Description:BACKGROUND

FIELD OF THE DISCLOSURE
Various embodiments of the disclosure relate generally to interpenetrating polymer network comprising liquid crystalline graphene-based material. More specifically, various embodiments of the disclosure relate to methods of preparing graphene-based liquid crystalline interpenetrating polymer network; films and membranes comprising the graphene-based liquid crystalline interpenetrating polymer network.

DESCRIPTION OF THE RELATED ART
Membrane technology is a viable solution for molecular sieving or separation of unwanted ions or molecules from a solution. It is widely used across industries such as water treatment, food, beverage, and pharmaceutical industry. With depleting sources of water, membrane technology has opened up avenues to enhance the quality of water from non-traditional sources such as wastewater, brackish water, and seawater.
Most commonly used membranes are polymeric, composed of cellulose acetate, polyamide, polyimide, polysulfone, or polyethersulfone. Although pore size of the membrane plays a significant role in membrane selectivity by size exclusion of contaminants, charge on the membrane is also an important factor. Polymeric membranes contain ionizable groups such as carboxylic or sulfonic acid groups, resulting in surface charges in presence of feed solution. Membranes have demonstrated capabilities in removing colloidal contaminants, persistent organic compounds, pathogenic microorganisms, viruses, salts, ions, and heavy metals from water. However, existing commercially available polymeric membranes suffer from major drawbacks such as scaling, cake formation, and biofouling. Some of these drawbacks have been addressed by addition of anti-caking agents and anti-scaling agents, however, biofouling remains a key challenge in membrane technology.
Interpenetrating polymer networks (IPNs) are a class of polymer materials comprising two or more polymeric systems that are self-cross-linked and interlaced at the molecular level. The simultaneous presence of two or more distinct polymeric systems in IPNs can lead to enhanced chemical resistance and thermal stability when compared to a single-component polymeric system. Membranes comprising IPN may offer a versatile platform for designing filtration systems with tailored properties and enhanced performance, making them promising candidates for various membrane technology applications.
Graphene oxide (GO) has emerged as a promising material for various applications, including filtration membranes. GO membranes can selectively separate molecules based on size, charge, and through interactions of contaminants with functional groups on the membrane surface. However, GO membranes are mechanically fragile and prone to damage or delamination under mechanical stresses or pressure gradients. To overcome some of these challenges, GO can be combined with other materials to create composite membranes with enhanced properties. For example, incorporating GO into polymer matrices can improve mechanical strength. While GO membranes exhibit high selectivity, their permeability may be lower compared to other filtration membranes. The lower permeability can affect the throughput and efficiency of filtration, in particular for applications requiring high flux rates. Moreover, fabrication of GO membranes often involves complex and time-consuming processes, and hence achieving uniformity and reproducibility in membrane fabrication can be challenging, leading to variations in membrane performance.
Hence, there is a need to optimize the performance, scalability, and cost-effectiveness of graphene-based membrane technology and provide solutions for application-specific filtration systems.
Limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of described systems with some aspects of the present disclosure, as set forth in the remainder of the present application and with reference to the drawings.

SUMMARY

According to the embodiments of the present disclosure, a liquid crystalline film comprising an interpenetrating polymer network (IPN) is provided. The interpenetrating polymer network comprises a first polymer network comprising a first polymer. The first polymer comprises polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), poly(butylene succinate-co-adipate) (PBSA), polyethersulfone (PES), or combinations thereof. The IPN further comprises a second polymer network comprising a second polymer. The second polymer comprises polydopamine, poly(methacryloyloxylethyl phosphorylcholine) (polyMPC), poly(sulfobetaine methacrylate) (polySBMA), poly(sulfobetaineacrylamide) (polySBAAm), carboxybetaine, sulfobetaine, or combinations thereof. The IPN further comprises a graphene material, wherein the graphene material is liquid crystalline. The graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.
In one embodiment, a filtration system comprising the liquid crystalline film is provided. The liquid crystalline film functions as a membrane. The membrane is support-free.
In another embodiment, a method of forming a liquid crystalline film comprising an interpenetrating polymer network is provided. The method comprises providing a first mixture, wherein the first mixture comprises a first polymer, and one of a second monomer or a second polymer. The method further comprises providing a dispersion comprising a graphene material into the first mixture under agitation at a temperature in a range of 60 °C to 80 °C to form a homogenous mixture. The method further comprises casting the homogeneous mixture to form a layer over a substrate. The method further comprises immersing the substrate comprising the layer in a coagulating bath to obtain the liquid crystalline film, wherein the film comprises the interpenetrating polymer network. The interpenetrating polymer network comprises a first polymer network comprising the first polymer, a second polymer network comprising the second polymer, and the graphene material, wherein the graphene material is liquid crystalline. The graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.
In yet another embodiment, an interpenetrating polymer network is provided. The interpenetrating polymer network comprises a first polymer network comprising a first polymer. The first polymer comprises polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), poly(butylene succinate-co-adipate) (PBSA), polyethersulfone (PES), or combinations thereof. The IPN further comprises a second polymer network comprising a second polymer. The second polymer comprises polydopamine, poly(methacryloyloxylethyl phosphorylcholine) (polyMPC), poly(sulfobetaine methacrylate) (polySBMA), poly(sulfobetaineacrylamide) (polySBAAm), carboxybetaine, sulfobetaine, or combinations thereof. The IPN further comprises a graphene material, wherein the graphene material is liquid crystalline. The graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.
These and other features and advantages of the present disclosure may be appreciated from a review of the following detailed description of the present disclosure, along with the accompanying figures in which like reference numerals refer to like parts throughout.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart that illustrates a process for producing a liquid crystalline interpenetrating polymer network (LC-IPN), in accordance with an exemplary embodiment of the disclosure;
FIG. 2 is FTIR spectra of graphene oxide, functionalized graphene oxide, IPN without functionalized graphene oxide, and liquid crystalline functionalized graphene oxide IPN (LC-IPN), in accordance with an exemplary embodiment of the disclosure; and
FIG. 3 is a plot of zero shear viscosity against a concentration of functionalized graphene oxide in liquid crystalline functionalized graphene oxide IPN (LC-IPN).
Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description of exemplary embodiments is intended for illustration purposes only and is, therefore, not intended to necessarily limit the scope of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS
The following description illustrates some exemplary embodiments of the disclosed disclosure in detail. Those of skill in the art will recognize that there are numerous variations and modifications of this disclosure that are encompassed by its scope. Accordingly, the description of a certain exemplary embodiment should not be deemed to limit the scope of the present disclosure.
The term “comprising” as used herein is synonymous with “including,” or “containing,” and is inclusive or open-ended and does not exclude additional, unrecited elements, or process steps.
All numbers expressing quantities of ingredients, property measurements, and so forth used in the specification are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that may vary depending upon the desired properties sought to be obtained.
As used herein, the term “graphene-based” corresponds to graphene and graphene-derived compounds having 2-dimensional graphene structural units. The “graphene material” of the present disclosure is a specific example of the “graphene-based” compound.
The term, “contaminants”, as used herein, refers to unwanted, or harmful particles such as colloidal particles, persistent organic compounds, pathogenic microorganisms, viruses, salts, molecules, ions, and heavy metals present in water.
A membrane refers to a semi-permeable, physical barrier employed for filtration or separation of particles from gas or liquid phases. In the context of the present disclosure the term “gas or liquid phases” refers to a solution, particularly water-based which needs to be treated (un-treated water) to obtain pure water. The un-treated water can be effluent from industries, agricultural wastewater, sea water, municipal wastewater, and the like. The solution that is fed through the membrane for treatment is otherwise termed “feed water” or “feed solution”. The separation process using the membrane, at times, may be pressure-driven, as in reverse osmosis membrane technology.
The term, “permeability”, as used herein, refers to water permeability and can be defined as the volume of water that passes through a thickness of the membrane per time per transmembrane pressure.
A membrane is typically a porous structure, the term “membrane selectivity”, depending on the type of membrane, is based on pore size and charge on the membrane. The selectivity may also depend on porosity of the membrane. The term, “porosity”, as used herein refers to volume of pores divided by the total volume of the membrane.
The term, “throughput” as used herein, refers to the membrane’s filter capacity and measures the time water will flow continuously through the membrane before the membrane gets clogged.
The term, “high flux” or “pure water flux” as used herein, refers to a volume of water that passes through a surface area of the membrane per time.
The membrane depending on the intended application is chosen based on its permeability, selectivity, and tolerance to fouling. Additionally, the membrane should be mechanically stable to withstand applied pressure and at the same time thin such that a membrane surface area per unit volume is as large as possible. Mechanical stability or toughness may be expressed in terms of storage modulus or elastic modulus.
According to embodiments of the present disclosure, an interpenetrating polymer network is provided. The interpenetrating polymer network (IPN) comprises a first polymer network comprising a first polymer. The first polymer comprises polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), poly(butylene succinate-co-adipate) (PBSA), polyethersulfone (PES), or combinations thereof. The IPN comprises a second polymer network comprising a second polymer. The second polymer comprises polydopamine, poly(methacryloyloxylethyl phosphorylcholine) (polyMPC), poly(sulfobetaine methacrylate) (polySBMA), poly(sulfobetaineacrylamide) (polySBAAm), carboxybetaine, sulfobetaine, or combinations thereof. The IPN comprises a graphene material, wherein the graphene material is liquid crystalline. The graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.
Polymers, that constitute polymer networks to form IPN, are chosen based on their compatibility with each other, in one instance. The compatibility of polymers can be influenced by factors such as chemical structure, functional groups present in the polymers, and solubility in common solvents. The polymers should have different crosslinking mechanisms to facilitate the formation of interpenetrating networks. For example, one polymer may undergo thermal crosslinking while a second polymer may undergo photo-crosslinking or chemical crosslinking reactions. The polymers should be compatible in terms of processing parameters used to fabricate the IPN. The processing parameters include solubility in common solvents, processing temperatures, and compatibility with any additives or processing aids that need to be considered to facilitate interpenetration and crosslinking between the polymer networks.
Overall, the IPN, with the combination of polymers should result in synergistic effects that enhance the performance of the IPN beyond what is achievable by individual polymer networks. According to embodiments of the present disclosure, the inventive IPN exhibits improvement in mechanical strength, thermal stability, chemical resistance, fouling resistance when compared to individual polymer networks.
In one embodiment, the first polymer network comprises the first polymer. The first polymer comprises polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), poly(butylene succinate-co-adipate) (PBSA), polyethersulfone (PES), or combinations thereof. In one embodiment, the first polymer is PVDF.
In one embodiment, the first polymer provides mechanical stability, chemical stability, and rigidity when incorporated into IPN.
The second polymer network comprises a second polymer. The second polymer comprises polydopamine, poly(methacryloyloxylethyl phosphorylcholine) (polyMPC), poly(sulfobetaine methacrylate) (polySBMA), poly(sulfobetaineacrylamide) (polySBAAm), carboxybetaine, sulfobetaine, or combinations thereof. In one embodiment, the second polymer is polydopamine.
In some embodiments, the second polymer is zwitterionic having positive and negative charges, while electrically neutral as a whole. The charges on the second polymer may facilitate favorable hydrogen bonding and electrostatic interactions between the first polymer network and the second polymer network. When used as a membrane for filtration, the charges on the second polymer may facilitate the separation of contaminants.
The first polymer network is compatible with the second polymer network to form the IPN. In one embodiment, a ratio of a weight percent of the first polymer network to the second polymer network in the interpenetrating polymer network is in a range of 1:1 to 3:1. In preferred embodiments, the ratio of the weight percent of the first polymer network to the second polymer network in the interpenetrating polymer network is 2:1. The ratio of the weight percent of the first polymer network to the second polymer network can be fine-tuned based on the intended application. For example, for enhanced mechanical stability of a membrane comprising the IPN, the weight percent of a polymer network that contributes more towards mechanical stability than the other can be increased in the interpenetrating polymer network.
The IPN comprises a graphene material, wherein the graphene material is liquid crystalline. In one embodiment, the graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.
The presence of liquid crystalline graphene material provides mechanical stability to the IPN structure. A membrane incorporating the liquid crystalline graphene material IPN (LC-IPN) allows for higher pressure operation when compared to a membrane based on IPN without the graphene material due to its superior mechanical stability. The superior mechanical stability is due to the ordered, uniform arrangement or alignment of the graphene material in the IPN.
The liquid crystalline graphene material incorporated in IPN, due to its ordered, uniform arrangement associated with liquid crystalline property enhances the overall selectivity when incorporated in a membrane. Further, the LC-IPN may be fine-tuned for selective removal of contaminants by modifying the functional groups present on the graphene material.
Interlayer spacing between layers of graphene sheets of graphene material may be varied based on the preparation method of the graphene material. For example, in the case of graphene oxide (GO), interlayer spacing between GO layers of GOs of different manufacturing origins is different due to varying degrees of oxygenation. The interlayer spacing of graphene material may be tuned sufficiently to exclude selective contaminants using the LC-IPN in a membrane.
Graphene material being inherently antibacterial can inhibit biofouling when used as a membrane, thus preventing the accumulation of contaminants and prolonging the lifetime of the membrane. This is particularly advantageous in applications where fouling is a common issue, such as wastewater treatment and industrial filtration processes.
Membranes based on polymer-supported graphene oxide are known in the art. GO offers many advantages over graphene such as hydrophilicity, incorporation of functional groups thereby enhancing selectivity of the membrane. However, graphene oxide membranes tend to swell up in presence of water thus limiting its usage in aqueous systems. The inventive LC-IPN, due to the interpenetrating polymer network and the liquid crystalline alignment of the graphene material in the IPN may minimize the swelling effect thus making GO more effective as a membrane for aqueous systems.
In one embodiment, a weight percent of the graphene material in the interpenetrating polymer network is in a range of 1 weight percent to 5 weight percent. In preferred embodiments, the graphene material is present in the interpenetrating polymer network in a range of 2 weight percent to 4 weight percent.
As used herein, the term “graphene quantum dot” refers to nanoscale particles of graphene, typically having a diameter of less than 20 nm.
As used herein, the term “graphene oxidation product” corresponds to graphene oxide having various oxygenated functionalities with varying degrees of oxidation. Examples of oxygenated functionalities include carbonyl group (C=O), hydroxyl group (-OH), carboxyl group (-COOH), epoxy group (-O-), or combinations thereof. The oxygenated functionalities may be found attached to basal planes of the layered graphene oxide and/or along the edges of the graphene oxide structure. GO is hydrophilic and the hydrophilicity can be controlled by controlling the degree of oxidation, or by reducing the resulting GO formed. The “graphene oxidation product”, as used herein, also includes reduction products of graphene oxide with a mild reducing agent. In one instance, the mild reducing agent is green tea.
As used herein, the term “functionalized graphene” refers to reaction products of graphene with a reactant. In one embodiment, the reactant comprises 2-isocynatoethyl methacrylate, 2-hydroxyethyl methacrylate, triphenyl porphyrin, or a quaternary ammonium compound. In preferred embodiments, the reactant is 2-isocynatoethyl methacrylate or 2-hydroxyethyl methacrylate. As used herein, the term “functionalized graphene oxidation product” refers to reaction products of graphene oxidation product with the reactant. The reactant comprises 2-isocynatoethyl methacrylate, 2-hydroxyethyl methacrylate, triphenyl porphyrin, or a quaternary ammonium compound. In one embodiment, the graphene material is a mixture of the graphene material with a porous framework architecture. Examples of graphene material in the mixture include graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, or combinations thereof. As used herein, the term “porous framework architecture (POF)” corresponds to 2-dimensional (2D) framework comprising organic monomers linked by strong covalent bonds formed from lightweight, nonmetallic elements such as carbon, hydrogen, nitrogen, boron, oxygen, and silicon. POF includes covalent-organic frameworks (COFs), covalent triazine frameworks (CTFs), amorphous hypercross-linked polymers (HCPs), polymers of intrinsic microporosity (PIMs), conjugated microporous polymers (CMPs), porous aromatic frameworks (PAFs) or combinations thereof. In one embodiment, the porous framework architecture comprises a trialdehyde, benzene-1,3,5-tricarboxaldehyde, 2,4,6-triformylphloroglucinol, a diamine, a triamine, or combinations thereof.
In one embodiment, a weight percent of the porous framework architecture in the mixture of the graphene material with the porous framework architecture is in a range of 0.25 weight percent to 1 weight percent.
Further, keeping in mind the application of the inventive IPN as a filtration media, such as a membrane, the structure and properties of the LC-IPN may be fine-tuned by adjusting the composition and synthesis parameters of its constituent polymer networks. This allows for precise control over the pore size, porosity, surface chemistry, and permeability of the membrane, enabling tailored separation performance for specific filtration applications.
In one embodiment, the first polymer network comprises polyvinylidene fluoride, the second polymer network comprises polydopamine, and graphene material is liquid crystalline functionalized graphene oxidation product.
Embodiments of the present invention provide a method for forming a film comprising an interpenetrating polymer network. FIG. 1 is a flow chart 100 that illustrates the method of forming the film comprising the interpenetrating polymer network through exemplary steps 102 through 108, in accordance with an embodiment of the present disclosure. At step 102, a first mixture is provided, wherein the first mixture comprises a first polymer, and one of a second monomer or a second polymer.
There are many known methods to prepare interpenetrating polymer networks. In a sequential method, a second monomer and optionally crosslinkers and activators are added to a mixture including the first polymer network. The first polymer network is formed first in the sequential method and is followed by the formation of the second polymer network. In a simultaneous method, both monomers of first polymer and second polymer along with crosslinkers and activators are added together and polymerization proceeds through non-interfering reactions. The IPN of the present disclosure may be prepared using either the sequential or the simultaneous method. In a preferred embodiment, the IPN of the present disclosure is prepared using the sequential method.
In one embodiment, the first polymer and a second monomer are dispersed in a first solvent. In another embodiment, the first polymer is dispersed in the first solvent followed by addition of the second polymer.
The first polymer, as used herein, is a pre-polymer as polymerization of the first polymer and the formation of the first polymer network continues through steps 102 to 106. The second polymer, as used herein, is a pre-polymer as polymerization of the second polymer and the formation of the second polymer network continues through steps 102 to 108. The term, “pre-polymer”, as used herein refers to an intermediate polymer product that can further polymerize with an increase in degree of polymerization to obtain a final polymer. The “degree of polymerization” as used herein, corresponds to a number of monomers or monomeric units in a polymer. An extent of IPN formation is directly proportional to the degree of polymerization of the first polymer network and the second polymer network. In one instance, the degree of polymerization, or the extent of IPN network formation decides a pore size of the IPN.
In one embodiment, the first polymer, and the second monomer or second polymer are taken together in a first solvent and heated to a temperature in a range of 75 to 90 °C with mechanical agitation for a period of time in a range of 6 to 24 hours to obtain the first mixture. The first mixture is degassed to remove any dissolved air or gases. In another embodiment, the first polymer is taken in the first solvent followed by addition of the second monomer, or the second polymer, with agitation at a temperature in a range of 75 to 90 °C for a period of time in a range of 6 to 24 hours followed by degassing to obtain the first mixture.
Examples of the first solvent include, but are not limited to, N, N-dimethyl formamide (DMF), N-Methyl-2-pyrrolidone (NMP), N, N-dimethyl acetamide (DMAC), gamma-butyrolactone, dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone, or any combinations thereof. In one embodiment, the first solvent is DMF.
The first mixture may additionally include crosslinkers and activators. Examples of crosslinkers include, but are not limited to, N, N-methylene bis(acrylamide), bisphenol A diglycidyl ether (BADGE), polyethylene glycol dimethacrylate (PEGDMA), ethylene glycol dimethacrylate (EGDMA), trimethylolpropane triacrylate (TMPTA), tetraethylene glycol dimethacrylate (TEGDMA), diethylene glycol dimethacrylate (DEGDMA), hexamethylene diisocyanate (HMDI), divinylbenzene (DVB), methacrylic anhydride or combinations thereof.
Examples of activators include, but are not limited to, benzoyl peroxide (BPO), azzobisisobutyronitrile (AIBN), dicumyl peroxide (DCP), ammonium persulfate (APS) with N,N,N',N'-tetramethylethylenediamine (TEMED), benzophenone (BP), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO) or combinations thereof.
At step 104, a dispersion comprising a graphene material is provided in the first mixture under agitation at a temperature in a range of 60 °C to 80 °C to form a homogenous mixture.
The dispersion comprises a second solvent. The graphene material is dispersed in the second solvent to form the dispersion.
The first solvent and the second solvent are the same, in one embodiment. In another embodiment, the first solvent and the second solvent are different but they are compatible with the first polymer, the second polymer and the graphene material. Examples of the second solvent include, but are not limited to, N, N-dimethyl formamide (DMF), N-methyl-2-pyrrolidone (NMP), N, N-dimethyl acetamide (DMAC), gamma-butyrolactone, dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone, or any combinations thereof. In one embodiment, the second solvent is DMF.
Examples of graphene material include graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.
In embodiments where the graphene material is functionalized graphene or functionalized graphene oxidation product, the graphene material reacts with a reactant. The reactant is decided based on functional groups desired on the graphene material. The reaction with the reactant and the functionalized graphene or functionalized graphene oxidation product may proceed in presence of a catalyst.
Examples of catalyst include, but are not limited to, dibutyltin dilaurate (DBTDL), dibutyltin diacetate (DBTDA), 4-dimethylaminopyridine (DMAP), dibutyltin oxide (DBTO), titanium-based catalysts, zirconium-based catalysts, zinc acetate or combinations thereof. In one embodiment, the catalyst is dibutyltin dilaurate.
Examples of reactants include 2-isocynatoethyl methacrylate, 2-hydroxyethyl methacrylate, triphenyl porphyrin, a quaternary ammonium compound, or combinations thereof. In one embodiment, the reactant is 2-isocynatoethyl methacrylate, 2-hydroxyethyl methacrylate, or combinations thereof.
The dispersion comprising the graphene material is provided in the first mixture under agitation at a temperature in a range of 60 °C to 80 °C to form a homogenous mixture. In one embodiment, agitation is achieved by magnetic stirring to form the homogenous mixture. Other techniques such as centrifugation, and ultrasonication may be utilized to form the homogenous mixture. The agitation provides the shear stress required for the formation of liquid crystalline graphene material, at step 104. It is a particular advantage of the present disclosure, that the liquid crystalline phase of graphene material is achievable in the homogeneous mixture at low concentrations of graphene material. In one embodiment, the low concentration of graphene material corresponds to a concentration range of 1 milligram per milliliter (mg/mL) to 2.5 mg/mL of the graphene material in the dispersion, provided at step 104. The formation of liquid crystalline phase of graphene material on application of shear stress may be due to the presence of interpenetrating polymer network.
The graphene material exists in a nematic phase under shear stress generated due to agitation thus exhibiting liquid crystalline property. At step 104, extent of interpenetrating polymeric network formation, i.e., degree of polymerization of first and second polymer networks, is more than the extent of interpenetrating polymeric network formation when compared to the preceeding step.
At step 106, the homogeneous mixture is cast to form a layer over a substrate. The casting may be performed using a doctor blade to form a uniform layer of desired thickness. However, other methods for forming films as known in the art may be utilized, such as dip coating.
Examples of substrates include, but are not limited to, polymers like polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polycarbonate (PC); glass, ceramic, metal, or combinations thereof. In one embodiment, the substrate is glass.
The cast layer includes the liquid crystalline graphene material. The graphene material existing in nematic phase at step 104, changes from nematic phase to a more ordered lamellar phase in step 106. Additionally, the degree of polymerization of the first polymer, and the second monomer or the second polymer increases, at step 106, and this is more pronounced for second polymer network.
At step 108, the substrate comprising the layer is immersed in a coagulating bath to obtain a film. The terms, “film”, “liquid crystalline film”, “liquid crystalline interpenetrating polymer network (LC-IPN) film”, are similar and are interchangeably used throughout the specification, unless otherwise specified. The film comprises the liquid crystalline interpenetrating polymer network (LC-IPN), wherein the interpenetrating polymer network comprises a first polymer network comprising the first polymer, a second polymer network comprising the second polymer, and the graphene material, wherein the graphene material is liquid crystalline, and wherein the graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.
The coagulating bath comprises water, a buffer solution, a mixture of an alcohol and water, or combinations thereof.
The period of time for which the substrate is immersed in the coagulating bath is decided based on the extent of interpenetrating polymer network formation desired for the film. This is because the extent of the interpenetrating polymer network may govern the pore size of the film.
Microfiltration membranes are known to have a pore size in a range of 0.1 to 10 microns while for ultrafiltration it is in a range of 0.01 to 1 micron. The pore size of nanofiltration membrane is in a range of 0.001 to 0.01 micron and for reverse osmosis the membrane should have a pore size of less than about 0.001 micron. According to embodiments of the present disclosure, the pore size of the inventive LC-IPN can be in a range of 10 microns to 1 micron, preferably 0.001 micron to 1 micron, and more preferably less than 0.001 micron. Accordingly, the time period for which the substrate is immersed in the coagulating bath may vary from 2 days to obtain micro-sized pores to 7 to 10 days for nano-scale pores.
The film obtained at step 108, may be dispersed in a solvent to form LC-IPN dispersion, where LC-IPN exists in liquid form. The IPN structure and liquid crystallinity are preserved in the LC-IPN dispersion. In the case of GO, liquid crystallinity has been demonstrated in concentrated dispersions and a similar strategy may be employed to obtain GO-based IPN in liquid form.
The method as illustrated in FIG. 1, may be utilized for large-scale, continuous, high-speed operation to produce the film. The size of the film that can be formed is only limited by a size of the casting equipment, thus large-area films can be produced with relative ease.
The liquid crystalline film has a thickness in a range of 75 to 300 microns. In one embodiment, the film has a thickness in a range of 90 to 200 microns.
The film, due to the presence of graphene material exhibits antibacterial activity. In a controlled study, the film exhibited inhibition in growth of bacteria such as Escherichia coli (E Coli) and Staphylococcus aureus (S Aureus), when contacted with the film. In one embodiment, the film exhibits anti-bacterial property, antifouling property, chlorine tolerance property, or combinations thereof.
In some embodiments, the liquid crystalline film has a storage modulus in a range of 140 megaPascal (MPa) to 200 MPa.
In some embodiments, the film has an ion rejection percentage of greater than 97% when used for molecular sieving. Non-limiting examples of ions include monovalent and divalent ions of metals, and salts such as sodium sulfate, magnesium sulfate, magnesium chloride and sodium chloride.
The liquid crystalline film, in one embodiment, has a water flux in a range of 100 litres per square meter per hour (LMH) to 150 LMH.
The primary objective of the present disclosure is the use of the liquid crystalline film as a membrane for filtration, or molecular sieving. However, considering the unique properties of the IPN, or film comprising IPN many other applications may be envisaged. For example, the antibacterial nature of the liquid crystalline film can be exploited for use as antibacterial films over touch screens, protective coatings, implantable devices, electronic devices, or in packaging. The liquid crystalline film exhibited cytocompatibility which means that structure or function of body tissue is not altered upon contact with the film. Thus, the liquid crystalline film may find potential application as a biomaterial.
The film as obtained from step 108, is washed thoroughly with ultrapure water before use. For use as a filtration media, such as the membrane, the film may be further washed in acidic or basic media as per the protocol followed for membrane incorporation in a filtration system. The washing with acidic and basic media will help in developing charges on membrane surface as required for the intended application. The application of the membranes includes, but is not limited to, wastewater treatment, treatment of industrial effluents, desalination, separation of contaminants, gas separation, or oil-water separation.
The incorporation of multiple polymer networks with different chemical functionalities along with liquid crystalline graphene material that constitutes the inventive LC-IPN when employed as a membrane can enhance its selectivity towards specific molecules or ions. By careful selection of polymers with complementary affinity towards target species or incorporating functional groups for molecular recognition, the inventive LC-IPN membranes can achieve higher separation efficiency and purity.
LC-IPN membranes can exhibit improved resistance to fouling compared to conventional membranes. The interpenetrating polymer network creates a complex and tortuous structure that hinders the adhesion and accumulation of foulants, thereby reducing membrane fouling and prolonging operational lifespan in filtration applications.
The incorporation of liquid crystalline graphene material in the IPN provides yet another handle to address fouling. Further, the combination of liquid crystalline graphene material and porous framework architecture, possesses inherent capabilities to improve the structured arrangement of membranes and enhance their antimicrobial and hydrophilic properties. The remarkable attribute directly tackles fouling, which is a major concern associated with commercial membranes.
Depending on the choice of polymers and the graphene material used in the LC-IPN, the membranes comprising these can offer excellent chemical and thermal stability, making them suitable for filtration processes involving harsh chemical environments or elevated temperatures. Further, the hydrophilicity, hydrophobicity, and antifouling properties of the membranes comprising LC-IPN may be fine-tuned.
In one embodiment, a filtration system incorporating the liquid crystalline film is provided, where the liquid crystalline film functions as a membrane. “The filtration system”, as used herein, refers to membrane-based systems employed for separation, or filtration of contaminants, foulants, or ions from aqueous solutions, including, but not limited to, microfiltration, nanofiltration, ultrafiltration, and reverse osmosis systems. The “membrane”, as used herein, refers to the inventive liquid crystalline film when used for filtration, or separation of contaminants, ions, or foulants from aqueous solutions. The inventive membrane is support-free. A typical graphene-based filtration membrane includes a graphene-based film that functions as a sieve, and a porous and more permeable support that provides mechanical strength. As used herein, the term “support-free” refers to the membrane that exhibits sufficient mechanical stability to be used without a support, as opposed to polymer-supported membranes.
In some embodiments, the membrane comprising the liquid crystalline film has a water flux in a range of 100 LMH to 150 LMH.
In some embodiments, the membrane has a storage modulus in a range of 140 MPa to 200 MPa.
The membrane comprising the liquid crystalline film has a flux recovery ratio of 98%. In comparison, a membrane, or a film, comprising IPN without the graphene material has a flux recovery ratio of 85%. The term, “flux recovery ratio” in percentage refers to a ratio of pure water flux of a cleaned membrane to pure water flux.
The membrane comprising the liquid crystalline film has a sodium chloride salt rejection of about 97%, a sodium sulfate salt rejection of 99.2%, and a magnesium sulfate salt rejection of about 99.8%.
The membrane comprising the liquid crystalline film exhibits efficient dye molecule rejection. In one embodiment, the liquid crystalline film and the membrane exhibit 100% rejection of dye molecules, such as methylene blue (MB) and Congo red (CR).
The membrane comprising the liquid crystalline film is efficient in rejecting antibiotics that are commonly present in our water systems such as amoxicillin and azithromycin. The membrane has an antibiotics rejection in a range of 97 to 98 %.
The membrane comprising the liquid crystalline film is recyclable up to 4 to 6 times.
The membrane comprising the liquid crystalline film exhibits chlorine tolerance.

EXAMPLES
EXAMPLE 1
Preparation of functionalized graphene oxide
About 0.2 to 0.4 grams (g) of graphene oxide (GO) was dispersed in dry DMF and sonicated for 30 minutes to form a dispersion. About 2 mmole of 2-isocynatoethyl methacrylate was added dropwise in the dispersion. DBTDL catalyst was added to the dispersion to form the reaction mixture. The reaction mixture was stirred at room temperature for 24 hours under nitrogen atmosphere to form GO functionalized with 2-isocynatoethyl methacrylate (GO-X) as a dispersion. After 24 hours, the dispersion was washed and centrifuged using THF and was then vacuum dried at 60 °C to obtain the functionalized graphene oxide powder (GO-X), termed as Sample 1.

EXAMPLE 2
Preparation of IPN without liquid crystalline graphene
A mixture of 2 grams of PVDF and 1 gram of dopamine monomer was combined with 7 ml of DMF to form a solution with a concentration of 30 wt%. The solution was then heated to 80°C and mechanically agitated until a uniform, mixture was obtained. To eliminate any remaining bubbles, the mixture was thoroughly degassed. The mixture was then cast onto a glass plate using a 300 µm doctor blade, with a casting speed of 7 cm/s to form a layer. The glass plate having the layer was placed in a coagulating bath containing a cold Tris buffer solution (10 mM, pH=8.5) and sodium iodate (NaIO4 (5 mM)) at a temperature of approximately 4°C. The layers were allowed to remain immersed in the buffer solution for a duration of 7 days to form the film comprising IPN. The film was thoroughly rinsed and washed with ultra-pure water to obtain Sample 2.

EXAMPLE 3
Preparation of liquid crystalline functionalized graphene oxide IPN
A mixture of 2 grams of PVDF and 1 gram of dopamine monomer was combined with 7 ml of DMF to form a solution with a concentration of 30 wt%. The solution was then heated to 80°C and mechanically agitated until a uniform, mixture was obtained. To eliminate any remaining bubbles, the mixture was thoroughly degassed. About 1.65 to 2.5 wt% of GO-X (obtained from Example 1) was dispersed in 3 ml of DMF to form dispersions having varying concentrations. The dispersion was added to the mixture to form a homogenized mixture. The homogenized mixture was then cast onto a glass plate using a 300 µm doctor blade, with a casting speed of 7 cm/s to form a layer. The glass plate having the layer was placed in a coagulating bath containing a cold Tris buffer solution (10 mM, pH=8.5) and sodium iodate (NaIO4 (5 mM)) at a temperature of approximately 4°C. The layers were cast from different dispersions and were allowed to remain immersed in the buffer solution for a duration of 7 days to form the film comprising IPN. The film was thoroughly rinsed and washed with ultra-pure water to obtain Sample 3.

Characterization of Samples 1 to 3
XRD Analyses:
X-ray diffraction (XRD) was carried out on a PANalytical X'pert pro using Cu Ka source operating at 40 kV and 30 mA in the 2? range of 10-80° and at a scan rate of 0.04 s-1. The analysis of the data was performed using LaboTex software.
The XRD analyses were conducted on graphene oxide (GO), and Samples 1 to 3. Pure GO displayed a prominent peak at 9.94°, corresponding to the (001) plane, with an interlayer distance of 0.89 nm. Upon conversion to partially crystalline GO-X (Sample 1 corresponding to functionalized graphene oxide (GO-X) of Example 1), the peak shifted to a higher 2 theta value of 14.36°, indicating a reduced interlayer distance of 0.62 nm. Furthermore, the presence of a weak new peak at 30.68° (0.29 nm) suggested reduction of GO. The IPN membrane without graphene material (Sample 2 corresponding to IPN without graphene of Example 2) exhibited a peak at approximately 20.56º, which arises from the semi-crystalline PVDF. Sample 3 (liquid crystalline functionalized graphene-based IPN of Example 3) exhibited peaks corresponding to both GO-X and IPN (Sample 2), confirming the successful incorporation of partially reduced GO-X into the IPN matrix. The IPN matrix preserved the reduced d-spacing of GO-X as well as the liquid crystalline phase.
FTIR Analyses:
FTIR spectra were recorded of graphene oxide, Sample 1 (functionalized graphene oxide (GO-X) of Example 1), Sample 2 (IPN without graphene of Example 2), and Sample 3 (liquid crystalline functionalized graphene-based IPN of Example 3). FTIR spectra were recorded on a Perkin Elmer frontier spectrometer in transmittance mode by accumulating 16 scans over a range of 600 to 4000 cm-1 wavenumber.
FIG. 2 is the FTIR spectra 200 where 210 corresponds to FTIR spectrum of neat graphene oxide, 220 corresponds to FTIR spectrum of Sample 1 (functionalized graphene oxide), 230 corresponds to FTIR spectrum of Sample 2 (IPN without graphene), and 240 corresponds to Sample 3 (liquid crystalline functionalized graphene-based IPN). FTIR spectrum 220 (functionalized graphene oxide) had characteristic peaks of GO at 3200, 1721, 1612 and 1044 cm-1, corresponding to -OH group stretching, -C=O, C=C and C-O stretching, respectively. Additionally, the spectrum showed two new peaks at 1295 and 1167 cm-1 for the stretching vibrations of amide C-O and C-N indicating the presence of 2-isocyanatoethyl methacrylate group. The absence of any isocyanate peaks (~2275-2263 cm-1) confirmed covalent bond formation between the GO and 2-isocyanatoethyl methacrylate. Referring to FIG. 2, the spectrum 240 (liquid crystalline functionalized graphene-based IPN), the spectrum showed two new strong peaks at 1402 and 1167 cm-1, corresponding to strong -CH2 bending and -CF2 stretching of PVDF, respectively. A broad hump around 3369 cm-1 due to -OH and -NH stretching and two peaks centered around 1630-1548 cm-1 from the scissoring as well as bending vibrations of N-H bonds, were attributable to polydopamine. The overlapping and slight peak shifting of the spectrum 240 when compared to spectrum 230 indicates the successful inclusion of the liquid crystalline functionalized graphene in the IPN.
Polarized optical microscopy (POM) Analyses:
The polarized optical microscopy (POM) technique was employed to examine the phase morphology of the functionalized graphene oxide IPN dispersion at different concentrations of functionalized graphene oxide in dimethylformamide (DMF) (corresponding to Example 3), and IPN dispersion (corresponding to Example 2, without graphene). IPN dispersion exhibited no birefringence, indicating the absence of liquid crystalline property.
Small-Angle X-Ray Scattering (SAXS):
SAXS measurements were conducted on a XEUSS SAXS SYSTEM. SAXS was performed within specific scattering factor q ranges (q = 2p/d = 4p sin ?/?). Lorentz Correction Kratky plot (Kratky plot) (Iq2 vs. q) was used to obtain structural information regarding functionalized graphene oxide dispersion (Sample 1) and the functionalized graphene oxide IPN film (Sample 3). The Kratky plots of functionalized graphene oxide dispersion (corresponding Example 3) having a concentration of 7.5 mg/ml of graphene material exhibited distinct diffusive patterns and broad scattering peaks at qnem = 0.056/0.074 Å-1, indicating a highly ordered nematic phase. In the case of functionalized graphene oxide IPN film (Sample 3), less intense broad peaks at 0.42 Å-1 and 0.50 Å-1 were observed, which indicated the preservation of the nematic phase of functionalized graphene oxide in the functionalized graphene oxide IPN film. Two additional peaks near 0.106 Å-1 and 0.116 Å-1 were observed in the functionalized graphene oxide IPN film, indicating the existence of a lamellar phase. The combination of the nematic and lamellar phases in the functionalized graphene oxide IPN film demonstrated that the high-order nematic and lamellar phases were solely derived from the incorporation of graphene material into the IPN.
Rheological Studies:
Rheological studies were conducted on functionalized graphene oxide IPN dispersion at various concentrations (corresponding to Example 3) to understand the viscoelastic behavior. The complex viscosity of the functionalized graphene oxide IPN dispersions was conducted as a function of shear rate for various concentrations of the dispersions. The behavior of the fluid, whether Newtonian or non-Newtonian (shear thinning), is dependent on the concentration of the dispersion. At low shear rates, the nematic phases within the functionalized graphene oxide IPN dispersion were randomly distributed and not aligned, resulting in higher viscosity. However, at high shear rates, the randomly distributed nematic phases of GO-X sheets align in the direction of shear stress, leading to reduced physical interaction and a decrease in complex viscosity.
FIG. 3 is a plot 300 of zero shear viscosity (Pascal seconds) plotted against various concentrations of functionalized graphene oxide (GO-X) in liquid crystalline functionalized graphene oxide IPN (LC-IPN). At low concentrations (? = 0.25 mg/ml), the functionalized graphene oxide IPN dispersion in DMF exists in the isotropic phase, and the viscosity increases until it reaches a specific concentration ?c, approximately 1 mg/ml, where it reaches a maximum. As the concentration of functionalized graphene oxide increases beyond ?c, the complex viscosity decreases, reaching a minimum before increasing again. The decrease in zero shear viscosity is attributable to the formation of a less viscous nematic liquid crystalline phase of GO-X. The transition from the isotropic to the nematic phase occurs at a concentration of ?c = 2.5 mg/ml in the case of GO-X. Similar studies may be performed for each of the graphene materials of the disclosure to arrive at the ideal concentration at which liquid crystalline behavior exists.
Dynamic mechanical analyses (DMA):
A comparative DMA study was performed to gauge the effectiveness of the inclusion of functionalized graphene oxide in IPN matrix in terms of mechanical robustness or stability. From the storage modulus versus temperature plots, it was observed that the presence of functionalized graphene oxide sheets increased the storage modulus of IPN without functionalized graphene oxide (Sample 2) from 140 MPa to nearly 200 MPa for LC-IPN (Sample 3). The enhanced storage modulus is due to the presence of the oriented liquid crystalline graphene in LC-IPN.
Film characterization:
Sample 3 (liquid crystalline functionalized graphene-based IPN of Example 3) films were characterized for their utility as a membrane for filtration. Sample 3 films had a flux recovery ratio of 98%, or more than 98%.
The films (sample 3) had a sodium chloride salt rejection of about 97%, a sodium sulfate salt rejection of 99.2%, and a magnesium sulfate salt rejection of about 99.8%.
Sample 3 films exhibited a dye rejection of 100% of dyes such as methylene blue (MB) and Congo red (CR).
It is to be understood that the above description is intended to be illustrative, and not restrictive. Furthermore, many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. Although the present disclosure has been described with reference to specific exemplary embodiments, it will be recognized that the disclosure is not limited to the embodiments described, but can be practiced with modification and alteration within the scope of the appended claims. , Claims:We claim:
1. A liquid crystalline film comprising an interpenetrating polymer network, the interpenetrating polymer network comprising:
a first polymer network comprising a first polymer, wherein the first polymer comprises polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), poly(butylene succinate-co-adipate) (PBSA), polyethersulfone (PES), or combinations thereof;
a second polymer network comprising a second polymer, wherein the second polymer comprises polydopamine, poly(methacryloyloxylethyl phosphorylcholine) (polyMPC), poly(sulfobetaine methacrylate) (polySBMA), poly(sulfobetaineacrylamide) (polySBAAm), carboxybetaine, sulfobetaine, or combinations thereof; and
a graphene material, wherein the graphene material is liquid crystalline, and wherein the graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.

2. The liquid crystalline film as claimed in claim 1, wherein a weight percent of the graphene material in the interpenetrating polymer network is in a range of 1 weight percent to 5 weight percent.

3. The liquid crystalline film as claimed in claim 1, wherein a ratio of a weight percent of the first polymer network to the second polymer network in the interpenetrating polymer network is in a range of 1:1 to 3:1.

4. The liquid crystalline film as claimed in claim 1, wherein the porous framework architecture comprises a trialdehyde, benzene-1,3,5-tricarboxaldehyde, 2,4,6-triformylphloroglucinol, a diamine, a triamine, or combinations thereof.

5. The liquid crystalline film as claimed in claim 1, wherein a weight percent of the porous framework architecture in the mixture of the graphene material with the porous framework architecture is in a range of 0.25 weight percent to 1 weight percent.

6. The liquid crystalline film as claimed in claim 1, wherein the functionalized graphene, or functionalized graphene oxidation product is a reaction product of graphene, or graphene oxidation product with a reactant, and wherein the reactant comprises 2-isocynatoethyl methacrylate, 2-hydroxyethyl methacrylate, triphenyl porphyrin, or a quaternary ammonium compound.

7. The liquid crystalline film as claimed in claim 1, wherein the first polymer network comprises polyvinylidene fluoride, the second polymer network comprises polydopamine, and graphene material is liquid crystalline functionalized graphene oxidation product.

8. The liquid crystalline film as claimed in claim 1, wherein the liquid crystalline film has a thickness in a range of 75 micrometers (µm) to 300 µm.

9. The liquid crystalline film as claimed in claim 1, wherein the liquid crystalline film has a storage modulus in a range of 140 megaPascal (MPa) to 200 MPa.

10. The liquid crystalline film as claimed in claim 1, wherein the liquid crystalline film exhibits an anti-bacterial property, an antifouling property, a chlorine tolerance property, or combinations thereof.

11. A filtration system incorporating the liquid crystalline film as claimed in claim 1, wherein the liquid crystalline film functions as a membrane, and wherein the membrane is support-free.

12. The filtration system as claimed in claim 11, wherein the membrane has a water flux in a range of 100 LMH to 150 LMH, and a storage modulus in a range of 140 MPa to 200 MPa.

13. The filtration system as claimed in claim 11, wherein the membrane exhibits an antibacterial property, an antifouling property, a chlorine tolerance property, or combinations thereof.

14. A method of forming a liquid crystalline film comprising an interpenetrating polymer network, the method comprising:
providing a first mixture (102), wherein the first mixture comprises a first polymer, and one of a second monomer or a second polymer;
providing a dispersion (104) comprising a graphene material into the first mixture under agitation at a temperature in a range of 60 °C to 80 °C to form a homogenous mixture;
casting the homogeneous mixture (106) to form a layer over a substrate; and
immersing the substrate comprising the layer (108) in a coagulating bath to obtain the liquid crystalline film, wherein the film comprises the interpenetrating polymer network, wherein the interpenetrating polymer network comprises a first polymer network comprising the first polymer, a second polymer network comprising the second polymer, and the graphene material, wherein the graphene material is liquid crystalline, and wherein the graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.

15. The method as claimed in claim 14, wherein the first polymer comprises polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), poly(butylene succinate-co-adipate) (PBSA), polyethersulfone (PES), or combinations thereof, and wherein the second polymer comprises polydopamine, poly(methacryloyloxylethyl phosphorylcholine) (polyMPC), poly(sulfobetaine methacrylate) (polySBMA), poly(sulfobetaineacrylamide) (polySBAAm), carboxybetaine, sulfobetaine, or combinations thereof.

16. The method as claimed in claim 14, wherein a ratio of a weight percent of the first polymer network to the second polymer network in the interpenetrating polymer network is in a range of 1:1 to 3:1, and wherein a weight percent of the graphene material in the interpenetrating polymer network is in a range of 1 weight percent to 5 weight percent.

17. The method as claimed in claim 14, wherein providing the first mixture comprises:
adding the first polymer in a first solvent followed by addition of the second monomer, or the second polymer, with agitation at a temperature in a range of 70 to 100 °C for a period of time in a range of 6 to 24 hours; and
degassing the first solvent to obtain the first mixture.

18. The method as claimed in claim 14, wherein the first solvent and the second solvent, independently, comprise N,N-dimethyl formamide (DMF), N-Methyl-2-pyrrolidone (NMP), N,N-dimethyl acetamide (DMAC), gamma-butyrolactone, dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone, or any combinations thereof.

19. The method as claimed in claim 14, wherein the functionalized graphene, or functionalized graphene oxidation product is a reaction product of graphene, or graphene oxidation product with a reactant, and wherein the reactant comprises 2-isocynatoethyl methacrylate, 2-hydroxyethyl methacrylate, triphenyl porphyrin, or a quaternary ammonium compound.

20. The method as claimed in claim 14, wherein immersing the substrate in the coagulating bath comprises immersing over a period of time followed by washing with water to obtain the film.

21. The method as claimed in claim 14, wherein the coagulating bath comprises water, a buffer solution, a mixture of an alcohol and water, or combinations thereof.

22. An interpenetrating polymer network comprising:
a first polymer network comprising a first polymer, wherein the first polymer comprises polyvinylidene fluoride (PVDF), polyvinyl butyral (PVB), poly(butylene succinate-co-adipate) (PBSA), polyethersulfone (PES), or combinations thereof;
a second polymer network comprising a second polymer, wherein the second polymer comprises polydopamine, poly(methacryloyloxylethyl phosphorylcholine) (polyMPC), poly(sulfobetaine methacrylate) (polySBMA), poly(sulfobetaineacrylamide) (polySBAAm), carboxybetaine, sulfobetaine, or combinations thereof; and
a graphene material, wherein the graphene material is liquid crystalline, and wherein the graphene material comprises graphene quantum dots, graphene oxidation product, functionalized graphene, functionalized graphene oxidation product, a mixture of the graphene material with a porous framework architecture, or combinations thereof.

23. The interpenetrating polymer network as claimed in claim 22, wherein a ratio of a weight percent of the first polymer network to the second polymer network in the interpenetrating polymer network is in a range of 1:1 to 3:1, and wherein a weight percent of the graphene material in the interpenetrating polymer network is in a range of 1 weight percent to 5 weight percent.

24. The interpenetrating polymer network as claimed in claim 22, wherein the porous framework architecture comprises a trialdehyde, benzene-1,3,5-tricarboxaldehyde, 2,4,6-triformylphloroglucinol, a diamine, a triamine, or combinations thereof.

25. The interpenetrating polymer network as claimed in claim 22, wherein a weight percent of the porous framework architecture in the mixture of the graphene material with the porous framework architecture is in a range of 0.25 weight percent to 1 weight percent.

26. The interpenetrating polymer network as claimed in claim 22, wherein the functionalized graphene, or functionalized graphene oxidation product is a reaction product of graphene, or graphene oxidation product with a reactant, and wherein the reactant comprises 2-isocynatoethyl methacrylate, 2-hydroxyethyl methacrylate, triphenyl porphyrin, or a quaternary ammonium compound.