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  • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
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  • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
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  • C09D133/00—Coating compositions based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Coating compositions based on derivatives of such polymers
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  • C09D133/14—Homopolymers or copolymers of esters of esters containing halogen, nitrogen, sulfur or oxygen atoms in addition to the carboxy oxygen
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  • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
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  • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
  • C08J2333/04—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters
  • C08J2333/06—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers esters of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical
  • C08J2333/10—Homopolymers or copolymers of methacrylic acid esters
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  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
  • Y02A20/124—Water desalination
  • Y02A20/131—Reverse-osmosis

Definitions

• Nanofiltration (NF) membranes are defined by effective pore sizes ⁇ 1 nm. They are typically used for removing divalent salts from water and wastewater streams in
• polyamide selective layers also come with significant limitations inherent to their chemical structure, such as lack of fouling and chlorine resistance.
• zwitterions have attracted extensive research in the membrane field due to their
• ZACs Zwitterionic amphiphilic copolymers
• copolymers comprising pluralities of each of three types of monomeric units: hydrophobic monomeric units, zwitterionic monomeric units, and charged or ionizable monomeric units.
• the copolymers are linear, statistical, or random, or all of them.
• thin film composite membranes whose selective layer is comprised of these copolymers. These membranes can be used for several aqueous separations, including but not limited to water treatment, water softening, wastewater treatment, and separation and purification of organic molecules in aqueous solutions. Due to the chemical nature of these copolymers, the membranes exhibit improved resistance to chemical degradation by chlorine and strong resistance to fouling.
• copolymers comprising a plurality of zwitterionic monomeric units, a plurality of charged/ionizable monomeric units, and a plurality of hydrophobic monomeric units.
• thin film composite membranes comprising a porous support, and a thin film of the polymeric material, wherein the pore size of the porous support is larger than the effective pore size of the thin film of the polymer material.
• methods of size-based selection or exclusion comprising contacting a solution comprising a plurality of uncharged organic molecules of different sizes with a thin film composite membrane disclosed herein.
• methods of charge-based selection or exclusion comprising contacting a solution comprising a plurality of salts with a thin film composite membrane disclosed herein.
• Fig. l is a scheme that depicts polymer architecture/chemistry of a Charged Zwitterionic Amphiphilic Copolymer (CZAC), P(TFEMA-r-SBMA-r-MAA), and schematic description of its self-assembly when coated onto a support to form a membrane selective layer, featuring ⁇ l-2 nm hydrophilic domains that act as a network of effective nanochannels lined with carboxylate groups.
• CZAC Charged Zwitterionic Amphiphilic Copolymer
• P(TFEMA-r-SBMA-r-MAA) P(TFEMA-r-SBMA-r-MAA)
• Fig. 2 depicts the 1 H NMR spectrum of PTFEMA-SBMA-MAA-B1, indicating copolymerization.
• Fig. 3 depicts the 3 ⁇ 4 NMR spectrum of PTFEMA-SBMA-MAA-B2, indicating copolymerization.
• Fig. 4A depicts an SEM image of an uncoated Trisep UE50 support membrane.
• Fig. 4B depicts an SEM image of a PTFEMA-SBMA-MAA-B1 TFC membrane.
• Fig. 4C depicts an SEM image of a PTFEMA-SBMA-MAA-B2 TFC membrane.
• Fig. 5A is a bar graph depicts the rejection of neutral (Rib, RH, and VB12) and anionic (Na2S04, MO, AB45) solutes by PTFEMA-SBMA membrane, PTFEMA-SBMA- MAA-B1 membrane, and PTFEMA-SBMA-MAA-B2 membrane.
• Fig. 5B is a graph that depicts the rejection of sugars and dyes by membranes prepared as described in Example 2B.
• Fig. 6A is a bar graph that depicts the rejection of various salts at concentrations of 1 mM and 5 mM by PTFEMA-SBMA membrane, PTFEMA-SBMA-MAA-B1 membrane, and PTFEMA-SBMA-MAA-B2 membrane.
• Fig. 6C is a bar graph that depicts PTFEMA-SBMA-MAA-B2 rejection of various salts at concentrations of 1 mM and 5 mM.
• Fig. 7A is a bar graph that depicts the rejection of various neutral dyes.
• Fig. 7B is a bar graph that depicts the rejection of various anionic dyes and Na2SC>4
• Fig. 8A is a graph that depicts oil emulsion fouling resistance for PTFEMA-SBMA- MAA-B2 membrane (stabilized by Span80 neutral surfactant);
• Fig. 8B is a graph that depicts oil emulsion fouling resistance for PTFEMA-SBMA- MAA-B2 membrane (stabilized by DC 193 neutral surfactant).
• Fig. 9 is a graph that depicts the permeance of PTSBMA-SBMA-MAA before and after Clorox treatment.
• Fig. 10 is an IR spectrum that depicts the effect of chlorine treatment on PTFEMA- SBMA-MAA-B2 bond chemistry. FTIR spectra taken before and after 16 hours of immersion in 2,000 ppm sodium hypochlorite solution at pH 4.5.
• Fig. 11 is a graph that depicts the rearrangement of PTFEMA-SBMA-MAA-B1 upon exposure to a PBS solution, followed by the switchable flux behavior that was observed afterwards.
• Fig. 13 is a bar graph that depicts the rejections of Vitamin B 12 and Na2SC>4 before and after rearrangement via NaOH(aq) treatment.
• Fig. 14 is a bar graph that depicts the membrane permeance versus Filtration ID (in Table 5).
• Fig. 15 is a bar graph that depicts the permeance of rearranged PTFEMA-SBMA- MAA membranes in response to a basic solution containing calcium.
• Fig. 16 is graph that depicts the correlation between reaction mixture composition and the composition of the resultant terpolymer, indicating close to random monomer sequence.
• membranes that combine NF-type selectivity with fouling- and chlorine-resistance by leveraging the self-assembling properties of ZACs and modifying this polymer family to improve salt rejection. Specifically, disclosed are charged
• CZACs zwitterionic amphiphilic copolymers
• membranes prepared with CZAC selective layers through scalable manufacturing techniques are random or statistical terpolymers of three types of monomers: hydrophobic monomer, zwitterionic monomer, and acidic/ionizable monomer.
• the copolymers are linear, random, and statistical.
• the random/statistical architecture of the copolymers and zwitterion- zwitterion attractive forces grant this terpolymer the ability to self-assemble into a bicontinuous network comprised of 1-2 nm hydrophilic (zwitterionic/charged) and hydrophobic nanodomains.
• hydrophilic domains which act as an effective network of nanochannels with charged walls.
• the hydrophilic nanochannel is net charged due to the ionization of the incorporated functional groups (e.g. deprotonation of an acidic repeat unit, protonation of an amine group, dissociation of a sulfonate group), which enhances the rejection of charged solutes and salt ions. Due to the presence of zwitterionic groups, these membranes are highly fouling resistant.
• the use of a novel polymer chemistry enables high chlorine resistance, with no changes in performance upon exposure to 32,000 ppm. hours of chlorine.
• a zwitterionic repeat unit which leads to the formation of a bicontinuous network of hydrophilic/water permeable nano-domains that act as permeation pathways for water and aqueous solutions that contain solutes smaller than domain size, preferably typically ⁇ 5 nm, and preferably 0.6-3 nm, and more preferably 0.6-2 nm.
• a charged or ionizable repeat unit which imparts charge-based selectivity and ion retention properties through Donnan exclusion mechanisms.
• a relatively hydrophobic repeat unit which limits the swelling of the polymer in water and imparts the polymer stability in aqueous environments.
• This hydrophobic repeat unit is preferably derived from a monomer whose homopolymer is not soluble in water, and has a glass transition temperature above use temperature (e.g., above room temperature).
• the polymers which are termed“Charged Zwitterionic Amphiphilic Copolymers” (CZACs), may be synthesized from vinyl monomers (e.g., acrylates, methacrylates, acrylamides, styrene derivatives, acrylonitrile) using well-known polymerization methods (e.g., free radical polymerization).
• the polymers incorporate the three types of repeat units in roughly random/statistical order (as opposed to in large blocks of individual monomers), and have a molecular weight from 20,000 g/mol to 1,000,000 g/mol (preferably from 40,000 g/mol, or 100,000 g/mol to 1,000,000 g/mol).
• the copolymers are linear.
• the CZACs comprise -30-80 wt% of the hydrophobic monomer, 1-40 wt% of the charged monomer, and 1-40 wt% of the zwitterionic monomer. Broader ranges of compositions may be of use in other applications.
• SBMA Sulfobetaine methacrylate
• MPC methacryloxy phosphoryl choline
• CBMA carboxybetaine methacrylate
• Sulfobetaine-2-vinylpyridine Sulfobetaine methacrylate
• sulfobetaine-4-vinylpyridine sulfobetaine-vinyl imidazole
• several others comprising sulfobetaine, carboxybetaine, or phosphorylcholine moieties.
• Methacrylic acid (MAA)* Methacrylic acid
• acrylic acid acrylic acid
• styrene sulfonate acrylic acid
• TFEMA 2,2-trifluoroethyl methacrylate
• other fluorinated acrylates, methacrylates, and acrylamides e.g., pentafluoropropyl methacrylate, heptafluorobutyl methacrylate, pentafluorophenyl methacrylate
• styrene methyl methacrylate; acrylonitrile; other monomers that fit the above criteria.
• the CZACs may be coated onto porous supports by methods understood in the membrane industry (e.g., blade coating, non-solvent induced phase separation (NIPS), spray coating).
• TFC thin film composite
• a porous support with large pores, providing mechanical integrity e.g., blade coating, non-solvent induced phase separation (NIPS), spray coating.
• the CZAC layer typically contains a continuous dense layer of CZAC (i.e., not regular“through-pores” providing pathways for water permeation, with the exception of occasional defects that may appear in processing even if they are not desired); in other words, water should permeate through the CZAC, as the main transport mechanism, rather than through pores/holes in it.
• the resultant membranes exhibit size-based separation of neutral organic molecules, but also higher rejection of charged solutes than neutral solutes. This quality is useful for several applications where size-based separation is not sufficient. For example, if full or partial removal of contaminants is desired, the combination of size-based and charge-based rejection offered by these membranes can lead to better effluent quality.
• these membranes can separate two organic solutes (e.g., amino acids, drug compounds) from each other that differ by the presence of a charged group.
• the current membranes can be modified and tuned to increase salt rejection to address reverse osmosis (RO)/desalination processes and engineered osmosis (EO), or to access slightly larger pore sizes to have charge-selective tight ultrafiltration (UF) membranes.
• RO reverse osmosis
• EO engineered osmosis
• UF charge-selective tight ultrafiltration
• NF and RO/EO membranes almost universally have cross-linked polyamide selective layers. Such membranes suffer from two major problems: First, they are prone to fouling, requiring several pretreatment steps that impact the cost and energy efficiency of the overall process for desalination. Second, the membranes are highly sensitive to chlorine, which reacts with the selective layer. Chlorination is typically used to kill microorganisms in the incoming water to desalination facilities to prevent biofouling. Due to the chlorine sensitivity of commercial NF and RO membranes, the water is de- chlorinated before being fed to the NF or RO units, then chlorinated again before being sent to customers.
• the current membranes circumvent both of these issues: Zwitterionic groups are known and demonstrated to be highly resistant to fouling.
• the membranes are shown to be exceptionally resistant to fouling by an organic stream.
• the constituent polymers are not inherently prone to attack by chlorine.
• the membranes are shown to be stable to commercial chlorine bleach.
• the membranes may undergo a pore rearrangement when subjected to high-pH buffers.
• membranes with some CZAC selective layers When exposed to a high-pH buffer solution, membranes with some CZAC selective layers exhibit a one-time, irreversible and stable increase in permeability, along with a slight increase in pore size.
• CZACs from the hydrophobic monomer TFEMA, zwitterionic monomer SBMA, and ionizable monomer MAA can be synthesized by free radical polymerization at multiple monomer ratios.
• This copolymer self-assembles to create a network of hydrophilic nanodomains that act as water permeation pathways.
• the membranes can be coated onto commercial, large pore membranes as porous supports to create thin film composite (TFC) membranes.
• TFC thin film composite
• the membranes exhibit permeances (defined as flux/applied pressure difference) comparable to commercial RO and NF membranes. This can be further improved by decreasing coating thickness, and by changing polymer formulation.
• the membranes exhibit size-based selectivity between uncharged organic molecules, including Vitamin B12 and b-cyclodextrin, with rejections around 92%. Models of rejection lead to an estimated effective pore size around 2 nm. This pore size can be tuned through polymer chemistry and other methods to lower and higher values (1-5 nm appears to be an accessible range).
• the membranes exhibit significantly higher rejection of charged solutes than uncharged solutes of similar size.
• the membranes exhibit significant salt rejection, including NaSCri rejections around 95%, comparable with some NF membranes.
• the polymer is stable upon exposure to chlorine bleach (e.g., at pH 4).
• the membranes are highly resistant to fouling by an oil emulsion.
• the membranes Upon exposure to buffers with relatively high pH, the membranes exhibit a one-time increase in flux, accompanied with a slight decline in rejection. The new flux and pore size is stable; the change is not reversible. Additionally, the membranes attain switchable flux in different ionic solutions, which may be controlled by the cation present in the solution.
• copolymers comprising a plurality of zwitterionic monomeric units, a plurality of charged/ionizable monomeric units, and a plurality of hydrophobic monomeric units.
• the molecular weight of the copolymer is 20,000 g/mol to 1,000,000 g/mol. In some embodiments, the molecular weight of the copolymer is 40,000 g/mol to 1,000,000 g/mol. In some embodiments, the molecular weight of the copolymer is 100,000 g/mol to 1,000,000 g/mol.
• the zwitterionic monomeric units constitute 1-40 wt% of the copolymer. In some embodiments, the charged/ionizable monomeric units constitute 1-40 wt% of the copolymer. In some embodiments, the hydrophobic monomeric units constitute 30-80 wt% of the copolymer.
• each of the zwitterionic monomeric units is formed from a monomer comprising sulfobetaine, carboxybetaine, or phosphorylcholine moieties.
• each of the zwitterionic monomeric units is formed from a monomer selected from the group consisting of sulfobetaine methacrylate (SBMA), methacryloxy phosphoryl choline (MPC), carboxybetaine methacrylate (CBMA), sulfobetaine-2-vinylpyridine, sulfobetaine-4-vinylpyridine, and sulfobetaine-vinyl imidazole.
• each of the zwitterionic monomeric units is formed from sulfobetaine methacrylate (SBMA).
• each of the charged/ionizable monomeric units is formed from a monomer selected from the group consisting of a methacrylate, an acrylate, an acrylamide or a styrene derivative comprising carboxylic acid, sulfonate, phosphate, or amine moieties.
• each of the charged/ionizable monomeric units is formed from a monomer selected from the group consisting of methacrylic acid (MAA), acrylic acid, 2-carboxy ethyl acrylate, 2-carboxy ethyl methacrylate, styrene sulfonate, 3- sulfopropyl acrylate, 3-sulfopropyl methacrylate, 2-acrylamido-2-methyl-l-propanesulfonic acid, 2-(dimethylamino)ethyl methacrylate, 2-(diethylamino)ethyl methacrylate, 2- aminoethyl methacrylate, [2-(methacryloyloxy)ethyl]trimethylammonium chloride, [2- (acryloyloxy)ethyl]trimethylammonium chloride, 2-(diethylamino)ethyl acrylate, 2- (dimethylamino)ethyl acrylate,
• each of the charged/ionizable monomeric units is formed from methacrylic acid (MAA).
• each of the hydrophobic monomeric units is formed from a monomer selected from the group consisting of styrene, methyl methacrylate, acrylonitrile, a fluoroalkyl acrylate, a fluoroaryl acrylate, a fluoroalkyl methacrylate, a fluoroaryl methacrylate, a fluoroalkyl acrylamide, and a fluoroaryl acrylamide.
• each of the hydrophobic monomeric units is formed from a monomer selected from the group consisting of a fluoroalkyl acrylate, a fluoroaryl acrylate, a fluoroalkyl methacrylate, a fluoroaryl methacrylate, a fluoroalkyl acrylamide, and a fluoroaryl acrylamide.
• each of the hydrophobic monomeric units is formed from a monomer selected from the group consisting of 2,2-trifluoroethyl methacrylate (TFEMA), pentafluoropropyl methacrylate, heptafluorobutyl methacrylate, and pentafluorophenyl methacrylate.
• each of the hydrophobic monomeric units is formed from 2,2-trifluoroethyl methacrylate (TFEMA).
• hydrophobic monomeric units are characterized in that a homopolymer formed thereof has a glass transition temperature above room temperature.
• the copolymer is a random copolymer.
• the copolymer is a statistical copolymer.
• the copolymer is a linear copolymer. In some embodiments, the copolymer is poly((sulfobetaine methacrylate)-ra «ifow- (methacrylic acid)-ra fow-(2,2-trifluoroethyl methacrylate)).
• polymeric materials comprising a plurality of the copolymers.
• the polymeric material is in the form of a thin film.
• thin film composite membranes comprising a porous support, and a thin film of the polymeric material, wherein the pore size of the porous support is larger than the pore size of the thin film of the polymer material.
• the thin film of the polymeric material has a thickness of 1 nm to 10 pm. In some embodiments, the thin film of the polymeric material has a thickness of 1 nm to 3 pm. In some embodiments, the thin film of the polymeric material has a thickness of 1 nm to 1 pm.
• the thin film of the polymeric material has an effective pore size of 0.1 - 5 nm. In some embodiments, the thin film of the polymeric material has an effective pore size of 0.6 - 3 nm. In some embodiments, the thin film of the polymeric material has an effective pore size of 0.6 - 2 nm.
• the thin film composite membrane exhibits resistance to fouling by an oil emulsion.
• the thin film composite membrane is stable upon exposure to chlorine bleach (e.g., at pH 4).
• the thin film composite membrane undergoes a one-time, irreversible change in pore size upon exposure to buffers with high pH.
• the thin film composite membrane exhibits size-based selectivity between uncharged organic molecules.
• the thin film composite membrane rejects charged solutes and salts.
• methods of size-based selection or exclusion comprising contacting a solution comprising a plurality of uncharged organic molecules of different sizes with a thin film composite membrane disclosed herein.
• TFEMA trifluoroethylmethacrylate
• SBMA sulfobetaine methacrylate
• MAA methacrylic acid
• the mixture was then allowed to stir at room temperature for two days to dissolve the zwitterionic monomer. Afterwards, the flask was sealed with a rubber septum, purged with N2 for 40 minutes, and then plunged into a 70 °C oil bath with stirring. After 20 hours, the reaction was terminated by exposure to air and the addition of MEHQ (0.5 g). For precipitation, the viscous polymer solution was then poured into an 800 mL mixture of ethanol and hexane (1 : 1 volume ratio.) The polymer was then cut into small pieces, and washed via stirring in an 800 mL mixture of ethanol and hexane (1 : 1 volume ratio) for over 12 hrs. This wash cycle was repeated 2 times.
• the composition of the purified polymer was calculated from the 1 H-NMR spectrum (Fig. 2), through integration of the following three sets of peaks: (1) c”, (2) e’, (3) c, c’. The composition was calculated as 61.9 wt% TFEMA, 31.7 wt% SBMA, and 6.4 wt% MAA.
• a random/statistical terpolymer of TFEMA, SBMA, and MAA was synthesized as follows. First, SBMA (2.80 g) and DMSO (87 mL) were added to a 250 mL flat bottom reaction flask. Temperature was raised to 70°C to dissolve the zwitterionic monomer, and then returned to room temperature. During this the cool-down period, both TFEMA and MAA were purified using basic alumina columns (VWR). Following this, purified TFEMA (4.49 mL), purified MAA (1.86 mL), LiCl (0.10 g), and AIBN (9.8 mg) were added to the reaction flask.
• the flask was sealed with a rubber septum, purged with N2 for 30 minutes, and then plunged into a 70°C oil bath with stirring. After 20 hours, the reaction was terminated by exposure to air and the addition of MEHQ (0.7 g) dissolved in approximately 5 mL of DMSO. For precipitation, the viscous polymer solution was then poured into a 900 mL mixture of ethanol and hexane (1 : 1 volume ratio). The polymer was then cut into small pieces, and washed via stirring in a 900 mL mixture of ethanol and hexane (1 : 1 volume ratio) for 12 hrs. This wash cycle was repeated 3 times.
• the composition of the purified polymer was calculated from the 1 H-NMR spectrum (Fig. 3), through integration of the following three sets of peaks: (1) c”, (2) e’, (3) c, c ⁇ The composition was calculated as 52.2 wt% TFEMA, 34.9 wt% SBMA, and 12.9 wt% MAA.
• the terpolymer has a near-random monomer sequence.
• the terpolymer composition was similar to the initial reaction conditions, and the yields were -70%. This is in contrast with the block architecture that is generally associated with self-assembling copolymers.
• the term“random” is not strictly applied. To best communicate the polymer architecture to a wide audience, the terpolymers will therefore be referred as being random.
• TFC thin film composite
• Example 3 A Formation of TFC membranes from PTFEMA-SBMA-MAA-B 1
• a TFC membrane was prepared using the polymer described in Example 1A.
• the copolymer was first dissolved in trifluoroethanol (TFE) at 0.11 g copolymer/ mL TFE.
• TFE trifluoroethanol
• the solution was then filtered using a 1 pm glass syringe filter, degassed via heating to 50°C for 1 hour, and allowed to cool back down to room
• a membrane was prepared using the polymer described in Example IB.
• the copolymer was first dissolved in trifluoroethanol (TFE) at 0.11 g copolymer/ mL TFE.
• TFE trifluoroethanol
• the solution was then filtered using a 1.2 pm glass syringe filter, degassed via heating to 50°C for 1 hour, and allowed to cool back down to room temperature.
• a Gardco universal blade applicator with a 20 pm gate setting was used to coat the copolymer solution onto a PES ultrafiltration support membrane (Trisep UE50). After coating, the film of polymer solution was allowed 15 seconds to evaporate.
• TFC thin film composite
• SEM Scanning electron microscopy
• the pure water permeance of the membranes described in Examples 2A and 2B was measured, and compared to membrane prepared from PTFEMA-SBMA.
• 10 mL Amicon 8010 stirred cells in dead-end mode was used.
• the membrane swatch area was 4.1 cm 2
• the stirring speed was 500 RPM
• the pressure was 30 psi for PTFEMA-SBMA-MAA-B 1 membranes and 50 psi for PTFEMA-SBMA- MAA-B2 membranes.
• Ohaus Scout Pro scales that were connected to a computer was used. Synchronized measurements of permeate mass versus time allowed for the measurement of membrane flowrate, which allowed for the calculation of membrane permeance.
• Fig. 5B shows the rejection of neutral sugars and neutral dye molecules. Size selectivity is observed for the neutral solutes that were tested, with Vitamin B12 (1.48 nm hydrated diameter) and b-cyclodextrin (1.54 nm hydrated diameter) rejection around 92% (Table 2). The effective pore size was calculated to be 1.95 nm by fitting the rejection data for sugar molecules to the Extended Nernst Planck Equation with steric hindrance boundary conditions.
• Fig. 6A shows that PTFEMA-SBMA-MAA-B1 membrane and PTFEMA-SBMA- MAA-B2 membrane had a greater rejection of charged solutes than PTFEMA-SBMA membrane. Since neutral solute rejection was equivalent for all three membranes, this finding is evidence that MAA grants anion selectivity to CZAC membranes.
• the highest rejection was that of Na2SC>4, in the range of 93-95%.
• the rejection of CaSCri was in the range of 40- 70%, and the rejection of NaCl was in the range of 30-60%.
• the effective pKa ⁇ 4.0 is well below the pKa of 4.78 that is reported for MAA monomer. This implies that MAA is approximately 10 times more reactive when incorporated into the CZAC nanostructure than when in free solution. This contradicted expectations, since it is generally found that confinement leads to reduced MAA reactivity.
• Fig. 6C shows the rejection of charged solutes.
• Fig. 6C demonstrates the following two notable performance features of PTFEMA-SBMA-MAA-B2 membranes: (1) 96% rejection of both 1 mM (142 ppm) Na2SC>4 and 1 mM (110 ppm) LriSCri solutions; (2) 93% rejection of both 5 mM (710 ppm) Na2SC>4 and 5 mM (550 ppm) L12SO4 solutions (Table 3).
• the rejection of CaSCri and MgSCri was in the range of 40-70%, and the rejection of NaCl and LiCl was in the range of 30-60%. Rejection of solutes decreased with increasing feed concentration, which is consistent with Donnan exclusion.
• Fig. 7A and Fig. 7B show the rejection of the various dyes and Na2SC>4.
• Table 4 tabulates the abbreviations, calculated diameter, charge, and rejection of the solutes by the PTFEMA-SBMA-MAA-B1 membranes and the PTFEMA-SBMA membranes.
• the rejection of neutral dyes is similar for PTFEMA-SBMA-MAA-B 1 membranes and
• PTFEMA-SBMA membranes which indicates a similar effective pore size.
• rejection of anionic solutes by the PTFEMA-SBMA-MAA-B 1 membranes is greater than that of the PTFEMA-SBMA membranes.
• MAA being a weak acid, attains a negative charge upon deprotonation in aqueous solution.
• MAA is incorporated in the zwitterionic domain of the self-assembled PTFEMA-SBMA-MAA-B 1 selective layer, then it could endow the nanochannels of the membrane with a negative charge. This would lead to an enhanced rejection of ionic species though a well-documented phenomenon known as Donnan exclusion.
• Zwitterions are one of the most fouling resistant materials currently known. This is because the foulant-surface adsorption event that constitutes fouling is limited by the strong hydration shell that surrounds zwitterions (AGindration— 500 kJ/mol according to simulations).
• AGindration— 500 kJ/mol according to simulations ABI- 500 kJ/mol according to simulations.
• membranes comprised of random zwitterionic copolymers are highly fouling resistant, which proves that zwitterions are still able to act as anti-fouling agents from within the confines of the membrane nanostructure.
• dead-end filtration using different model foulants is performed.
• Commercial NF membranes were used as benchmarks. The membranes were fouled for 24 hours, and the initial flux of the CZAC membrane was matched to that of the benchmark.
• the fouling resistance of the PTFEMA-SBMA-MAA-B2 membrane described in Example 3B was measured using oil-in-water emulsions. The purpose of this was to show that the membranes are fouling resistant, which is a vital feature for any membrane that is pitted against a fouling-prone feedstock.
• Fig. 8A and Fig. 8B show the above two fouling experiments performed. All reveal PTFEMA-SBMA-MAA-B2 membranes to be fouling resistant.
• Fig. 8C shows the fouling resistance of PTFEMA-SBMA-MAA-B1 against BSA/ CaCh (1000 ppm and 10 mM, respectively), with the NP30 (Microdyne; PES) serving as the control.
• BSA is a common model protein foulant, and calcium salts were added to increase its adsorption propensity.
• PTFEMA-SBMA-MAA-B1 was seen to foul significantly less than the NP30 throughout the 24 hours fouling experiment. After a brief rinse of the membranes, PTFEMA-SBMA-MAA-B1 had a complete recovery of flux, which verifies that the adsorption event was reversible. The NP30, in contrast, was irreversibly fouled.
• Fig. 8D shows the fouling resistance of PTFEMA-SBMA-MAA-B2 against humic acid / alginate (1000 ppm each), with the UA60 (Trisep; PA) serving as the control.
• the pH was reduced with HC1 to 4.5 in order to increase adsorption propensity.
• PTFEMA-SBMA- MAA-B2 fouled less than the UA60 throughout the 24 hours fouling experiment.
• PTFEMA-SBMA-MAA-B1 had a 93% recovery of initial flux, with the permeance climbing back to 96% of the initial value after 5 hours.
• the UA60 suffered a greater initial drop (82% recovery immediately after rinse), and eventually reached 93% recovery after 13 hours.
• PTFEMA-SBMA-MAA-B1 membrane was exposed to a solution of containing a chlorinated solution, prepared by diluting commercial Clorox bleach and adjusting its pH to an acidic value in agreement with commercial cleaning procedures.
• the purpose of this was to demonstrate that the PTFEMA-SBMA-MAA-B1 membranes are resistant to chlorine, which would enable the membranes to be cleaned with sodium hypochlorite, a commonplace disinfectant.
• the polyamide membranes that represent the cornerstone of the NF market are not stable upon exposure to chlorine, which is a major disadvantage of the technology.
• Fig. 9 reveals that the permeance of the membrane remained unaltered upon treatment with the chlorinated solution, indicating that the membrane remains stable upon exposure to chlorine.
• Fig. 10 shows the effect of chlorine treatment on PTFEMA-SBMA- MAA-B2 bond chemistry.
• FTIR spectra taken before and after 16 hours of immersion in 2,000 ppm sodium hypochlorite solution at pH 4.5 shows that the structure remained in intact before and after the exposure.
• PBS alkaline buffer system
• the permeance increased from the initial value of -1.8 LMH/bar to - 2.8 LMH/bar upon initial exposure to the 10 mM solution of PBS.
• DIW distilled water
• the permeance increased to - 5.1 LMH/bar in distilled water (DIW.)
• DIW distilled water
• FIG. 12B show the results of this experiment, and reveals that NaOH (aq) is indeed able to bring about the base rearrangement observed with PBS. It is also noted that no rearrangement was observed with PTFEMA- SBMA membranes.
• Fig. 13 demonstrates that the rejection of Vitamin B12 and Na 2 S0 4 both decreased after exposure to NaOH (aq) , although it is noted that Vitamin B12 rejection declined more than Na 2 S0 4.
• Example 2B was consistently measured using a simple mass balance. The results for filtration experiments, which captured 17 different uncharged/charged/dye solutes, is shown in Fig. 14 (see Table 6 for the tabulation of filtration ID.) Membrane flux was unaffected during and after filtration with these solutes. This further implicates interactions with bases as the root cause of the rearrangement for PTFEMA-SBMA-MAA membranes.

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