphyrin aluminum catalyst (main catalyst) is 1 / 16000 of the amount of propylene oxide, and the molar ratio of the amount of co-catalyst to the number of aluminum centers in the main catalyst is 1:1. The core key of this embodiment lies in introducing carbon dioxide and propylene oxide into the hydrophilic polyethylene glycol segments through a polymerization reaction, thereby controlling the hydrophilicity of the dopant. In some embodiments, the polymerization reaction temperature is preferably 50–80°C, more preferably 60°C; the reaction time is preferably 35–40 h, more preferably 36 h; and the carbon dioxide pressure is 5–6 MPa. After the reaction in this embodiment of the invention is completed, the catalyst can be dissolved in hydrochloric acid-methanol solution, concentrated, and then removed with 200-300 mesh silica gel. The resulting colorless and transparent liquid is the dopant precursor with the structure of Formula II. For example, the polymerization reaction formula is as follows:

[0054]

[0055] In this embodiment of the invention, the polymer product shown in Formula II and organic solvents such as chloroform are added to a reactor, stirred and dissolved, preferably phosphorus pentoxide is added in batches, and the temperature is slowly increased to carry out the phosphorylation reaction. The reaction endpoint is determined by thin-layer chromatography. In this embodiment of the invention, the phosphate ester dopant is obtained through a simple phosphorylation reaction.

[0056] In embodiments of the present invention, the phosphorylation reaction temperature can be 50–60°C, and the time can be 6–8 h. After the reaction, the present invention preferably filters the obtained reaction solution with filter paper, adds a certain amount of water for washing (generally deionized water is used in experiments), and stirs for 1 h; removes the organic solvent chloroform by rotary evaporation at 50°C, decolorizes with activated carbon, and finally preferably extracts three times with chloroform at 5 times the volume of water. After collecting the organic phase and removing the solvent, the resulting pale yellow product is the phosphate ester dopant represented by Formula I. The phosphorylation reaction formula of the embodiments of the present invention is shown below:

[0057]

[0058] This invention provides a polyaniline aqueous dispersion, which is formed by dispersing intrinsic polyaniline and a dopant in water, wherein the dopant is the phosphate ester dopant described above. In an embodiment of this invention, intrinsic polyaniline and the phosphate ester dopant described above are mixed in water, preferably ultrasonicated every 12 hours, and stirred at room temperature for 95-98 hours to obtain the polyaniline aqueous dispersion.

[0059] The intrinsic polyaniline has a weight-average molecular weight of 55,000-56,000, specifically 55,200, with a molecular weight distribution of 4.40. Preferably, the blending mass ratio of the dopant to the intrinsic polyaniline is 2-10:1, and can be further adjusted to 2-5:1, for example, 2:1, 3:1, 4:1, etc. The ultrasonication and stirring are conventional dispersion methods, and the room temperature is generally 10-30°C; there are no special limitations in this invention.

[0060] The doping process involved in the embodiments of the present invention is shown in the following formula:

[0061]

[0062] Through testing and analysis, it was found that the polyaniline in the aqueous dispersion provided in this embodiment of the invention is in a good doping state, which is beneficial for application.

[0063] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. Unless otherwise specified, the raw materials used in the embodiments of this invention are all commercially available.

[0064] Example 1

[0065] 10 mL of propylene oxide, 10 mL of triethylene glycol monomethyl ether (initiator / monomer feed ratio of 1 / 2), 8.7 mg of Oligo-Al catalyst, and 5.1 mg of bis(triphenylphosphine)ammonium chloride were added to a 50 mL reactor. The carbon dioxide pressure was 5 MPa, and the reaction was carried out at 60 °C for 36 h. After the reaction was completed, the catalyst was dissolved in hydrochloric acid methanol solution, concentrated, and then removed with 200-300 mesh silica gel to obtain 20 g of colorless and transparent liquid, which is the dopant precursor.

[0066] The NMR characterization of the dopant precursor is shown in [link to NMR characterization]. Figure 1 ; Figure 2 Its DLS characterization results. For example... Figure 2 Characterization showed that the obtained dopant precursor formed nanomicelles in water.

[0067] 60 g of the obtained colorless and transparent liquid product and 300 mL of chloroform were added to a 500 mL round-bottom flask and stirred to dissolve. 21.3 g of phosphorus pentoxide was added in portions, and the mixture was slowly heated to 50 °C and reacted for 6 h. The reaction endpoint was determined by thin-layer chromatography. The reaction solution was filtered through filter paper, and 30 mL of deionized water was added. The mixture was stirred for 1 h. Chloroform was removed by rotary evaporation at 50 °C, and the product was decolorized with activated carbon. The mixture was extracted three times with chloroform at 5 times its volume of water. After removing the solvent from the organic phase, 58 g of a pale yellow product was obtained, denoted as P-PPC.

[0068] Figure 3 This is the P-PPC NMR characterization image. Figure 4 Its GPC characterization diagram. Figure 5The DLS diagram of the obtained phosphate ester dopants is shown below. Figure 5 As shown, the obtained phosphate ester dopants aggregate in water to form nanomicelles, rather than existing in solution.

[0069] Example 2

[0070] Diethylene glycol monomethyl ether was used as the initiator, with an addition amount of 7.34 mL. Other operations were the same as in Example 1.

[0071] Example 3

[0072] Tetraethylene glycol monomethyl ether was used as the initiator, with an addition amount of 12.45 mL. Other operations were the same as in Example 1.

[0073] Example 4

[0074] When the initiator / monomer ratio is 1:3, the amount of propylene oxide added is 10 mL, the amount of triethylene glycol monomethyl ether added is 6.7 mL, and other operations are the same as in Example 1.

[0075] Example 5

[0076] When the initiator / monomer ratio is 1:4, the amount of propylene oxide added is 10 mL, the amount of triethylene glycol monomethyl ether added is 5 mL, and other operations are the same as in Example 1.

[0077] The above embodiments control the molecular weight of the initiator and the initiator / monomer feed ratio to synthesize dopant precursors with a molecular weight of 130-1000, and further synthesize phosphate ester dopants.

[0078] Examples 6-8

[0079] Take 0.1g of intrinsic polyaniline (denoted as PANI), and 0.2g, 0.3g, and 0.4g of the pale yellow products obtained in Example 1, respectively. Mix them in 10mL of water, sonicate for 10min every 12h, and stir at room temperature for 96h to obtain polyaniline aqueous dispersions.

[0080] In Example 6, m P-PPC / m PANI =4 / 1; In Example 7, m P-PPC / m PANI =3 / 1; In Example 8, m P-PPC / m PANI =2 / 1.

[0081] For the GPC characterization of intrinsic polyaniline, see [link to GPC characterization]. Figure 6 (Weight-average molecular weight is 55,200, molecular weight distribution is 4.40); its scanning electron microscope image is as follows. Figure 7 As shown, the transmission electron microscope image of doped polyaniline is as follows: Figure 8As shown in the figure, transmission electron microscopy reveals that polyaniline exists in the aqueous dispersion as nanowires.

[0082] Figure 9 The image shows the dynamic light scattering results of the polyaniline aqueous dispersion obtained in Example 6. It can be seen that polyaniline is dispersed in water at a size of about 800 nm.

[0083] Figure 10 The images show the UV-Vis spectra of the polyaniline aqueous dispersions obtained in Examples 6-8, including the UV-Vis spectral curves of intrinsic polyaniline and phosphate ester dopants; for example... Figure 10 As shown, the high absorption peak at 800-1000 nm indicates that the polyaniline segments in the aqueous dispersion exist in a relatively extended manner, and the polarization sub-peak at 420 nm indicates that the polyaniline is in a good doping state.

[0084] The introduction of carbonate bonds and propylene oxide in this dopant reduces the water solubility of the resulting PANI / P-PPC, while also significantly improving its water resistance after drying into a solid state; it did not break or dissolve even after being soaked in water for a week.

[0085] Comparative Example 1

[0086] Using ethanol as a chain transfer agent, the reaction formula is as follows: 5 mL of propylene oxide, 0.83 mL of ethanol, 5.4 mg of aluminum oligoporphyrin, and 3.2 mg of bis(triphenylphosphine)ammonium chloride were added to a 10 mL reaction vessel, and the reaction was carried out at 60 °C for 36 h. After the reaction, the product was dissolved in a hydrochloric acid-methanol solution, concentrated, and the catalyst was removed with 200-300 mesh silica gel to obtain a colorless and transparent product. Compared with the precursor product in Example 1, this product has poor hydrophilicity and cannot be dispersed in water.

[0087]

[0088] Comparative Example 2

[0089] Without introducing carbonate groups, the reaction formula is as follows: 2.5 mL of propylene oxide, 2.5 mL of triethylene glycol monomethyl ether, 2.2 mg of oligoporphyrin aluminum, and 1.3 mg of bis(triphenylphosphine)ammonium chloride were added to a 10 mL reactor, and the reaction was carried out at 60 °C under a nitrogen atmosphere for 36 h. After the reaction, the product was dissolved in hydrochloric acid-methanol solution, concentrated, and the catalyst was removed with 200-300 mesh silica gel to obtain a colorless and transparent product. This product is more hydrophilic than the precursor product in Example 1. See the DLS diagram below. Figure 11 The main peak particle size in the water was measured to be 78 nm.

[0090]

[0091] As can be seen from the above embodiments, the phosphate ester dopant structure provided by the present invention contains a hydrophilic ethylene glycol segment, a hydrophobic polycarbonate ether segment, and a phosphate ester structure, and introduces a low molecular weight ethylene glycol monomethyl ether structure into the molecule. The present invention mainly utilizes the introduction of ester and ether bonds to successfully control the hydrophilicity of the dopant. When used for polyaniline dispersion, it can reduce the hydrophilicity of waterborne polyaniline, which is beneficial to the water processing and water resistance improvement of polyaniline. Furthermore, the present invention uses hydrophilic polyethylene glycol monomethyl ether to initiate the polymerization of carbon dioxide and propylene oxide to prepare the dopant precursor, and obtains the phosphate ester dopant through a simple phosphorylation reaction. The preparation method is simple and easy to implement.

[0092] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be within the protection scope of the present invention.

Claims

1. A phosphate ester dopant for dispersing polyaniline, characterized in that, The phosphate ester dopant described has the structure of Formula I: Where z, m, and n are all aggregation degrees, and m+n is selected from integers between 1 and 10.

2. The phosphate ester dopant according to claim 1, characterized in that, The phosphate ester dopants described herein exist in the form of nanomicelles in water.

3. The method for preparing the phosphate ester dopant as described in claim 1 or 2, characterized in that, include: The polymer shown in Formula II is phosphorylated with phosphorus pentoxide to obtain a phosphate ester dopant with the structure of Formula I; in Formula II, z, x, and y are all degrees of polymerization, and x+y is selected from integers between 1 and 10.

4. The method for preparing the phosphate ester dopant according to claim 3, characterized in that, The polymer represented by Formula II is obtained by polymerization of propylene oxide and carbon dioxide using an initiator; the initiator is selected from one or more of monoethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether and pentaethylene glycol monomethyl ether.

5. The method for preparing the phosphate ester dopant according to claim 4, characterized in that, The molar ratio of the initiator to propylene oxide is 1:1-10.

6. The method for preparing the phosphate ester dopant according to claim 4, characterized in that, The polymerization reaction is carried out in the presence of a catalyst, which includes an oligoporphyrin aluminum catalyst.

7. The method for preparing the phosphate ester dopant according to claim 6, characterized in that, The polymerization reaction is carried out at a temperature of 50–80°C for 35–40 hours, and the carbon dioxide pressure is 5–6 MPa.

8. The method for preparing the phosphate ester dopant according to any one of claims 3-7, characterized in that, The phosphorylation reaction is carried out in an organic solvent. After the reaction is completed, the reaction solution is obtained, filtered, washed with water, and the organic solvent is removed. Then, organic extraction is performed, and the solid phase is collected to obtain the final product.

9. A polyaniline aqueous dispersion, characterized in that, It is formed by dispersing intrinsic polyaniline and a dopant in water, wherein the dopant is a phosphate ester dopant as described in claim 1 or 2.

10. The polyaniline aqueous dispersion according to claim 9, characterized in that, The mass ratio of the dopant to intrinsic polyaniline is 2-10:1.

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