WO2008106323A2 - A high throughput screening method and apparatus to produce modified polymers particularly membranes - Google Patents

Abstract

The present invention discloses a method of screening forms of monomers for effects of their polymers on a filter This involves providing a multiple well filter, applying a monomer solution to one or more wells of the filter, polymerizing the monomer to produce a polymer-modified filter, evaluating the polymer-modified filter's performance, and comparing the performance of the polymer-modified filter to the performance of the filter to determine the effect that the polymerizing the monomer has on the performance of the filter The present invention also relates to a method of producing a polymer-modified, multiple well filter and to an apparatus for screening forms of monomers for effects of their polymers on a filter Also disclosed is a product which includes various monomers polymerized to a polyethersulfone as well as a method of producing such modified polyethersulfones

Description

A HIGH THROUGHPUT SCREENING METHOD AND APPARATUS TO PRODUCE MODIFIED POLYMERS, PARTICULARLY MEMBRANES

[0001] This application claims the benefit of U.S. Provisional Patent

Application Serial No. 60/904,032, filed February 28, 2007, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention is directed to a high throughput screening method and apparatus to produce modified polymers, particularly membranes.

BACKGROUND OF THE INVENTION

[0003] Limitations of commercial membranes indicate a need for new polymeric materials with appropriate surface or functional characteristics. Developing such materials for different membrane filtration applications involves great effort, expense, and time. As a result, over the past 30 years, few new polymers have been used for membrane production. Furthermore, prediction of ideal surface or functional characteristics for specific feed composition is not possible with the current state of theoretical surface chemistry.

[0004] A major obstacle in the incorporation of membrane processes into industrial operations is the problem of flux decline due to fouling during the ultrafiltration of biologically-derived products such as proteins and natural organic matter (NOM) found in lakes, rivers, oceans, and groundwater. Fouling not only decreases membrane permeability which reduces productivity due to longer filtration times, but also shortens membrane life due to the harsh chemicals necessary for cleaning. Furthermore, fouling can alter membrane selectivity and lead to significant product loss through denaturation of the proteins. It is highly desirable to have a membrane (fouling) testing procedure that is short in duration, utilizes a minimum amount of test solution, only requires a small membrane area, and is representative of the large-scale process.

[0005] While the exact mechanism of flux loss during protein filtration is not clear, the general consensus seems to be that the main causes are: osmotic back-pressure from concentration polarization, adsorption or deposition of proteins on the surface or in the pores, and compaction or consolidation of the adsorbed protein layer on the upstream side of the membrane. Fouling is the reversible and irreversible adsorption and deposition of proteins and protein aggregates on the membrane surface and in the pores. This causes narrowing or plugging of membrane pores, which results in decreased membrane permeability. Irreversible fouling causes flux loss that is recovered only through the use of harsh detergents and/or chemicals. Flux loss caused by reversible protein fouling, however, is temporary for the protein can easily be removed by rinsing the membrane with water. Furthermore, after some time and under the right operating and solution conditions, further flux loss can occur because the adsorbed protein layer(s) can consolidate or compact into a more dense, higher flux -resistant layer.

[0006] To reduce and remove flux loss, UV-assisted grafting of a monomer onto a membrane has been implemented. Grafting consists of attaching a smaller chemical unit to a main molecular chain. In the past, photoinitiators were used to initiate free radical polymerization at the membrane surface. However, the preferred method of attachment is by UV irradiation rather than plasma or chemical means, which has the advantages of simplicity and short reaction time. UV radiation is generally considered to have a wavelength range from 100 to 450 nm. UV irradiation can crosslink polymer chains and cleave polymer bonds, forming functional groups such as hydroxyls, carbonyls, or carboxylic acids on the membrane surface. Chemical bonds in the membrane polymer are cleaved directly. Free radical sites can be formed on the membrane surface through the cleavage of polymer bonds. When vinyl monomers are present, free radical graft polymerization occurs at these sites, forming polymer chains that are covalently bonded to the surface.

[0007] U.S. Patent No. 5,468,390 to Crivello et al; Yamagishi et al,

"Development of a Novel Photochemical Technique for Modifying Poly (arylsulfone) Ultrafiltration Membranes," JMemb Sci 105:237-247 (1995); and Yamagishi et al., "Evaluation of Photochemically Modified poly (arylsulfone) Ultrafiltration Membranes," JMemb Sci 105:249-259 (1995), disclose modified aryl polysulfone membranes having a hydrophilic vinyl monomer chemically grafted to their pore wall surfaces. An unmodified membrane is contacted with a solution of the monomer and is exposed to ultraviolet light to effect photochemical grafting in the absence of a sensitizer or a free radical initiator. The monomers utilized function to render only the polysulfone membrane pore wall surface hydrophilic. The remaining portion of the membrane solid matrix comprises unmodified polysulfone. These surface-modified membranes are not rewettable after they have been dried and, if dried, lose significant permeability. Therefore, it is necessary to keep the membrane surfaces wet prior to use. U.S. Patent No. 5,468,390 to Crivello et al. specifically discloses membrane compositions which can be used for ultrafiltration and micro filtration membranes and which exhibit low or non- fouling characteristics.

[0008] Japanese Patent No. JP-A-2-59029, published Feb. 28, 1990, discloses a process for modifying a polysulfone porous membrane on its pore wall surface only with a polymerizable monomer by immersing the membrane in the monomer solution and irradiating the solution with ultraviolet light (called the immersion technique). The process is conducted under conditions such that any solvent used in the process does not dissolve the polysulfone membrane. As a result of the process, only the pore wall surface of the porous membrane is modified to render it hydrophilic when hydrophilic polymerizable monomers are utilized in the process.

[0009] However, recent testing has shown that even though UV-assisted graft polymerization achieved by the immersion technique successfully decreased fouling of membrane by imparting hydrophilicity to the surface, the membrane permeability was found to decrease sharply after modification due to blockage of the pores by the grafted polymer chains, caused by high chain density and long grafted chains. A necessary balance is sought between sufficient surface hydrophilicity for low fouling and higher membrane permeability. Furthermore, polysulfone membranes are not very photoactive (e.g., bonds are less easily broken), and therefore, are more difficult to modify. Accordingly, a modified membrane is desired that has high photoactivity, high graft density of short chains on its surface, exhibits low protein fouling, and maintains a greater fraction of the original membrane permeability after modification. [00010] Furthermore, the immersion technique used in the prior art requires a large amount of monomer and is less adaptable to continuous processes on an industrial scale. Also, the immersion technique used in the prior art results in a high UV absorbance of monomer or shielding by the monomer solution, and a considerable amount of UV light does not reach the membrane. When UV light passes through to the membrane using the dipping technique, pore enlargement and a loss in protein rejection is observed because the UV light is not absorbed by the monomer solution as in the immersion technique. UV light at a wavelength of 254 nm has high energy capable of enlarging and damaging the pores, and thereby rendering the membrane useless. Therefore, a technique is required that will use less monomer and will allow a higher intensity, but lower energy UV light to reach the membrane, particularly because high intensity lower energy UV light optimizes the surface chain density and chain length for maximizing membrane permeability and retention properties, while reducing non- fouling characteristics.

[00011] U.S. Patent No. 6,852,769 to Belfort et al. discloses an ultrafiltration membrane modified to exhibit low protein fouling and yet maintains a greater fraction of the original membrane permeability and retention properties after modification. This is achieved by grafting monomer onto the surface of a highly photoactive membrane such as polyethersulfone, via the process of dipping the polymeric membrane into a solution containing one or more monomers and a chain transfer agent, removing the membrane from the solution, securing the membrane inside of a quartz vessel contained within another vessel of liquid filter, and irradiating the membrane with a UV light at a wavelength between the range of 280 nm and 300 nm. High density grafting and shorter grafted monomer chain length result in low protein fouling and retention of permeability.

[00012] U.S. Patent Publication No. 2006/0076288 discloses an improved efficient and effective method of manufacturing hydrophilic polyethersulfone (PES) membrane suitable for commercial applications.

[00013] As mentioned above, PES membranes are naturally hydrophobic. Most membrane applications require the use of hydrophilic membranes. Several different methods are known to transform hydrophobic PES membranes into hydrophilic PES membranes (to perform membrane hydrophilization). Some of these methods are complicated and expensive, while others fail to provide high purity membrane (for example, the membranes could contain the remains of hazardous or toxic monomers, used for hydrophilic coating).

[00014] Several different prior known methods of PES membrane hydrophilization are presented in the patent and scientific literature. In one known prior method, the hydrophilization of PES membrane was accomplished by coating the hydrophobic membrane with a hydrophilic polymer. In order to provide the desirable permanent attachment of the hydrophilic polymer to the membrane, a hydrophilic coating layer was usually subjected to a cross-linking reaction or a coating polymer was grafted to the surface of the hydrophobic PES membrane.

[00015] This approach is discussed in Chen et al., "Surface Modification of

Poly(ether sulfone) Ultrafiltraton Membranes by Low-Temperature Plasma- Induced Graft Polymerization," JAppl Polymer Sci, 72:1699-1711 (1999), which describes the hydrophilization of PES membrane by a grafting reaction. In this process, hydrophilic PES membrane was submitted to low-temperature helium plasma treatment followed by the grafting of hydrophilic monomer N vinyl-2- pyrrolidone onto the membrane surface.

[00016] The present invention is directed to overcoming these and other deficiencies in the art.

SUMMARY OF THE INVENTION

[00017] The present invention relates to a method of screening forms of monomers for effects of their polymers on a filter. This involves providing a multiple well filter, applying a monomer solution to one or more wells of the filter. The monomer is polymerized to produce a polymer-modified filter. The polymer-modified filter's performance is evaluated, and the performance of the polymer-modified filter is compared to the performance of the filter to determine the effect that polymerizing the monomer has on the performance of the filter. [00018] The present invention also relates to a method of producing a polymer-modified, multiple well filter. This involves providing a multiple well filter, applying a monomer solution to one or more wells of the multiple well filter, and polymerizing the monomer to produce a polymer-modified filter.

[00019] Another aspect of the present invention relates to an apparatus for screening forms of monomers for effects of their polymers on a filter. The apparatus includes a multiple well filter, a housing surrounding the multiple well filter having a radiation transparent cover, and a vacuum source operably coupled to the housing.

[00020] The present invention also relates to a product which includes a hydrophobic monomer polymerized to a polyethersulfone. The monomer can be hexyl methacrylate, 2-ethylhexyl methacrylate, diacetone acrylamide, isobornyl methacrylate, 4-acryloylmorpholine, JV-vinylcaprolactam, ethylene glycol phenyl ether methacrylate, styrene, or mixtures thereof.

[00021] The present invention also relates to a product which includes a hydrophilic monomer polymerized to a polyethersulfone. The monomer can be hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, 2- (diethylamino) ethyl methacrylate, iV-isopropylacrylamide, or mixtures thereof.

[00022] The present invention also relates to a product which includes a charged monomer polymerized to a polyethersulfone. The monomer can be [3- (methacryloylamino)propyl] dimethyl(3 -sulfopropyl)ammonium hydroxide inner salt, [2-(methacryloyloxy)ethyl] dimethyl-(3 -sulfopropyl)ammonium hydroxide, [3-(methacryloylamino)propyl]trimethylammonium chloride, [2- (methyacryloyloxy)ethyl]triethylammonium methyl sulfate, or mixtures thereof.

[00023] The present invention also relates to a product which includes a monomer polymerized to a polyethersulfone. The monomer is di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, or mixtures thereof. [00024] The present invention also relates to a method of producing a modified polyethersulfone. This involves providing a polyethersulfone and polymerizing to the polyethersulfone a hydrophobic monomer, a hydrophilic monomer, a charged monomer, or a monomer selected from di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, or mixtures thereof, as described above.

[00025] A fast, efficient and reproducible high throughput platform (HTP) approach is proposed to rapidly identify optimal surface or functional characteristics. Similar but different combinatorial approaches have been successfully used in chemistry and biology. It provides a basis for understanding mechanism of action to gain an understanding for future design of surfaces for membrane and other separations, and to match polymeric surfaces with particular applications. Thus using the invention one can customize surfaces for a specific need or objective.

[00026] This approach allows the facile modification of commercial PES membranes, combining the HTP approach together with a polymerization method. The method of the present invention is inexpensive, fast, simple, reproducible, and scalable. It can quickly produce large libraries of candidate surfaces from a library of monomers, and can quickly identify the surfaces having the surface or functional characteristics that optimize filtration of a specific feed stream. The HT approach can also optimize polymerizing and filtration conditions.

[00027] It is known that the continuous methods of membrane treatment are preferable for manufacturing conditions, because the continuous methods of membrane treatment are more economical and provide better uniformity of produced membrane than batch methods. The invention can be integrated into a continuous polymer and membrane production method. BRIEF DESCRIPTION OF THE DRAWINGS

[00028] Figures IA-B are schematic drawings of apparatus in accordance with the present invention.

[00029] Figure 2A-B shows the filtration assay data for natural organic matter (NOM) (Figure 2A) and bovine serum albumin (BSA) (Figure 2B) plotted in terms of a fouling index (y-axis) versus the membrane resistance increase after modification, R_mod, relative to the resistance of the as-received membrane, R_AR, washed with water only (x-axis). The fouling index is calculated as the resistance increase of grafted membranes caused by fouling {R_fouled R_mod) normalized by that of ungrafted membrane control,R_fouled R_control, (y-axis). The control is the as- received membrane treated with either water or ethanol, depending on which was used to dissolve the monomer. For monomers dissolved in water, R_control is the same as R_AR. It is desirable for the membrane resistance after modification to be near that of the as-received membrane (R_mod R_AR), although a higher resistance may be favorable when it correlates with increasing rejection. It is desirable for the increase in resistance after fouling to be lower for the modified membrane than the control, corresponding to y-axis values <1. The arrow indicates the desired direction.

DETAILED DESCRIPTION OF THE INVENTION

[00030] The present invention relates to a method of screening forms of monomers for effects of their polymers on a filter. This involves providing a multiple well filter, applying a monomer solution to one or more wells of the filter. The monomer is polymerized to produce a polymer-modified filter. The polymer-modified filter's performance is evaluated, and the performance of the polymer-modified filter is compared to the performance of the filter to determine the effect that polymerizing the monomer has on the performance of the filter.

[00031] The present invention also relates to a method of producing a polymer-modified, multiple well filter. This involves providing a multiple well filter, applying a monomer solution to one or more wells of the multiple well filter, and polymerizing the monomer to produce a polymer-modified filter. [00032] One embodiment of the present invention relates to a method of screening forms of monomers where different forms of monomers are applied to different wells of the filter to screen, in the different wells, for the effect that polymerizing the different forms of monomers has on the performance of the filter.

[00033] According to another embodiment, a library of different monomer forms are each applied to a separate well of the filter and then subjected to polymerization, evaluation, and comparison.

[00034] According to one embodiment, the polymerizing may be carried out at subatmospheric or atmospheric pressure, with exposure to radiation, preferably ultraviolet radiation, or exposure to plasma treatment.

[00035] As used herein, the term "radiation induced polymerization" refers to a polymerization reaction initiated by exposure to radiant energy rather than by chemical catalysts. For example, radiation-induced graft polymerization is a technique by which a substrate polymer is irradiated to form radicals and a polymerizable monomer is grafted onto the substrate at the radical sites. Since functional radicals can be introduced into various shapes of high-molecular weight compounds, radiation-induced graft polymerization is gaining popularity as a process for producing materials having a separating capability.

[00036] The conditions for polymerizing carried out with exposure to radiation may include monomer concentration, time of polymerizing, radiation frequency, and/or radiation intensity.

[00037] Plasma-induced polymerization is described in Lewis et al.,

"Inorganic Surface Nano structuring by Atmospheric Pressure Plasma-Induced Graft Polymerization," Langmuir 23(21): 10756-64 (2007), which is hereby incorporated by reference in its entirety. For example, plasma-induced graft polymerization is a surface modification approach in which plasma is used to activate the surface and monomer in the liquid phase is sequentially grafted to the initiation sites via a free radical grafting mechanism. This allows the engineering of a grafted polymer phase characterized by a high surface density of polymer chains that are initiated and polymerized directly from the substrate surface, thus minimizing polydisperse chain growth and improving stability under chemical, thermal, and shear stresses.

[00038] The conditions for polymerizing carried out with exposure to plasma treatment may include gas, RF power, plasma treatment time, monomer concentration, and temperature.

[00039] Favorable conditions for atmospheric pressure plasma include gas

(hydrogen, helium as single gases or as mixtures), RF power of 13.56 MHz (standard plasma frequency; voltage varies from 20-60 W), plasma treatment time (typically 5-40 s), monomer concentration (0-50%), and temperature (atmospheric to 80 °C).

[00040] As used herein, the term "polymerized" or "polymerization" encompass any process that results in the conversion of small molecular monomers into larger molecules consisting of repeated units (e.g., graft polymerization). Typically, polymerization involves chemical crosslinking of molecular monomers.

[00041] The different monomer forms may differ by monomer type, by monomer concentration, and/or as a result of conditions for said polymerizing.

[00042] The monomer may be a hydrophobic monomer selected from the group consisting of hexyl methacrylate, 2-ethylhexyl methacrylate, diacetone acrylamide, isobornyl methacrylate, 4-acryloylmorpholine, N-vinylcaprolactam, ethylene glycol phenyl ether methacrylate, styrene, and mixtures thereof.

[00043] The monomer may be a hydrophilic monomer selected from the group consisting of hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl methacrylate, N-isopropylacrylamide, and mixtures thereof.

[00044] The monomer may be a charged monomer selected from the group consisting of [3 -(methacryloylamino)propyl] dimethyl(3 -sulfopropyl)ammonium hydroxide inner salt, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide, [3-(methacryloylamino)propyl]trimethylammonium chloride, [2-(methyacryloyloxy)ethyl]triethylammonium methyl sulfate, and mixtures thereof.

[00045] The monomer may be selected from the group consisting of di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, and mixtures thereof.

[00046] Evaluation of the polymer-modified filter's performance may include applying a material to be filtered to the polymer-modified filter and measuring permeation flux and/or measuring volume of permeate produced over a specified time period and solute concentration of permeate solutions.

[00047] The filter may be made of a membrane selected from the group consisting of poly(aryl sulfones), polypropylene, polyethylene, polyethersulfone, polyvinylidene fluoride, polyacrilonitrile, and polyamide.

[00048] It is preferable that the filter is made of a membrane comprising polyethersulfone .

[00049] Polyethersulfone (PES) is widely used for filtration (i.e. designed to remove molecules, colloids, particulates, or some combination thereof) and in the preparation of modified membranes. The modified membranes and membrane compositions of the present invention can be used for the membrane purposes listed above. Further, the membranes of the present invention can be utilized to separate other materials besides proteins, such as alcohols, sugars, humic and fulvic acids, and other components of natural organic matter.

[00050] Polyethersulfones are highly resilient polymer thermoplastic plastics. Materials made of polyethersulfones are transparent or slightly transparent (high light transmission and refractive index), resistant to hydrolysis, and provide excellent chemical resistance to mineral lubricants, aliphatic hydrocarbons, acids, and alkalis.

[00051] The general formula of a polyethersulfone is:

[00052] The thermoplastic polyethersulfone has a melting range or glass transition temperature of approximately 22O°C and can be processed to form a finished product with up to 30% inorganic fillers, fiberglass or carbon fibers in an extrusion (extruded profiles) or injection moulding process. Due to their optimum electrical insulating properties, polyethersulfones have applications in the electronics and automobile industries. Polyethersulfones are also used in the medical sector, the food and beverage sector (membrane technology), as well as in aircraft cabins.

[00053] Polyethersulfone allows easy manufacturing of membranes, with reproducible properties and controllable size of pores. Such membranes can be used in applications like hemodialysis, water purification, waste water recovery, food and beverage processing, and gas separation.

[00054] The high hydrolysis stability of polyethersulfone allows its use in medical applications requiring autoclave and steam sterilization. However, it has low resistance to some solvents and undergoes weathering; however the weathering instability can be offset by adding materials into the polymer.

[00055] Polyethersulfone polymers are commonly used by many manufacturers to produce ultrafiltration membranes. In many applications, these polyethersulfone membranes, which are intrinsically photoactive, and are relatively hydrophobic in character, are very susceptible to membrane fouling and plugging by dissolved solutes such as proteins or suspended colloids such as latex paint particles and natural organic matter. Adsorption of such solutes in the membrane pores can impede and constrict the flow through the membrane and result in diminished performance. By modifying these polyethersulfone membranes, using the present invention, solute-membrane interactions will be reduced and this results in improved long-term performance. Thus, for example, recovery and purification of valuable proteins and water purification using ultrafiltration would be more efficient when using modified polyethersulfone membranes of the present invention rather than unmodified commercially available polyethersulfone membranes.

[00056] Another aspect of the present invention relates to an apparatus for screening forms of monomers for effects of their polymers on a filter. This involves a multiple well filter, a housing surrounding the multiple well filter having a cover to define a chamber, and a vacuum source operably coupled to the housing.

[00057] The apparatus additionally includes a source of ultraviolet radiation positioned to apply ultraviolet radiation through the cover (which is radiation transparent), and a dispensing device to apply monomer solution to individual wells. Instead of a source of ultraviolet radiation, the apparatus can include a system for producing a low temperature or atmospheric pressure plasma. That system is positioned to apply the plasma within the chamber and onto the multiple well filter.

[00058] Irradiation with nonionizing ultraviolet light can be accomplished using traditional, high, low and medium pressure mercury arc lamps. In addition, such irradiation can be achieved using xenon and carbon arc lamps. Further, other UV sources, such as lasers, may also be employed by the present invention. Other examples of lamps which can be used are "electrodeless" lamps, such as microwave driven lamps. Such lamps may be filled with only mercury or may contain mercury which is "doped" with other elements to modify its emission spectrum. Optical filters to control the irradiation spectrum can also be used.

[00059] Figure IA shows a schematic drawing of one embodiment of an apparatus in accordance with the present invention. In particular, it illustrates a system for carrying out a method for modifying membranes and evaluating filtration performance using a high throughput platform with photo-induced graft polymerization (HTP-PGP). The apparatus of Figure 1 shows monomer solution 2 added to 96-well filter 4. Filter 4 is then covered and sealed with quartz plate 6 and placed under vent 8 in glass container 10. Oxygen is then removed via displacement by N₂ gas 12. Filter 4 is placed in UV irradiator 14, which is connected to power supply 16. Filter 4 is irradiated with a UV lamp 18 with filter 20 restricting the wavelengths to between 280 and 315 nm for poly(ether sulfone) synthetic membrane exposed for a specified time, and then placed on vacuum manifold 22 connected to vacuum pump 24 to conduct filtration with protein containing feed.

[00060] Figure IB shows a schematic drawing of another embodiment of an apparatus in accordance with the present invention. In particular, it illustrates a system for carrying out a method for modifying membranes and evaluating filtration performance using a high throughput platform with plasma-induced graft polymerization. The apparatus of Figure IB shows monomer solution 102 added to 96-well filter 104. Filter 104 is then placed in glove box 140 with plasma dispenser 150 so that plasma dispenser 150 is positioned to move across filter 104. Glove box 140 is provided with atmospheric blanket gas port 142 and vacuum purge port 144. Plasma dispenser 150 is connected to RF generator 152. Plasma reagent port 154 and carrier gas port 156, which are provided with controllers 158 and 160, respectively, are coupled through control valve 162 to plasma dispenser 150. Filter 104 is then placed on vacuum manifold 122 connected to vacuum pump 124 to conduct filtration with protein containing feed.

[00061] The present invention also relates to a product which includes a hydrophobic, hydrophilic, charged, or monomer selected from the groups described above polymerized to a polyethersulfone. The product may be in the form of a filter.

[00062] A filter membrane may be used in the present invention. This is particularly suitable for a "flow through" assay. The term "filter membrane" is meant to include porous materials designated for ultrafiltration having pore sizes ranging from about 5 nm to about 0.1 μm, and those designated for micro filtration having pore sizes ranging from about 0.1 μm to about 10 μm., which allows an aqueous medium to flow therethrough. The pore size has an important impact on the performance of the device. [00063] The present invention also relates to a method of producing a modified polyethersulfone. This involves providing a polyethersulfone and polymerizing to the polyethersulfone a monomer, such as hydrophobic, hydrophilic, or charged monomers. Alternatively, a monomer, such as di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, or mixtures thereof, as described above, can be used.

[00064] In addition to a polyethersulfone, other polymers may be provided to polymerize. These include polymers of: hexyl methacrylate, 2-ethylhexyl methacrylate, diacetone acrylamide, isobornyl methacrylate, A- acryloylmorpholine, JV-vinylcaprolactam, ethylene glycol phenyl ether methacrylate, styrene, hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl methacrylate, iV-isopropylacrylamide, [3- (methacryloylamino)propyl] dimethyl(3 -sulfopropyl)ammonium hydroxide inner salt, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide, [3 -(methacryloylamino)propyl]trimethylammonium chloride, [2-

(methyacryloyloxy)ethyl]triethylammonium methyl sulfate, di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, and mixtures thereof.

EXAMPLES

[00065] The following examples are provided to illustrate embodiments of the present invention but are by no means intended to limit its scope.

Example 1- Membrane

[00066] Standard 96-well filters donated by Seahorse Labware (Chicopee,

MA) were applied to HTP-photo-induced graft polymerization (PGP) experiments. 100 kDa cut-off PES membrane coupons are mounted by the manufacturer on the bottom of each well. The effective area of each membrane coupon is 19.35 mm², and the maximum operating volume of each well is 400 μL. The hydraulic resistance of the 96 membranes of the filter has a very low degree of variability, with values ranging from 0.126x10 to 0.147x10 m Pa-s/kg and a ratio of the standard deviation to the mean of 4.0%. The housing of the filters is made of a high grade of polypropylene to ensure a high level of chemical compatibility to a wide range of solutions. Prior to use, the filters were washed several times with deionized (DI) water and soaked in DI water overnight to remove surfactant from membrane coupons.

Example 2- Monomers

[00067] All the monomers were purchased from Sigma- Aldrich (Saint

Louis, MO). A library of 66 commercial vinyl monomers (including acrylic acid (AA), 2-acrylamidoglycolic acid (AAG), 3-sulfopropyl methacrylate (SPMA), and 2-acrylamido-2-methyl-l-propanesulfonic acid (AMPS)) was evaluated. The name, structure, and formula weight (FW) of these monomers are shown infra in Tables 2A-H. These monomers were either dissolved in reagent grade water (number 32, 33, 34, 35, 36, 39, 40, 41, 43, 44, 45, 46, 48, 49, 50, 51, 53, 54, 55, 57, 58, 59, 60, 61, 62, 63) or ethanol (the rest of the monomers) depending on their solubility. For all the 66 monomers, a concentration of 0.2 mol/L and UV irradiation time of 30 seconds were applied for graft polymerization. All the monomers were used as-received without further purification.

Example 3- BSA and Lysozyme Foulants

[00068] Two proteins, bovine serum albumin (BSA, 67 kDa, pi 4.7) and lysozyme (Lys, 14.7 kDa, pi 11.0), were applied as the predictors of membrane fouling potential to identify the foulant-specifϊc (or feed-specific) surfaces. Solutions were prepared by dissolving single protein into phosphate buffered saline (PBS) solution to yield a concentration of 1 mg/mL. PBS buffer solution was prepared by dissolving one PBS tablet in 200 mL DI water. The resulting solution contained 10 mM phosphate buffer, 2.7 mM potassium chloride, and 137 mM sodium chloride with pH 7.4 at 25 °C. BSA, lysozyme and PBS tablets were purchased from Sigma-Aldrich (Saint Louis, MO).

Example 4- Humic Acid Foulants

[00069] A soil humic acid (Elloit Humic Acid, EHA) from IHSS

(International Humic Substance Society) was selected as a model natural organic matter (NOM) because of its high fouling potential. An NOM concentration of 50 mg/L (as dissolved organic carbon, DOC) was used. The solution was adjusted to pH 7 using HCl and NaOH solutions and 0.1 M ionic strength by adding solid NaCl. The NOM concentration and solution ionic strength were higher than typically found in natural systems to accelerate fouling.

Example 5- Preparation of Modified Membranes Using High Throughput Photo Graft Polymerization (HTP-PGP) Methods

[00070] The membranes on the 96-well filters were modified using the

UV-induced graft polymerization method, with the mechanisms described in previous publications (U.S. Patent No. 5,468,390 to Crivello et al; Yamagishi et al., Development of a Novel Photochemical Technique for Modifying Poly(arylsulfone) Ultrafiltration Membranes," J Membrane Science 105(3):237- 247 (1995); Taniguchi et al., "UV-Assisted Graft Polymerization of Synthetic Membranes: Mechanistic Studies." Chemistry of Materials 15(20): 3805-3812 (2003), which are hereby incorporated by reference in their entirety). A UV curing system (F300S, Fushion UV Systems, Inc. Gaithersburg, MD) contained an electrodeless microwave lamp (~ 7% of the energy was at < 280 nm) was used. A bandpass UV filter (UG-11, Newport Corporation, Franklin, MA) was placed between the filter and UV lamp to reduce the energy at < 280 nm further down to < 1%.

[00071] The membrane modification experiments consist of the following steps. First, the membrane hydraulic permeability was measured with DI water after soaking in DI overnight. The membranes were then modified by adding monomer solution (200 μL) to each well, shaking filters on an orbital shaker at 100 rpm for 1 hr, purging it with N₂ for 15 minutes to reduce the oxygen concentration, irradiating filters in a UV chamber for a specified time. After modification, the filters were washed by shaking in water for 1 hr.

[00072] Each 96-well filter allowed evaluation of 22 monomers with 4 replicates for each monomer, and 8 controls: 4 membrane coupons were treated with ethanol without UV irradiation to serve as a control for membranes grafted with the monomers dissolved in ethanol, and the remaining 4 wells were used as- received to serve as a control for the membranes grafted with monomers dissolved in DI water.

Example 6- Evaluation of Modified Membranes by Static Adsorption

[00073] The fouling potential of modified and control (no-modification) membranes was evaluated using static adsorption experiments, after the photo- induced graft polymerization. Water permeability reduction after adsorption was measured as a criterion to evaluate monomer capability to reduce fouling.

[00074] In this method, 300 μL of foulant solution was added to each well, and the filter was sealed with a piece of adhesive film to eliminate evaporation. The filter was then placed on a shaker (as above) for 44 hrs. After equilibration, the wells were gently emptied, and DI flux was measured. The membrane resistance was calculated using flux values. The resistance increase after adsorption of the modified membranes was compared with that of control membranes to evaluate the ability of the monomers on mitigating fouling.

Example 7- Evaluation of Modified Membranes by Filtration

[00075] The fouling potential of modified and control (no-modification) membranes was evaluated using filtration experiments, after the photo-induced graft polymerization. Water permeability reduction after filtration was measured as a criterion to evaluate monomer capability to reduce fouling.

[00076] In this method, the flux and fouling behavior of the 96 membrane coupons was measured simultaneously by mounting the filter on a vacuum manifold (Pall Corporation, East Hills, NY). A constant transmembrane pressure (TMP) of 9.8 psi was provided by a vacuum pump. First, water and then PBS solution flux were measured, and then 300 μL of foulant solution was added to each well. A vacuum was then applied for 4 min., after which the wells were gently emptied and refilled with PBS solution. The PBS flux was measured again, followed by a DI water measurement.

[00077] During filtration, a 96-well receiver filter was placed under the 96- well filter. The permeate from each membrane was collected into a corresponding well in the receiver filter, and was analyzed for solute concentration and volume (as described below) to calculate the rejection and flux properties of each membrane. The receiver filter was replaced by an empty receiver filter every time the wells of the membrane filter were refilled.

Example 8- Analytical Method

[00078] A Microplate Spectrophotometer (PowerWave XS, BioTek

Instruments Inc., Winooski, VT), which allows 200-999 nm wavelength selection in 1 nm increments, was used to measure the volumes of solutions in the wells of the receiver filters. The 96-well receiver filters are made of acrylic, which is UV transparent and allows for the permeate sample analysis by light absorbance in both UV and near infrared regions. The volumes were measured at 977 nm. At this light wavelength, water has a natural absorbance peak while other chemicals do not. Flux was calculated with equation: J = V I At, where V is the permeate volume, A is the membrane area, and t is the filtration time. The hydrodynamic resistances for the membranes, R_M, R_M,,_PBS, and Rp represent membrane DI water resistance before filtration, PBS solution resistance before filtration, and DI water resistance after protein solution filtration. The resistance was calculated from permeation using equation R = ΔP I J, where ΔP is the transmembrane pressure.

Example 9- Evaluation of the 66 Monomers

[00079] A suite of 66 commercially-available monomers were employed for membrane surface modification by the HTP-PGP method of the present invention. BSA and lysozyme in PBS (phosphate buffered saline solution) and Elliot Humic Acid (NOM) were selected as feed solutions for the evaluation of membrane adsorption and filtration. The properties of the foulants are significantly different: BSA is a large flexible protein (MW = 67 kDa, pi = 4.7), which is negatively charged under experimental conditions. Lysozyme is a small, rigid protein (MW = 14.7 kDa, pi = 11), which is positively charged under experimental conditions. Elliot humic acid is a flexible natural mixture of organic acids which are negatively charged under experimental conditions. [00080] The new monomers can be classified into the following groups: methacrylates having aliphatic side chains; hetero ring compounds; aromatic; hydroxy; PEG, poly(ethylene glycol); acidic, both strong (sulfonic) and weak (carboxylic); amine; basic and zwitterionic.

[00081] Water flux was measured after static adsorption of BSA and lysozyme on modified membrane surfaces. The membrane resistance was calculated using the flux values before and after membrane static adsorption. A new method of data analysis included calculating the following parameters: (R_mod/R_control) represents the factor by which membrane resistance increase after modification; (R_fouled-R_mod) represents the increase in resistance of grafted membranes after protein adsorption (same as apparent total fouling, R_τ); (R_fouled-R_mod)/(R_fouled-R_control) represents the increase in resistance of grafted membranes after protein adsorption normalized by that of ungrafted membrane control (either ethanol or water). The resistance increase was rated into 7 classes as shown by the criteria in Table 1 for fast evaluation of the adsorption and filtration performance. The symbol "--- " means the membrane has highest resistance after surface modification, which indicates the surface chemistry is not good for membrane filtration; whereas the symbol "++++" means the membrane has lowest resistance after surface modification, which indicates the surface chemistry is good for membrane filtration.

[00082] Flux of foulant-free solution (either water or PBS buffer) was measured after filtration of BSA and lysozyme solutions by modified membrane surfaces. The membrane resistance was calculated using the flux values before and after filtration of BSA and lysozyme solutions. A new method of data analysis included calculating the following parameters: (R_mod/R_control) represents the factor by which membrane resistance increases after modification; (R_fouled-R_mod) represents the increase in resistance of grafted membranes after protein adsorption (same as apparent total fouling, R_τ); (R_fouled-R_mod)/(R_fouled-R_control) represents the increase in resistance of grafted membranes after protein adsorption normalized by that of ungrafted membrane control (either ethanol or water). The resistance increase was rated into 7 classes as shown by the criteria in Table 1 for fast evaluation of the adsorption and filtration performance. The symbol "— " means the membrane has highest resistance after surface modification, which indicates the surface chemistry is not good for membrane filtration; whereas the symbol "++++" means the membrane has lowest resistance after surface modification, which indicates the surface chemistry is good for membrane filtration.

[00083] Flux of foulant-free solution (either water or PBS buffer) was measured after static adsorption of NOM by membrane surfaces. The membrane resistance was calculated using the flux values before and after membrane static adsorption. Data analysis included calculating the following parameters: A new method of data analysis included calculating the following parameters: (R_mod/R_control) represents the factor by which membrane resistance increase after modification; (R_fouled-R_mod) represents the increase in resistance of grafted membranes after NOM adsorption (same as apparent total fouling, R_T); (R_fouled-R_mod)/(R_fouled-R_control) represents the increase in resistance of grafted membranes after NOM adsorption normalized by that of ungrafted membrane control. A higher (R_fouled-R_mod)/(R_fouled-R_control) value means the membrane exhibits a higher NOM adsorption fouling potential after surface modification, which indicates the surface chemistry of the modified membrane is not favorable for NOM. Figure 2 A shows the (R_fouled-R_mod)/(R_fouled-R_control) versus (R_mod/R_control) for the evaluated monomers. The arrow indicates the desired direction for modified membranes.

[00084] Flux of foulant-free solution (either water or PBS buffer) was measured after filtration of NOM solution by modified membrane surfaces. The membrane resistance was calculated using the flux values before and after filtration of NOM solution. A new method of data analysis included calculating the following parameters: (R_mod/R_control) represents the factor by which membrane resistance increases after modification; (R_fouled-R_mod) represents the increase in resistance of grafted membranes after NOM adsorption (same as apparent total fouling, R_τ); (R_fouled-R_mod)/(R_fouled--R_control) represents the increase in resistance of grafted membranes after NOM adsorption normalized by that of ungrafted membrane control. The resistance increase was rated into 7 classes as shown by the criteria in Table 1 for fast evaluation of the adsorption and filtration performance. The symbol " — " means the membrane has highest resistance after surface modification, which indicates the surface chemistry is not good for membrane filtration; whereas the symbol "++++" means the membrane has lowest resistance after surface modification, which indicates the surface chemistry is good for membrane filtration.

[00085] Figure 2A-B shows the filtration assay data for natural organic matter (NOM) (Figure 2A) and bovine serum albumin (BSA) (Figure 2B) plotted in terms of a fouling index (y-axis) versus the membrane resistance after modification, R_mod, relative to the resistance of the as-received membrane, R_AR, washed with water only (x-axis). The fouling index is calculated as the resistance increase of grafted membranes caused by fouling (R_fouled - R_mod) normalized by that of ungrafted membrane control, R_fouled - R_control, (y-axis). The control is the as-received membrane treated with either water or ethanol, depending on which was used to dissolve the monomer. For monomers dissolved in water, R_controi is the same as R_AR It is desirable for the membrane resistance after modification to be near that of the as-received membrane (R_mod ≤ R_AR), although a higher resistance may be favorable when it correlates with increasing rejection. It is desirable for the increase in resistance after fouling to be lower for the modified membrane than the control, corresponding to y-axis values < 1. The arrow indicates the desired direction.

[00086] The performance of monomers evaluated by resistance increase after static adsorption by grafted membranes is set forth in Table 2, which provides a summary of BSA, lysozyme, and NOM results, and name, structure, and FW of the monomers. Ratings were based on the criteria in Table 1. A superscript "a" means that the monomer was dissolved in ethanol; ND means not determined.

[00087] The results for NOM are generally consistent with the following features of surfaces exhibiting low protein adsorption: (i) hydrophilic (wettable); (ii) presence of hydrogen bond acceptors, (iii) lack of hydrogen bond donors, (iv) neutral net electrical charge (Chapman et al., "Surveying for Surfaces that Resist the Adsorption of Proteins," JAm Chem Soc 122:8303-8304 (2000); Ostuni et al., "A Survey of Structure-Property Relationships of Surfaces that Resist the Adsorption of Protein," Langmuir 17:5605-5620 (2001), which are hereby incorporated by reference in their entirety. However, due to the complexity of NOM as compared to proteins, some exceptions were observed.

[00088] It was found that for NOM, the membrane surfaces grafted with the zwitterionic monomers had great potential to resist fouling, possibly due to the net electrical neutrality of the surfaces. The basic monomers also performed well. Membranes modified with high molecular weight PEG monomers decreased flux decline after NOM adsorption, likely because these PEGs are very hydrophilic, and as the repeat unit of ethylene glycol increases, the hydrophilicity increases.

Membrane resistance after grafting and subsequent NOM adsorption increased for most of the hydrophobic aliphatic methacrylates, aromatic and hetero ring group monomers. The hydroxyl monomers and acid monomers performed poorly, possibly because most of these monomers have hydrogen bond donor groups, such as OH, COOH, SO₃H, and NH₂. However, it was also observed that amines grafted membrane surfaces decreased membrane flux decline after adsorption although they have hydrogen bond donor, NH and NH₂ groups.

[00089] The results are generally consistent with the following features of surfaces exhibiting low protein adsorption: (i) hydrophilic (wettable); (ii) presence of hydrogen bond acceptors; (iii) lack of hydrogen bond donors; (iv) neutral net electrical charge (Chapman et al., "Surveying for Surfaces that Resist the Adsorption of Proteins," J Am Chem Soc 122(34):8303 (2000); Holmlin et al., "Zwitterionic SAMs that Resist Nonspecific Adsorption of Protein from Aqueous Buffer," Langmuir 17(9):2841-2850 (2001); Ostuni et al., "A Survey of Structure- property Relationships of Surfaces that Resist the Adsorption of Protein,"

Langmuir 17(18):5605-5620 (2001), which are hereby incorporated by reference in their entirety). [00090] From these results, it was found that the membrane surfaces grafted by the zwitterionic monomers of 59 and 60 had great potential at resisting fouling of both proteins, due to the net electrical neutrality of the surfaces. Membranes modified with high molecular weight poly(ethylene glycol) (PEG) monomers (monomers 31, 32, 33, 34 and 35) decrease flux decline after adsorption of both proteins, because these PEGs are very hydrophilic, and as the repeat unit of ethylene glycol increases, the hydrophilicity increases. The hydroxyl monomers and acid monomers performed poorly, because most of these monomers have hydrogen bond donor groups, such as OH, COOH, SO₃H, and NH₂. For most of the hydrophobic monomers, the membrane resistance increased after the adsorption of the proteins.

[00091] However, it was also observed that the positively charged monomers (61-63) grafted membrane surfaces decreased membrane flux decline after adsorption of one or both proteins. In the experiments, BSA was negatively charged, and lysozyme was positively charged. Results show that the surfaces grafted with monomers 61-63 were more favorable for lysozyme, which can be attributed to electrostatic repulsion interaction of positively charged lysozyme with positively charged surfaces.

[00092] Amine monomers tended to produce foulant-specific surfaces. Except for monomer 55, which works for both BSA and lysozyme, all other monomers work for only one of the two proteins. Hetero ring group monomers worked better for lysozyme than BSA.

[00093] Table 2 shows that some monomers are feed-specific for lysozyme, such as monomers 6, 38, 39, 26, 37, 24 and 56; and some monomers are feed-specific for BSA, such as 7, 15, 18, 29. This finding is attributed to the difference between lysozyme and BSA based on structure, conformation, molecular weight, and isoelectronic point. However, it is possible to obtain a low protein fouling surface or a low membrane resistance surface for both BSA and lysozyme by modification of the membrane with zwitterionic monomers of 59, 60, high molecular weight PEG monomers 33, 34, 35, or amine monomer 55. Example 10 - Evaluation of Previously Studied Monomers According to New Rating Criteria

[00094] Criteria was previously studied in large scale (not HTP-PGP) by

Taniguchi et al., "UV-Assisted Graft Polymerization of Synthetic Membranes: Mechanistic Studies," Chem Mater 15:3805-3812 (2003) and Taniguchi et al., "Low Fouling Synthetic Membranes by UV-Assisted Graft Polymerization: Monomer Selection to Mitigate Fouling by Natural Organic Matter," JMembr Sci 222:59-70 (2003), which are hereby incorporated by reference in their entirety.

[00095] The results of six monomers were reanalyzed, and monomers were rated using the criteria in Table 1, with the rating shown in Table 3. As mentioned earlier, AA, AAG, SPMA, and AMPS were tested both as the six validation monomers and in the library of 66 monomers. The results of these monomers in the two sets of experiments were in a good agreement. Table 3 shows that at a concentration of 0.2 mol/L and a UV irradiation time of 30 seconds, the rating of AA was ( — ), and AAG, SPMA, and AMPS could not be determined due to the low permeability of the grafted membranes. In Table 2, the rating of AA (43) was also (— ); AAG (44) could not be determined; SPMA (46) was rated (-) for BSA and (— ) for Lys; and AMPS (48) could not be determined for BSA and rated ( — ) for Lys.

[00096] Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the claims which follow.

Claims

WHAT IS CLAIMED:

1. A method of screening forms of monomers for effects of their polymers on a filter, said method comprising: providing a multiple well filter; applying a monomer solution to one or more wells of the filter; polymerizing the monomer to produce a polymer-modified filter; evaluating the polymer-modified filter's performance; and comparing the performance of the polymer-modified filter to the performance of the filter without polymer modification to determine the effect that said polymerizing the monomer has on the performance of the filter.

2. The method of claim 1, wherein different forms of monomers are applied to different wells of the filter to screen, in the different wells, for the effect that said polymerizing the different forms of monomers has on the performance of the filter.

3. The method of claim 1 , wherein a library of different monomer forms are each applied to a separate well of the filter and then subjected to said polymerizing, evaluating, and comparing.

4. The method of claim 1 , wherein said polymerizing is carried out at subatmospheric pressure or atmospheric pressure.

5. The method of claim 1, wherein said polymerizing is carried out with exposure to radiation.

6. The method of claim 5, wherein said radiation is ultraviolet radiation.

7. The method of claim 1 , wherein said polymerizing is carried out with exposure to plasma treatment.

8. The method of claim 1 , wherein the monomer is a hydrophobic monomer selected from the group consisting of hexyl methacrylate, 2-ethylhexyl methacrylate, diacetone acrylamide, isobornyl methacrylate, A- acryloylmorpholine, N-vinylcaprolactam, ethylene glycol phenyl ether methacrylate, styrene, and mixtures thereof.

9. The method of claim 1 , wherein the monomer is a hydrophilic monomer selected from the group consisting of hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl methacrylate, N-isopropylacrylamide, and mixtures thereof.

10. The method of claim 1 , wherein the monomer is a charged monomer selected from the group consisting of [3- (methacryloylamino)propyl] dimethyl(3 -sulfopropyl)ammonium hydroxide inner salt, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, [3 -(methacryloylamino)propyl]trimethylammonium chloride, [2-(methyacryloyloxy)ethyl]triethylammonium methyl sulfate, and mixtures thereof.

11. The method of claim 1 , wherein the monomer is selected from the group consisting of di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, and mixtures thereof.

12. The method of claim 1 , wherein the different monomer forms differ by monomer type, by monomer concentration, and/or as a result of conditions for said polymerizing.

13. The method of claim 12, wherein said polymerizing is carried out with exposure to radiation and said conditions for said polymerizing are monomer concentration, time of said polymerizing, radiation frequency, and/or radiation intensity.

14. The method of claim 12, wherein said polymerizing is carried out with exposure to low temperature and atmospheric pressure plasma treatment and said conditions for said polymerizing are gas, RF power, plasma treatment time, monomer concentration, and temperature.

15. The method of claim 1, wherein said evaluating is carried out by applying a material to be filtered to the polymer-modified filter and measuring permeation flux and/or measuring volume of permeate produced over a specified time period and solute concentration of permeate solutions.

16. The method of claim 1 , wherein the filter is made of a membrane selected from the group consisting of poly(aryl sulfones), polypropylene, polyethylene, polyethersulfone, polyvinylidene fluoride, polyacrilonitrile, and polyamide.

17. The method of claim 16, wherein said filter is made of a membrane comprising polyethersulfone.

18. A method of producing a polymer-modified, multiple well filter, said method comprising: providing a multiple well filter; applying a monomer solution to one or more wells of the multiple well filter, and polymerizing the monomer to produce a polymer-modified filter.

19. The method of claim 18, wherein said polymerizing is carried out at subatmospheric pressure.

20. The method of claim 18, wherein said polymerizing is carried out with exposure to radiation.

21. The method of claim 20, wherein said radiation is ultraviolet radiation.

22. The method of claim 18, wherein the monomer is a hydrophobic monomer selected from the group consisting of hexyl methacrylate, 2-ethylhexyl methacrylate, diacetone acrylamide, isobornyl methacrylate, A- acryloylmorpholine, JV-vinylcaprolactam, ethylene glycol phenyl ether methacrylate, styrene, and mixtures thereof.

23. The method of claim 18, wherein the monomer is a hydrophilic monomer selected from the group consisting of hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino) ethyl methacrylate, iV-isopropylacrylamide, and mixtures thereof.

24. The method of claim 18, wherein the monomer is a charged monomer selected from the group consisting of [3- (methacryloylamino)propyl] dimethyl(3 -sulfopropyl)ammonium hydroxide inner salt, [2-(methacryloyloxy)ethyl] dimethyl-(3 -sulfopropyl)ammonium hydroxide, [3 -(methacryloylamino)propyl]trimethylammonium chloride, [2-(methyacryloyloxy)ethyl]triethylammonium methyl sulfate, and mixtures thereof.

25. The method of claim 18, wherein the monomer is selected from the group consisting of di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, and mixtures thereof.

26. The method of claim 18, wherein the filter is made of a membrane selected from the group consisting of poly(aryl sulfones), polypropylene, polyethylene, polyethersulfone, polyacrilonitrile, and polyvinylidene fluoride.

27. The method of claim 25, wherein said filter is made of a membrane comprising polyethersulfone.

28. An apparatus for screening forms of monomers for effects of their polymers on a filter, said apparatus comprising: a multiple well filter; a housing surrounding said multiple well filter and having a cover to define a chamber; and a vacuum source operably coupled to said housing.

29. The apparatus of claim 28 further comprising: a source of ultraviolet radiation positioned to apply ultraviolet radiation through said cover onto the multiple well filter.

30. The apparatus of claim 28 further comprising: a dispensing device to apply monomer solution to individual wells of said multiple well filter.

31. The apparatus of claim 28 further comprising: a system for producing a low temperature or atmospheric pressure plasma, said system being positioned to apply the plasma within the chamber and onto the multiple well filter.

32. A product comprising a hydrophobic monomer polymerized to a polyethersulfone, said monomer being selected from the group consisting of hexyl methacrylate, 2-ethylhexyl methacrylate, diacetone acrylamide, isobornyl methacrylate, 4-acryloylmorpholine, JV-vinylcaprolactam, ethylene glycol phenyl ether methacrylate, styrene, and mixtures thereof.

33. A filter comprising the product of claim 32.

34. A product comprising a hydrophilic monomer polymerized to a polyethersulfone, said monomer being selected from the group consisting of hydroxypropyl methacrylate, 2-(dimethylamino)ethyl methacrylate, 2- (diethylamino) ethyl methacrylate, iV-isopropylacrylamide, and mixtures thereof.

35. A filter comprising the product of claim 34.

36. A product comprising a charged monomer polymerized to a polyethersulfone, said monomer being selected from the group consisting of [3- (methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide inner salt, [2-(methacryloyloxy)ethyl] dimethyl-(3 -sulfopropyl)ammonium hydroxide, [3 -(methacryloylamino)propyl]trimethylammonium chloride, [2-(methyacryloyloxy)ethyl]triethylammonium methyl sulfate, and mixtures thereof.

37. A filter comprising the product of claim 36.

38. A product comprising a monomer polymerized to a polyethersulfone, said monomer being selected from the group consisting of di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, and mixtures thereof.

39. A filter comprising the product of claim 38.

40. A method of producing a modified polyethersulfone, said method comprising: providing a polyethersulfone and polymerizing to the polyethersulfone a hydrophobic monomer selected from the group consisting of hexyl methacrylate, 2-ethylhexyl methacrylate, diacetone acrylamide, isobornyl methacrylate, A- acryloylmorpholine, JV-vinylcaprolactam, ethylene glycol phenyl ether methacrylate, styrene, and mixtures thereof.

41. A method of producing a modified polyethersulfone, said method comprising: providing a polyethersulfone and polymerizing to the polyethersulfone a hydrophilic monomer selected from the group consisting of hydroxypropyl methacrylate, 2- (dimethylamino)ethyl methacrylate, 2-(diethylamino) ethyl methacrylate, N- isopropylacrylamide, and mixtures thereof.

42. A method of producing a modified polyethersulfone, said method comprising: providing a polyethersulfone and polymerizing to the polyethersulfone a charged monomer selected from the group consisting of [3-(methacryloylamino)propyl]dimethyl(3- sulfopropyl)ammonium hydroxide inner salt, [2-(methacryloyloxy)ethyl]dimethyl- (3 -sulfopropyl)ammonium hydroxide, [3 -

(methacryloylamino)propyl]trimethylammonium chloride, [2-(methyacryloyloxy)ethyl]triethylammonium methyl sulfate, and mixtures thereof.

43. A method of producing a modified polyethersulfone, said method comprising: providing a polyethersulfone and polymerizing to the polyethersulfone a monomer selected from the group consisting of di(ethylene glycol) methyl ether methacrylate, poly(ethylene glycol) methyl ether methacrylate, and mixtures thereof.