Alkaline suspension system constructed from hydrotrope and amine

Abstract

A non-settling water-based pourable alkaline suspension may be prepared from a mixture of at least one water-soluble amphiphile and at least one oil-soluble amphiphile, wherein the amphiphile has 6 to 11 carbon atoms in the hydrophobic portion of the amphiphile. The water soluble amphiphile is classified as a hydrotrope, and the oil soluble amphiphile component contains at least one amine group.

Description

Field of the Invention

[0001] The present invention relates to an alkaline, structured, low-foaming amphiphilic suspending system for preparing suspensions of water-insoluble (or slightly water-soluble) solid particles or liquids. The present invention further relates to a composition comprising the suspending system. Background Art

[0002] A recent patent application (U.S. Provisional Application No. 63 / 308452) claims a novel structured low foaming composition that is extremely cost effective and capable of suspending immiscible solid or liquid particles without settling using a blend of short chain (i.e., 7 to 11 carbon atoms) amphiphiles in water. The system includes a mixture of at least one water-soluble amphiphile and at least one water-insoluble amphiphile, wherein the at least one water-soluble amphiphile is a hydrotrope. The hydrotrope is a high HLB hydrotrope having an HLB value of 10 or more, and the at least one water-insoluble amphiphile is a low HLB amphiphile having an HLB value of less than 10 and containing at least one hydroxyl group.

[0003] Without wishing to be bound by theory, it is believed that the hydroxyl groups provide hydrogen bonds that "cemented" the amphiphiles together to form regular nanometer-sized lamellar liquid crystal droplets. The regularly sized nanometer droplets have positively charged surfaces (although they are generally electrically neutral), and it is believed that the unequal charge distribution throughout the droplet causes the droplets to continually repel each other, resulting in a 3D structure with a yield point that allows solids, liquids, or gases to be suspended. The systems have high optical clarity and have a pronounced yield point, as evidenced by the fact that they are able to suspend gas bubbles.

[0004] It has now been discovered that structured suspension systems can be constructed from mixtures of short chain (i.e., C7-C11 carbon atoms) hydrotropes and amine-containing amphiphiles. Surprisingly, such suspension systems are shear thickening, in contrast to the shear thinning behavior of suspension systems formed from hydroxyl-containing, water-insoluble amphiphiles and hydrotropes. Summary of the invention

[0005] According to a first aspect of the present invention, there is provided an alkaline structured aqueous system having a yield point and capable of suspending solid, liquid or gaseous particles, wherein the system comprises a mixture of at least one water-soluble amphiphile and at least one water-insoluble amphiphile. The at least one water-soluble amphiphile is a hydrotrope and the at least one water-insoluble amphiphile contains at least one amine group. In a further aspect, the hydrotrope has at least one polar head group and a lipophilic moiety having less than 12 carbon atoms per polar head group. Most unexpectedly and surprisingly, it has been found that low-foaming, shear-thickening structured lamellar suspension systems comprising a high proportion of hydrotropes can be successfully formulated. The systems can have high optical clarity and have a significant yield point, as evidenced by the fact that they are capable of suspending gas bubbles.

[0006] The structured suspension system can be used to suspend non-water soluble materials such as graphene or diamond powder used in industrial applications where high foaming surfactants are not suitable. Therefore, another aspect of the present invention is a composition comprising an alkaline structuring system, comprising: (a) based on the weight of the structured aqueous system, 2 wt% to 50 wt% of a mixture of at least one water-soluble amphiphile and at least one water-insoluble amphiphile, wherein the at least one water-soluble amphiphile is a hydrotrope, the hydrotrope comprising at least one polar head group and a lipophilic tail group having 6 to 11 carbon atoms per polar head group, and the at least one water-insoluble amphiphile contains at least one amine group; (b) at least one of solid, liquid or gas particles suspended in the alkaline structuring system; and (c) making the composition to a total of 100% water. In some embodiments, the solid particles constitute from about 0.5 wt% to about 25 wt% of the composition. In some embodiments, the solid particles are graphene particles.

[0007] Another aspect of the present invention is a method for preparing a stable graphene dispersion comprising: (a) forming a basic structured aqueous system comprising water and 2 wt % to 50 wt % of a mixture of at least one water-soluble amphiphile and at least one water-insoluble amphiphile, based on the weight of the structured aqueous system, wherein the at least one water-soluble amphiphile is a hydrotrope comprising at least one polar head group and a lipophilic tail group having 6 to 11 carbon atoms per polar head group, and the at least one water-insoluble amphiphile contains at least one amine group; and (b) suspending graphene particles in the structured aqueous system to form a stable graphene dispersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Shown are the chemical structures of exemplary low HLB amphiphiles useful in the present invention.

[0009] Figure 2 Shown are the chemical structures of exemplary high HLB hydrotropes useful in the present invention. DETAILED DESCRIPTION

[0010] The present invention relates to an alkaline suspension system based on a lamellar mesophase, which is constructed by amphiphilic molecules. It has a high optical transparency, is low foaming and can be extremely low in electrolyte. Systems with a high optical transparency typically have a transmittance percentage greater than about 50 using a 1 cm cuvette at a wavelength of 570 nanometers, where the composition is measured at 25°C without dyes and sunscreens. "Low foaming (foaming)" means that any foam generated during the processing of forming the suspension system is short-lived and collapses within a few seconds. Systems that are extremely low in electrolyte are systems with less than 2% by weight, preferably less than 1% by weight of electrolyte. For example, the structured suspension system may be electrolyte-free. The alkaline suspension system of the present technology is also shear-thickening, showing an increase in viscosity over time when shaken or sheared. Once shearing is stopped, the alkaline suspension system will return to the initial viscosity over time (usually within 24 hours). As a suspension medium for payloads such as pesticides, pigments, graphene, oils, etc., the suspension system has a wide range of applications.

[0011] The amphiphilic molecules used to prepare the suspension system include at least one water-insoluble amphiphile containing an amino group and at least one water-soluble amphiphile as a hydrotrope. A hydrotrope is a molecule having a hydrophilic or polar head group and a hydrophobic (lipophilic) tail group, but the tail group is generally too small to cause spontaneous self-association or aggregation in aqueous solution. The specific combination of water-insoluble amine-containing amphiphile and hydrotrope can form a shear-thickening structured system that has a yield point and is able to suspend solid particles, liquid droplets and gas bubbles.

[0012] The amphiphiles used to prepare the structured suspension system should include at least one amphiphile with a low (e.g., less than 10) hydrophilic-lipophilic balance (HLB), and at least one amphiphile with a high (e.g., 10 or higher) HLB. The total HLB of the mixture should be in the range of liquid crystal formation, which can be about 11 to 13, preferably about 12 HLB units.

[0013] Low HLB amphiphiles include a lipophilic tail group containing less than 12 carbon atoms and at least one amine group. In some embodiments, low HLB amphiphiles may include at least one lipophilic tail, the lipophilic tail including 4 to 11 carbon atoms, alternatively 5 to 11 carbon atoms, alternatively 6 to 11 carbon atoms, alternatively 7 to 11 carbon atoms. The lipophilic tail group may be linear or branched.

[0014] In some embodiments, the low HLB amphiphile may include at least one linear tail having a carbon chain comprising 4, 5, 6, 7, 8, 9 or 10 carbon atoms. In other embodiments, the low HLB amphiphile may have a branched or cyclic (including aromatic) tail with 6, 7, 8, 9 or 10 carbon atoms. Without wishing to be bound by theory, it is believed that the amine groups of the low HLB amphiphile exchange protons with the head groups of the hydrotropes. This is believed to be the driving force for the formation of nanodroplets and is the "binder" that holds the droplets together. Examples of suitable water-insoluble amphiphiles for forming the suspension system include, but are not limited to, octylamine, p-ethylaniline, p-toluidine and 4-isopropylaniline.

[0015] It is also possible to produce mixed hydrogen bonding (amino plus hydroxyl) systems. In fact, these mixed systems may be preferred for some applications, as pure amino hydrogen bonding has been found to impart shear thickening behavior in structured systems. This is believed to be due to the amino groups providing droplet-droplet hydrogen bonding, and the associated droplet clusters causing thickening under applied shear forces.

[0016] High HLB amphiphiles or hydrotropes include at least one polar head group and at least one lipophilic tail. The lipophilic tail can be aliphatic or aromatic. The hydrotrope can have a lipophilic tail, which includes at least 5, alternatively about 6, about 7, about 8, about 9, about 10 or about 11 carbon atoms. In some embodiments, the lipophilic tail is a linear lipophilic tail. In embodiments including a linear lipophilic tail, the carbochain can include 5 carbon atoms, alternatively about 6, about 7, about 8, about 9, about 10 or about 11 carbon atoms. In some embodiments, the lipophilic tail is a cyclic or branched tail. For 6 carbon cyclic (including aromatic) tails, the tail should have at least one side (hanging) methyl. Alkylbenzene sulfonates containing 6 or more carbon atoms in the alkyl portion are not considered as hydrotropes defined herein. Polar groups may include sulfate, sulfonate, carboxylate or phosphate groups.The counterion for the polar head group may be sodium, potassium, lithium, monoethanolamine, diethanolamine or triethanolamine.

[0017] In some embodiments, the high HLB amphiphile may have two or dual polar head groups. For example, it is believed that sulfonated oleic acid may function as a high HLB component in the structured aqueous system. Without being bound by theory, this may be due to those molecules in the mixture that have been sulfonated at the double bond to produce a short-tailed, dual-headed hydrotrope. These molecules are believed to bunch and fold in the vesicle so that about 10 carbon atoms are incorporated into the lipophilic portion of the bilayer.

[0018] Di(C4-C18)alkyl phosphates can also function as hydrotropes in structured aqueous systems.

[0019] For hydrotropes with single and cyclic tails, the total number of carbon atoms may be between 7 and 11. It is believed that a tail comprising 7-11 carbon atoms produces sufficient lipophilic properties to allow the tail to associate into a liquid crystal bilayer. For hydrotropes with a dual head group, the number of carbon atoms may be 7-11 carbon atoms relative to each polar head group. Examples of hydrotropes that can be used in the present invention are triethanolamine octanoate, ethanolamine octanoate, sodium octyl sulfate, sodium cumene sulfonate, sodium xylene sulfonate, sodium toluene sulfonate, sulfonated oleic acid, ammonium octyl sulfate, triethanolamine octyl sulfate, and octylamine hydrochloride.

[0020] Experiments have shown that for linear tails, a minimum chain length of about 7-8 carbon atoms is preferred in order to form liquid crystals. Amphiphiles with shorter chain lengths than this may be too soluble. The preferred short chain lengths of the lipophilic tails of the amphiphiles, i.e., about 7 to 10 carbon atoms, are believed to form extremely flexible narrow double layers, and this flexibility allows them to be packed into microvesicles containing only a small number (e.g., 5) of concentric shells. It is believed that these microvesicles are nanodroplets of lamellar phases with positively charged surfaces, although they are generally electrically neutral. Without being bound by theory, it is believed that the unequal charge distribution throughout the droplet causes the droplets to constantly repel each other, resulting in a 3D structure with a yield point that allows solids, liquids, or gases to be suspended.

[0021] Linear amphiphiles with longer chains (i.e., 12 carbon atoms and above) give thicker bilayers that are more rigid and tend to pack into large multilamellar vesicles with dozens of concentric shells. The large vesicles are of such a size that they reflect light rather than transmit it, with the result that these particular systems are opaque.

[0022] Figure 1 Examples of low HLB (water insoluble) amphiphiles of the present invention that have been found to be effective for forming the structured alkaline suspending system are provided. Figure 2 Examples of high HLB (water soluble) amphiphiles of the present invention that have been found to be effective for forming the structured alkaline system are provided. Figure 1 Any combination of low HLB amphiphiles in Figure 2 Any combination of high HLB amphiphiles (hydrotropes) in the formula (1) are blended together to produce an alkaline structured aqueous system, provided that the combination of low HLB amphiphiles includes at least one amphiphile containing an amine group. The alkaline structured aqueous system formed by the combination of low HLB amphiphiles and high HLB amphiphiles has a high degree of clarity and is capable of suspending solids. However, Figure 1 and Figure 2The amphiphiles shown are not intended to be an exhaustive list of examples of the invention.

[0023] The at least one water-soluble amphiphile and the at least one water-insoluble amphiphile are mixed together in water to obtain the structured aqueous system. The active components of the suspension system (i.e., the hydrotrope and the at least one water-insoluble amphiphile) may be present in a total amount of about 2 to about 50% w / w (weight / weight), about 4 to about 45% w / w, about 6 to about 40% w / w, about 8 to about 35% w / w, about 10 to about 30% w / w, or about 15 to about 25% w / w, based on the total weight of the structured aqueous system.

[0024] The hydrotrope and the at least one water-insoluble amphiphile may be present in a total amount of at least about 2% w / w, about 4% w / w, about 6% w / w, about 8% w / w, about 10% w / w, about 12% w / w, about 14% w / w, about 16% w / w, about 18% w / w, about 20% w / w, about 22% w / w, about 24% w / w, about 26% w / w, about 28% w / w, about 30% w / w, about 35% w / w, about 40% w / w, about 45% w / w, or at least about 50% w / w, based on the total weight of the structured aqueous system.

[0025] In some embodiments, the concentration of the amphiphile may need to be 10 wt% or higher in order to "fill" the available volume and provide a yield point. However, adding components that can increase the repulsion of the nanodroplets to the structured aqueous system can provide a yield point at active concentrations below 10%. Components that can increase the repulsion between nanodroplets include morpholine soaps, C8 / C10 alkylamine oxides, 1,4-thiazine, thiomorpholine, and thiomorpholine 1,1 dioxide.

[0026] The ratio of hydrotropes to water-insoluble amphiphiles is at least partially determined by the specific hydrotropes and water-insoluble amphiphiles that form the structured system. Suitable suspension systems including high and low HLB amphiphiles and the optimal ratios of specific ingredients can be determined experimentally. Various ratios of hydrotropes and water-insoluble amphiphiles are pre-blended together, then diluted with water to a total active concentration of about 15% by weight and mixed (manual low shear mixing). These compositions thicken and remain substantially transparent during mixing, and then air is shaken into them. Identify isotropic compositions that suspend bubbles, and then evaluate them as "strong" or "weak" (high or low yield point) depending on whether the system suspends large or small bubbles. In a series of samples prepared with different ratios of high HLB amphiphiles to low HLB amphiphiles, several samples usually show suspension properties. A series of mid-range samples tend to show the highest yield point, that is, suspend the largest bubbles, so the center of the mid-range is identified as the optimal ratio for microvesicle formation. Generally, suitable weight ratios of water-insoluble amphiphile to hydrotrope may range from 1:1 to about 4:1.

[0027] The structured aqueous system is prepared by low shear mixing each of the constituent components together at room temperature or above (above) room temperature, for example, about 27, about 28, about 29, about 30, about 32, about 34, or about 35° C. Mixing is applied until the blend thickens and reaches a yield point, at which time the blend becomes able to suspend insoluble (solid, liquid or gas) particles. The amphiphiles are usually (but not necessarily) pre-blended together before being dispersed in water. This has the advantage of preventing any undesirable emulsification from occurring. Pre-blending the amphiphiles also has the following additional benefits: a commercially available concentrate is prepared to be sold to customers who prefer to make the finished structured liquid formulation "in-house". The high-active concentrate is still pourable and is easily dispersed by low shear mixing at room temperature to form a structured aqueous system. Although shear thickening, the resulting structured aqueous system has a sufficiently low viscosity so that it is flowable and has good suspension capabilities without the addition of electrolytes (i.e., it can be electrolyte-free). In some embodiments, the structured aqueous system is clear or slightly turbid.

[0028] The structured aqueous system can be stable at temperatures ranging from 0 to 60° C., with some of these systems being stable even at lower or higher temperatures. The structured aqueous system is a low foaming system that can be used to suspend a variety of solid, liquid or gas particles, and is particularly useful in applications where foaming is not desired, or where a surfactant system cannot be used due to interaction with a dispersant material. Since the structured system is alkaline, it is useful for suspending acidic materials, or can be used in applications where acidic systems are not suitable or where pH control is required. The shear thickening behavior of the structured alkaline system can make such a system useful for preventing sedimentation of suspended solids, for example during transportation. Materials suspended in a shear thinning system may have a tendency to settle due to movement during transportation. Due to the shear thickening behavior of the alkaline structured system, the structured alkaline system of the present technology may be able to better keep materials suspended.

[0029] The particulate solids that can be suspended in the present structured aqueous system include, but are not limited to, graphene, diamond powder, pesticides and herbicides, and pigments. The amount of particulate solids that can be suspended in the present structured aqueous system can range from about 0.5% to about 25% by weight of the structured aqueous system. The structured aqueous system can be used in many different applications, such as preparing graphene dispersions, diamond suspensions (slurries), oil-free lubricants, cutting fluids, agricultural compositions such as pesticide, herbicide and / or fertilizer suspensions, pigment suspensions, adhesive suspensions, 3D printing media, and ink suspensions.

[0030] In some embodiments, the alkaline structured aqueous system can be used to suspend graphene particles. Therefore, one aspect of the present technology is a method for preparing a stable graphene dispersion. The graphene dispersion can be prepared as follows: forming an alkaline structured aqueous system, which includes water and a mixture of 2% to 50% by weight of at least one water-soluble amphiphile and at least one water-insoluble amphiphile containing at least one amine group, based on the weight of the structured aqueous system, wherein the at least one water-soluble amphiphile is a hydrotrope, the hydrotrope including at least one polar head group and a lipophilic tail group having 6 to 11 carbon atoms relative to each polar head group; and suspending the graphene particles in the structured aqueous system to form a stable graphene dispersion. In some embodiments, the graphene particles can be mixed with the hydrotrope and water to form a uniform mixture, and then a low HLB, water-insoluble amphiphile can be added to the mixture to form a structured aqueous system, wherein the graphene particles are stably dispersed in the structured aqueous system. Alternatively, the low HLB, water-insoluble amphiphile and hydrotrope may be mixed together to form the alkaline structured aqueous system, and the graphene particles may be mixed with the structured aqueous system to form a stable graphene dispersion. In some embodiments, the low HLB amphiphile and the hydrotrope may be pre-blended to form a concentrate, which is then diluted to form the structured aqueous system. The graphene particles may be mixed with the concentrate prior to dilution.

[0031] Example

[0032] The following examples describe some preferred embodiments of the present technology, but the present technology is not limited thereto. Other embodiments include, but are not limited to, those described in the above written description, including additional or alternative components, alternative concentrations, and additional or alternative properties and uses.

[0033] Example 1

[0034] A 3:1 w / w blend of octylamine:octylamine hydrochloride was prepared at 11.0 wt% total active by adding octylamine to a hydrochloric acid solution at room temperature and gently stirring the mixture by hand. The resulting sample had a slightly turbid and viscosity of approximately 2000 cp at room temperature. It had a strong yield point (as evidenced by its suspended large bubbles) and was found to thicken upon stirring. When stirring was stopped, the viscosity was found to have dropped to the initial value.

[0035] Example 2

[0036] A 1:1.6 w / w blend of sulfonated oleic acid:octylamine was prepared at 11.6 wt% total actives by adding octylamine to the sulfonated oleic acid solution at room temperature and gently stirring the mixture by hand. The resulting sample had a slightly turbid and viscosity of approximately 1500 cp at room temperature. It had a strong yield point (as evidenced by its suspended large bubbles) and was found to thicken upon stirring. When stirring was stopped, the viscosity was found to have dropped to the initial value.

[0037] Example 3

[0038] A 1:1 w / w blend of sodium cumene sulfonate:octylamine was prepared at 20.0 wt% total active by adding octylamine to a sodium cumene sulfonate solution at room temperature and gently stirring the mixture by hand. The resulting sample was turbid and had a viscosity of approximately 1500 cp at room temperature. It had a strong yield point (as evidenced by its suspension of a large number of bubbles) and was found to thicken upon stirring. When stirring was stopped, the viscosity was found to decrease to the initial value.

[0039] Example 4

[0040] A structured system for suspending graphene was prepared from a 3:1 w / w blend of octylamine:octylamine hydrochloride at 4 wt% total actives. Even with only 4% total actives, this system was able to suspend 20% w / w of 100% graphene powder (PUREGRAPH 50 from First Graphene).

[0041] The present technology is now described in such sufficient, clear and concise terms as to enable those skilled in the art to practice the technology. It should be understood that the foregoing describes preferred embodiments of the present technology and that modifications may be made therein without departing from the spirit or scope of the present technology as set forth in the appended claims. Furthermore, the embodiments provided are not exhaustive but illustrate several embodiments that fall within the scope of the claims.

Claims

1. An alkaline structured aqueous system having a yield point and capable of suspending solid, liquid or gaseous particles, the structured aqueous system comprising: (a) from 2% to 50% by weight, based on the weight of the structured aqueous system, of a mixture of at least one water-soluble amphiphile and at least one water-insoluble amphiphile containing at least one amine group, wherein the at least one water-soluble amphiphile is a hydrotrope comprising at least one polar head group and a lipophilic tail group having from 6 to 11 carbon atoms per polar head group, and (b) bringing the structured aqueous system to a total of 100% water.

2. The structured aqueous system of claim 1, wherein the at least one water-soluble amphiphile and the at least one water-insoluble amphiphile are present in a total amount of 10% to 30% by weight of the structured aqueous system.

3. The structured aqueous system of claim 1 or 2, wherein the water-insoluble amphiphile has a hydrophobic tail portion containing 6 to 11 carbon atoms.

4. The structured aqueous system of any one of claims 1 to 3, wherein the hydrotrope is selected from sodium toluene sulfonate, sodium xylene sulfonate, sodium cumene sulfonate, sodium octyl sulfate, triethanolamine caprylate, ethanolamine caprylate, sulfonated oleic acid, octylamine hydrochloride, ammonium octyl sulfate, triethanolamine octyl sulfate, and di-(C4-C18)-alkyl phosphates.

5. The structured aqueous system of any one of claims 1 to 4, wherein the water-insoluble amphiphile is selected from octylamine, p-ethylaniline, isopropylaniline and p-toluidine.

6. The structured aqueous system of any one of claims 1 to 5, wherein the weight ratio of the water-insoluble amphiphile to the hydrotrope is in the range of 1:1 to 4:

1.

7. The structured aqueous system of any one of claims 1-6, wherein the structured aqueous system has an overall HLB value in the range of about 11 to about 13.

8. The structured aqueous system according to any one of claims 1 to 7, wherein the structured aqueous system further comprises solid particles, liquid droplets or gas bubbles stably suspended in the structured aqueous system.

9. The structured aqueous system of claim 8, wherein the solid particles are graphene.

10. The structured aqueous system of claim 8 or 9, wherein the solid particles comprise up to 25% by weight of the structured aqueous system.

11. A composition comprising: (a) a structured aqueous system comprising: from 2% to 50% by weight, based on the weight of the structured aqueous system, of a mixture of at least one water-soluble amphiphile and at least one water-insoluble amphiphile containing at least one amine group, wherein the at least one water-soluble amphiphile is a hydrotrope comprising at least one polar head group and a lipophilic tail group having from 6 to 11 carbon atoms per polar head group; (b) at least one solid, liquid or gas particle suspended in said structured aqueous system; and (c) bringing the composition to a total of 100% water.

12. The composition of claim 11 wherein the at least one water soluble amphiphile and the at least one water insoluble amphiphile are present in a total amount of 10% to 30% by weight of the structured aqueous system.

13. A composition as claimed in claim 11 or 12, wherein the water-insoluble amphiphile has a hydrophobic tail portion containing 6 to 11 carbon atoms.

14. A composition as claimed in any one of claims 11 to 13, wherein the hydrotrope is selected from sodium toluene sulfonate, sodium xylene sulfonate, sodium cumene sulfonate, sodium octyl sulfate, triethanolamine octanoate, ethanolamine octanoate, sulfonated oleic acid, octylamine hydrochloride, ammonium octyl sulfate, triethanolamine octyl sulfate, and di-(C4-C18)-alkyl phosphates.

15. The composition of any one of claims 11 to 14, wherein the water-insoluble amphiphile is selected from octylamine, p-ethylaniline, isopropylaniline, and p-toluidine.

16. The composition of any one of claims 11-15, wherein the solid particles suspended in the structured aqueous system comprise from 0.5% to 25% by weight of the structured aqueous system.

17. The composition of claim 16, wherein the solid particles suspended in the structured aqueous system are graphene particles.

18. A method for preparing a stable graphene dispersion, comprising: (a) forming an alkaline structured aqueous system comprising: water and from 2% to 50% by weight, based on the weight of the structured aqueous system, of a mixture of at least one water-soluble amphiphile and at least one water-insoluble amphiphile containing at least one amine group, wherein the at least one water-soluble amphiphile is a hydrotrope comprising at least one polar head group and a lipophilic tail group having from 6 to 11 carbon atoms per polar head group; and (b) suspending graphene particles in the alkaline structured aqueous system to form a stable graphene dispersion.

19. The method of claim 18, wherein the graphene dispersion comprises up to 25 wt% graphene particles.

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