TWI423843B - Low biofouling filtration membranes and their forming method - Google Patents

Description

Low biological fouling filter membrane and method of forming same

The present invention relates to a low biofouling filter membrane, and more particularly to a fluorine-containing filter membrane grafted with a homopolymer or copolymer containing a zwitterionic group to achieve resistance. The purpose of biological scaling.

The biomolecular structure of a protein is quite complex, and it has both a hydrophilic region and a hydrophobic region. Biomolecules are highly deformable and are easily adsorbed on surfaces with hydrophobic groups. Therefore, many materials with hydrophilic surfaces are widely used to reduce protein adsorption. However, the above materials are often unable to effectively prevent the adsorption of cells, bacteria or other microorganisms. Even a small amount of protein adsorption can lead to severe biofouling of the membrane surface during subsequent material use. For example, for plasma fibrinogen (FIB), the surface of the material must maintain an adsorption capacity of less than 5-10 ng/cm2 to avoid subsequent adsorption of platelets, thereby increasing the blood compatibility of the material. The limitations of such ultra-low adsorption quantities are very common in related applications.

However, only a very small number of materials can meet "nonfouling materials" or "ultra low fouling materials (superlow) Fouling materials)" restrictions. Modification of the surface of the material by polyethylene (poly (ethylene glycol); PEG) or oligo (ethylene glycol) (OEG) is an in-depth study to avoid protein adsorption. One of the possible reasons why PEG can avoid protein adsorption is the electrostatic repulsion effect. However, PEG or OEG is easily decomposed in the presence of oxygen or transition metal ions (often present in biochemical related solutions).

Polymers with phospholipocholine (PC) groups or material surfaces have been shown to be effective in reducing protein adsorption, since phospholipid thiol base (PC) groups are present in the outer layers of the cell membrane, so they are It is considered a biomimetic anti-biofouling material. In addition, hydration with PC materials is also considered to be one of the possible reasons why PCs can avoid protein adsorption. However, due to the hydration of PC materials, its long-term operational stability is not good. For example, 2-methacryloyloxyethyl phosphorylcholine (MPC) is very sensitive to moisture and is not easy. Synthesis and use. In view of this, it is still necessary to develop new low biofouling filter materials.

In view of the above background, the present invention provides a new low fouling filtration membrane to overcome various disadvantages of the prior art.

One of the objects of the present invention is to use a sulfobetaine sulfobetaine Polymers) Surface modification of porous fluorine-containing substrates. Similar to a polymer having a phospholipcholine (PC) group, polysulfonate sulfonate belongs to polybetaine polymers, and its structural feature is that the cationic group and the anionic group are present in the same side group. On the group. Compared with MPC, sulfobetaine methacrylate (SBMA) is easier to synthesize and use.

Another object of the present invention is to control the grafting reaction of a highly polar sulfonate urethane monomer on the surface of a chemically inert, hydrophobic fluoropolymer. The invention sequentially activates the surface of the substrate by plasma, performs surface initiation graft polymerization using a functional monomer having a halogen group, and finally, by atom transfer radical polymerization (ATP) Grafting to form sulfobetaine polymers on the halogen groups on the surface of the substrate.

A further object of the present invention is to use a fluorine-containing filter membrane grafted with a zwitterionic group for protein separation experiments. The results of the filtration experiments showed that the irreversible membrane fouling of bovine serum albumin (BSA) and two plasma proteins: serum albumin (albumin) and globulin (globulin) was significantly reduced. The results of the circulating filtration experiments on bovine serum albumin showed that the extremely low irreversible membrane fouling ratio (Rir) was in the first cycle (13%) and the zero fouling rate was in the second cycle. A more rigorous experiment is to filter gamma-globulin (gamma) -globulin), when using pure PVDF for cyclic filtration experiments, the pure PVDF to the third cycle has been severely fouled; however, it is modified with the polysulfonated polyamine-polymethyl acrylate (polySBMA) provided by the present invention. The membrane, irreversible membrane fouling rate (Rir) was only 4.7% in the third cycle. Accordingly, the present invention can meet economic benefits and industrial applicability.

According to the above objects, the present invention discloses a method for forming a low biofouling filter membrane. First, ozone treatment is performed on a porous fluorine-containing substrate to form a peroxide group on the surface of the fluorine-containing substrate. . Then, a first graft polymerization reaction is initiated by a peroxide group, and the first graft polymerization reaction is carried out under a chemical composition comprising at least one functional monomer. Thereby a halogen functional group is introduced to the surface of the substrate. Finally, a second graft polymerization reaction is carried out to introduce a zwitterionic group to the surface of the substrate, thereby forming the above-described low biofouling polymer composite film.

The invention discussed herein is a low biofouling filter membrane and method of forming the same. In order to thoroughly understand the present invention, detailed steps and compositions thereof will be set forth in the following description. Obviously, the practice of the invention is not limited to the specific details that are apparent to those skilled in the art. On the other hand, well-known components or steps are not described in detail to avoid making the invention unnecessary. The limit. The preferred embodiments of the present invention are described in detail below, but the present invention may be widely practiced in other embodiments, and the scope of the present invention is not limited by the scope of the following patents. .

Poly(vinylidene fluroride); PVDF is widely used in the manufacture of microfiltration membranes and ultrafiltration membranes because of its excellent chemical stability, good mechanical strength and high thermal stability. (ultratiltration membrane) with nanofiltration membrane. The most important property of polytetrafluoroethylene (PVDF) in biomedical applications is to reduce the non-specific absorption of biomolecules, especially when the hydrophobic PVDF surface contacts the living system. In general, the surface of a membrane made of a hydrophobic material often causes biofouling to occur, and the amount of filtrate is significantly reduced over time, particularly for proteins, platelets or filtration systems containing cell solutions. Theoretically increasing the hydrophilic groups on the surface of the membrane can effectively reduce fouling, since most of the fouling occurs from the interaction between biomolecules (eg, proteins) and the surface of the hydrophobic membrane. Therefore, an ideal anti-fouling film should have excellent overall mechanical strength, usually using a hydrophobic film (for example: PVDF), but the surface should have anti-fouling properties, usually imparting hydrophilicity to the surface of the film.

The first embodiment of the present invention discloses a low biofouling polymer composite membrane which can be applied to the following ranges: separation of proteins from peptides, purification of human blood to remove viruses or leukocytes, Remove microbial from wastewater and dry fine Preservation, purification, and concentration of cells. The low biofouling polymer composite film disclosed in the embodiment comprises a fluorine-containing substrate (fluorine-based membrane) activated by treatment (particularly ozone treatment) and a branched polymerization having a zwitterionic group. A branched polymer layer formed on the fluorine-containing substrate by surface grafting.

In a preferred embodiment of the present embodiment, the surface grafting reaction is a two-step polymerization. More than or equal to 5 mol% of a halogen-containing monomer such as 2-(2-bromoisobutyryloxy)ethyl acrylate or 2-(2-choloisobutyryloxy)ethyl acrylate is used in the first step. Next, the second step is atom transfer radical polymerization (ATRP), and the atom transfer radical polymerization reaction is initiated by the halogen-containing monomer; A monomer having a zwitterionic group is used to form a graft polymer, wherein the zwitterionic group accounts for 10% or more by weight of the graft polymer. In order to effectively reduce the amount of scale adsorption on the surface of the filter membrane, the graft density and chain length of the graft polymer described above need to be greater than or equal to 0.3 chains/nm 2 and 50 units, preferably greater than or equal to 0.5 chains/nm 2 and 100 units. .

Furthermore, the above zwitterionic groups comprise one of the following groups: Phosphobetaine, sufobetaine, carboxylbetaine and its "derivatives". By "derivative" herein is meant a mixture of phosphobetaine, sufobetaine or carboxylbetaine with a compound containing an equivalent molar charged group. Several examples are shown. Commonly charged compounds are Aminoethyl methacrylate hydrochlorides, 2-(Dimethylamino)ethyl methacrylate or 2-(Methacryloyloxy)ethyl trimethylammonium chloride; common negatively charged compounds are 2-Carboxyethyl acrylate or 3-Sulfopropyl methacrylate. .

A second embodiment of the present invention discloses a method for forming a low biofouling polymer composite film, which first provides a fluorine-containing substrate. Next, the fluorine-containing substrate is subjected to an ozone treatment to form a first substrate, wherein the surface of the fluorine-containing substrate reacts with ozone to form a peroxide, wherein the peroxide group comprises an alkyl- Peroxide and hydroxyl-peroxide. Then, a first graft polymerization reaction is performed on the first substrate, which is initiated by a peroxide group of the first substrate, and the first graft polymerization reaction system comprises at least one function. The chemical composition of the monomer is carried out, wherein the functional monomer comprises at least one acrylate group and at least one halogen functional group, preferably chlorine (Cl) or bromine (Br), functional monomer The second substrate having a halogen functional group is formed by reacting an acrylate group with a peroxide group of the first substrate, and the functional single system is polymerized with each other by an acrylate group. In addition, a preferred option for the above functional monomer is 2-(2-bromoisobutyryloxy)ethyl acrylate (BIEA). The first graft polymerization temperature described above needs to be higher than the peroxide decomposition temperature (about 70 ° C).

After the first graft polymerization reaction is completed, a second graft polymerization reaction is performed on the second substrate, and the second graft polymerization reaction is initiated by a halogen functional group of the second substrate, and the second graft polymerization is performed. The reaction is carried out in a chemical composition comprising a macro-monomer, wherein the macromonomer comprises at least one acrylate group and at least one zwitterionic group, and the macromonomer system is based on an acrylate group. Reacting with a halogen functional group of the second substrate, and the macromono system is polymerized with each other by an acrylate group, thereby forming a low-scoring fluorine-containing filter membrane having a zwitterionic group, the zwitterionic group It is used to reduce the amount of scale adsorption on the surface of the filter membrane. The above macro-monomer is a sulfobetaine acrylate, preferably sulfobetaine methacrylate (SBMA). Further, the graft density and chain length of the graft polymer described above need to be greater than or equal to 0.3 chains/nm 2 and 50 units, preferably greater than or equal to 0.5 chains/nm 2 and 100 units.

In the present embodiment, the fluorine-containing substrate may be a porous fluorine-containing substrate and include one of the following groups: a micro-filtration membrane, an ultra-filtration membrane, and a nai. Nano-filtration membrane. In addition, the above-mentioned fluorine-containing substrate material The material comprises one of the following groups: polyvinylidene fluoride (PVDF), copolymers of tetrafluoroethylene and perfluoro(propyl vinyl ether), copolymers of tetrafluoroethylene and perfluoro-2,3-dimethyl-1,3-dioxole, copolymers of tetrafluoroethylene and vinyl fluoride ,poly(vinyl fluoride),poly(vinylidene fluoride),polychlorotrifluorethylene,vinyl fluoride/vinylidene fluoride copolymers, and vinylidene fluoride/hexafluoroethylene copolymers.

In the present embodiment, the ozone treatment described above uses an ozone/oxygen mixed fluid in which the ozone concentration ranges from about 5 g/m3 to 50 g/m3, and the treatment time ranges from about 5 minutes to 60 minutes. Further, the first graft polymerization reaction and the second graft polymerization reaction described above may be carried out under atmospheric pressure without additionally adding an initiator. On the other hand, depending on the type of reaction, the first graft polymerization reaction and the second graft polymerization reaction are controlled/living free radical polymerization, preferably atom transfer radicals. Atom Transfer Radical Polymerization (ATRP).

Example 1

PVDF ultrafiltration membrane grafted with zwitterionic groups in bovine serum albumin (BSA) and two plasma proteins: Separation experiment of serum albumin (albumin) and globulin (globulin)

1. Materials and methods

A. Materials

Sulfuric acid polyethylammonium methacrylate [2-(Methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)-ammonium hydroxide (sulfobetaine methacrylate, SBMA) macromonomer was purchased from Monomer-Polymer & Dajac Laboratories, Inc. [Copper (I) bromide] (99.999%), 2-bromoisobutyryl bromide (BIBB, 98%), pyridine [98%], hydroxyethyl acrylate [2-Hydroxyethyl] Acrylate] (97%), 2,2'-bipyridine [2,2'-bipyridine] (BPY, 99%) and triethylamine (99%) purchased from Sigma-Aldrich, isopropanol [Isopropyl] Alcohol] (IPA, 99%) was purchased from Sigma-Aldrich and used as a solvent for ozone treatment and graft copolymerization. N,N-Dimethylethylamine N,N-Dimethylacetamide (DMAc, 98%) was purchased from Sigma-Aldrich as a casting solution, and 2-(2-bromoisobutyryl)ethyl acrylate (BIEA) was synthesized by itself. The previously published method was carried out by reacting 2-bromoisobutylphosphonium bromide (BIBB) with 2-Hydroxyethyl acrylate, and Phosphate buffer saline (PBS) was purchased from Sigma.

B. Surface copolymerization

The PVDF ultrafiltration membrane used in the experiment was prepared by wet phase inversion. The casting solution contained DMAc, 15wt% PVDF and pore-forming agent poly(ethylene glycol) (PEG8000, PVDF/PEG). The weight ratio was 4:1), and the casting solution was stirred at 60 ° C for 24 hours, and then allowed to stand for 6 hours to defoam the solution. The defoamed casting solution is scraped into a casting solution having a thickness of 300 μm on a glass substrate by a doctor blade, and then the glass substrate is rapidly immersed in a coagulation bath having a secondary distilled water at 25 ° C together with the casting liquid above. After phase separation, an ultrafiltration membrane was formed, and the resulting ultrafiltration membrane was placed in a vacuum oven overnight to completely remove residual solvent.

Referring to the first figure, a PVDF ultrafiltration membrane having an area of about 40 cm2 is first treated with an ozone/oxygen mixture, wherein the ozone/oxygen mixture is bubbled into 80 ml of isopropanol at a flow rate of 6 L/min, time. For 30 minutes, the ozone concentration was 46 g/L (25 ° C), and the ozone production machine model was Model OG-10PWA, Ray-E Creative Co., Ltd Taiwan. After completion of the ozone treatment procedure, the PVDF ultrafiltration membrane treated in the reaction flask was rapidly cooled in an ice bath at 4 ° C, and the reaction flask was filled with argon for 10 minutes, and then placed in an IPA solution to prepare.

The ozone-treated PVDF ultrafiltration membrane and 30 mL of IPA containing 10 wt% of BIEA monomer were placed in a reaction flask, and then the reaction flask was argon gas. (argon) was filled for 5 minutes, then placed in an oil bath at 80 ° C and heated continuously. After reacting for 24 hours, a PVDF ultrafiltration membrane (hereinafter abbreviated as PVDF-g-PBIEA) grafted with PBIEA was formed and stored in IPA. The unreacted monomer and homopolymer contained in PVDF-g-PBIEA were extracted in a sonication bath with a washing solution (double distilled water and acetone), and then placed in a vacuum oven to dry.

A surface co-polymerization of PVDF-g-PBIEA using a sulfonic acid polylacon-methyl acrylate (SBMA) macromonomer, which is a surface-initiated atom transfer radical polymerization (ATRP) The schematic diagram of the reaction mechanism is shown in the first figure. PVDF-g-PBIEA having an area of about 40 cm 2 was placed in a 30 mL methanol solution (SBMA content ranging from 0.56 to 5.5 g) containing SBMA macromonomer to achieve the desired graft density of polySBMA. The above PVDF-g-PBIEA and methanol solution were placed in a single-necked round bottom bottle and degassed using pure argon for 20 minutes. 316 mg of 2,2'-bipyridine and 100 mg of CuBr were sequentially added to the above solution, and degassed with pure argon for 5 minutes, then placed in an oil bath at 40 ° C and continuously stirred. After reacting for 24 hours, a PVDF-g-PBIEA composite membrane grafted with polySBMA (hereinafter abbreviated as PVDF-g-polySBMA) was formed, and PVDF-g-polySBMA was stored in methanol followed by a washing solution (secondary distilled water and methanol). ) Extracted. The formed PVDF-g-polySBMA was placed in a vacuum oven to completely remove residual solution Agent. In addition, all of the above surface modification procedures have the same conditions.

C. Surface characterization

The chemical composition of the PVDF film modified with PBIEA and polySBMA surface is measured by a FT-IR spectrophotometer (Perkin-Elmer Spectrum One) and zinc selenide (ZnSe) as an internal reflection element. The map obtained in the second time was an average of 32 scans with a resolution of 4 cm ^-1 . The composition of the surface of the film was analyzed by X-ray photoelectron spectroscopy (XPS) using a PHI Quantera SXM/Auger spectrometer with a monochromated Al KR X-ray source (1486.6 eV photons). The energy of the emitted electrons is measured by a hemispherical energy analyzer, and the passing energy range is controlled at 50 to 150 eV. All data collection systems are located in the same area, which is located at a 45 degree exit angle from the surface of the sample. Refer to the binding energy (BE) size to set the maximum peak in the C 1s map to 284.6 eV, and use the Shirley background subtraction method and a series of Gaussian peaks to obtain higher values in the C 1s map. The resolution, in which the data analysis software was purchased from Service Physics, Inc. The graft density of polySBMA on the PVDF membrane is determined by the weight gain compared to pure PVDF, while also taking into account the outer surface area of the membrane. Before the weight measurement, the film was placed in a vacuum oven overnight (50 ° C), and each time the surface was modified and the weight was measured, three separate test pieces were used for measurement. average value. The contact angle of water was measured at 25 ° C using a contact angle meter (Automatic Contact Angle Meter, Model CA-VP, Kyowa Interface Science Co., Ltd Japan), and the distilled water droplets were placed in ten different sample areas during the measurement. The average value of the three independent test pieces is measured to calculate the contact angle. The surface morphology (7 keV) of the surface treated PVDF ultrafiltration membrane was observed using a scanning electron microscope (JEOL JSM-5410).

D. Membrane protein adsorption

Bovine serum albumin (BSA) and γ-globulin (99%, purchased from Sigma-Aldrich) were used in the adsorption experiment of PVDF ultrafiltration membrane (PVDF-g-polySBMA). The Bradford method was performed according to the standard Bio-rad protein assay procedure. A PVDF ultrafiltration membrane having an area of about 20 cm ² was first washed in 20 mL of ethanol for 30 minutes and placed in a clean test tube. Then, it was soaked in 20 mL of PBS solution for 30 minutes. The membrane was separately inoculated into 5 mL of 0.1 M PBS solution containing 1 mg/mL BSA or 1 mg/mL γ-globulin (pH 7.4), and allowed to stand at 37 ° C for 24 hours. The film was contacted with a dye (containing Coomassie Brilliant Blue G-250) for 5 minutes. The absorption of the test piece at 595 nm was measured by an ultraviolet/visible spectrometer.

E. Ultrafiltration experiment results

A one-way cell filtration system is connected to a nitrogen and solution reservoir to test the filtration performance of the prepared membrane. The above filtration units were purchased from HP 4750 stirred cells, Sterlitech Corp., having a capacity of 300 mL and an inner diameter of 49 mm. Before the membrane was subjected to the filtration test, it was washed with double distilled water for 30 minutes at 1.5 atm, and the ultrafiltration experiments were carried out under the conditions of 25 ° C, 1 atm and 300 rpm. The amount of filtrate ( J _wi or J _Pi ) of the i-th cycle is continuously measured until it is stable, and its calculation formula is as follows: The parameters Vwi, VPi, A and Δt represent the filtrate amount (unit L), the membrane area (unit m2) and the filtration time (unit hours) of the pure water and protein solution in the i-th cycle, respectively. In each filtration cycle experiment, the filtration unit was emptied and injected with a concentration of 1 mg/mL protein solution, and then the amount of filtrate was continuously measured until the flow rate was stable. The protein rejection ratio (R) was determined by the following formula. Calculation: The parameters C _p and C _f are the protein concentrations of the filtrate and the feed solution, respectively, measured by ultraviolet/visible spectrometry [UV-VIS Spectroscopy (JASCO V-550, Japan)], and the used film is deionized. Water cleaning, in order to complete a cycle, the used film will again measure the pure water flux. The recovery rate ( FR _w,i ,) of the pure water flux in the i-th cycle is calculated by the following formula: In order to calculate the fouling-resistance of the membrane, in the i-th cycle, the flux loss rate (Rt,i) due to total protein fouling is defined as follows: In the i-th cycle, the flux loss rates (Rr,i and Rir,i) due to reversible and irreversible protein fouling are defined as follows:

1. Results and discussion

A. Surface grafting and its properties

The PVDF ultrafiltration membrane is prepared by a wet phase conversion method in which polyethylene glycol is added as a pore former. The comb-like polySBMA is then grafted onto the surface of the ultrafiltration membrane to avoid protein fouling. In order to make the high polarity polySBMA On hydrophobic PVDF surfaces, the PVDF surface must first be activated with ozone, and the comb-like structure of polySBMA is formed by surface-initiated atom transfer radical polymerization (ATRP) polymerization of SBMA monomers.

Referring to the first figure, the surface modification procedure can be divided into three steps: the first step is to produce a peroxide on the surface of the pure PVDF membrane by ozone treatment. The concentration of ozone and its treatment time determine the amount of peroxide groups. The method used is the (DPPH) depletion assay. Approximately 30 minutes of ozone treatment can produce a peroxide group of 2.35 nmol/cm2.

In the second step, the initiator BIEA is grafted onto the PVDF membrane surface and then subjected to a thermally induced polymer polymerization reaction. In this step, the peroxide groups on the ozone treated PVDF membrane will cleave with increasing temperature, and this step is carried out at about 80 ° C for 24 hours. The BIEA grafted onto the film was analyzed by X-ray photoelectron spectroscopy (XPS) to analyze its composition. The XPS core stratigraphic map of C1s and Br3d of PVDF-g-PBIEA membrane is shown in (b)-(c) of the second figure, wherein the XPS core stratigraphic map of C1s contains five map features. The two binding energies, -CH2- and -CF2-, respectively, are 285.9 eV and 290.4 eV, which are related to the chemical structure of PVDF, as shown in (a) of the second figure. The other three characteristic peaks are -CH-, C-O or C-Br and O=C-O binding energies of 284.6 eV, 286.5 eV and 288.8 eV, which are related to the chemical structure of the grafted PBIEA. In addition, the XPS core-level map of Br3d provides a direct evidence that a PBIEA does form a bromine bond at 70.5 ev Br3d5/2 It was further shown that the BIEA was successfully grafted onto the surface of the film.

In the third step, SBMA macromonomers were copolymerized onto the PVDF-g-PBIEA membrane by atom transfer radical polymerization (ATRP). The graft amount of SBMA was determined by the ratio of SBMA to BIEA and the reaction time.

The third step of ATRP is in the presence of the catalyst Cu(I)/bpy, initiated by the bromine of the PVDF-g-PBIEA membrane. Infrared Spectroscopy Measurements The chemical composition of a PVDF film modified with polySBMA can be observed, and its typical characteristic spectrum is shown in the third figure. For the grafted PSBMA, whether the polymer is grafted or not can be judged by the characteristic peaks of the carbon-oxygen double bond (Carbonyl Groups) and the sulfonate group of the ester group (OC=O stretch at 1727 cm-1). And -SO3 stretch at 1033 cm-1), both strengths increase with increasing SBMA concentration (0.019 to 0.187 g/mL).

The measurement of the graft density is based on measuring the weight added by the modified membrane. The fourth graph shows the relationship between the surface graft density and the contact angle at different solution monomer concentrations. As the polymerized polySBMA increases, the contact angle of water decreases. The graft density increased monotonically as the concentration of SBMA increased until the highest value of 0.4 mg/cm2 was reached. In a similar situation, as the SBMA increases, the contact angle of the water slowly decreases to 52°. When the concentration of SBMA is higher than 0.187g/mL, the two curves of PVDF-g-PBIEA-g-PSBMA film will reach the most Good value.

B. Preparation of surface morphology of PVDF film

The surface morphology of the surface-modified film is observed by a scanning electron microscope at a magnification of 10,000 times, as shown in the fifth figure, wherein (a) shows the cross-sectional state of the pure PVDF film, which has The epithelial layer and the finger-shaped giant holes below it. As shown in (b), after ozone treatment, larger pores are formed on the surface of the membrane, presumably due to the ozone etching effect. (c)-(d) shows the morphology of PVDF film grafted with PSBMA at different graft densities. It can be found that when the graft density is 0.19±0.05 mg/cm2, only the membrane is partially covered with PSBMA; When the graft density was increased to 0.4 ± 0.018 mg/cm2, almost all the pores on the film were covered by PSBMA. According to the above SEM photograph, we believe that the stable decrease of the water contact angle is accompanied by an increase in the graft density, and the real reason is that the film is covered by PSBMA instead of the thickness of the PSBMA layer.

C. Protein adsorption

Measurement of protein adsorption has become an important indicator for determining the efficacy of protein filtration procedures. Two major plasma proteins: serum albumin (albumin) and gamma-globulin (gamma-globulin) were tested in this experiment. First, the test membrane is immersed in 1 mg/mL serum albumin (albumin) or γ-globulin (γ-globulin) solution, and the protein adsorbed on the membrane is estimated by measuring the protein concentration floating in the upper layer. . The sixth figure shows the different grafting density The adsorption results of albumin or γ-globulin, all the adsorption experimental data are standardized according to the membrane area. We found that the adsorption amount of either albumin or γ-globulin decreases linearly with increasing graft density, and the slopes of the two are almost the same. Since both albumin and γ-globulin have different surface affinity for pure PVDF, the adsorption amount of γ-globulin is reduced to about 10 μg/cm 2 , and the adsorption amount of albumin can be reduced to 1 μg/cm 2 . It is worth noting that the actual amount of adsorption should be smaller because the adsorption area of the porous material is not only the surface adsorption.

D. Cyclic filtration experiment of bovine serum albumin (BSA)

The PVDF membrane grafted with polySBMA provided by the present invention was subjected to the following cyclic filtration experiment. Before the experiment, filter with pure water until the amount of the filtrate stabilizes first, and determine Jw0. The seventh figure shows the amount of pure water filtrate obtained from PVDF membranes with different grafting densities of polySBMA. We found that when the grafting density is 0.25 mg/cm2, the Jw0 of the modified membrane is higher than the Jw0 of pure PVDF. The reason is that the ozone etching causes the pores of the membrane to become large, and it is also found that Jw0 gradually decreases when the graft density is higher.

Each filtration cycle can be further subdivided into three steps, the first step is protein filtration, the second step is to rinse the filtered membrane with pure water, and the third step is pure water filtration. Referring to the seventh figure, due to the relationship between protein fouling, the amount of filtrate of the BSA solution rapidly decreases at the initial stage until a stable adsorption of the membrane to the protein is obtained, and a stable filtrate amount J _{Pi is obtained} . In order to understand the situation of irreversible membrane fouling, we clean the membrane surface after the protein filtration experiment, and then measure the pure water filtration flux to obtain the two values of J _wi and J _Pi , then calculate the pure water flux recovery rate, Scaling rate, reversible fouling rate and irreversible fouling rate.

The eighth graph shows the various ratios described above for the first cycle of BSA filtration. The total protein fouling ( R _t,i ) is calculated by the formula (4), which represents the filtrate flux loss rate due to membrane surface protein fouling, which in turn contains the protein permanent adsorption membrane surface or temporary The result of adsorbing the membrane surface. If the protein temporarily adsorbs the membrane surface and the amount of filtrate is reduced, the amount of filtrate will be recovered after the membrane is cleaned. Therefore, the reversible fouling ratio ( R _r,i ) is defined as the amount of filtrate in the third step divided by the amount of filtrate reduced by the first step; the remaining unrecoverable filtrate flux is due to permanent adsorption of protein. The result of the membrane surface is defined as the irreversible fouling ratio ( R _ir,i ). The pure water flux recovery ratio ( FR _w,i ) is defined as the pure water flux of the i-th cycle except for the pure water flux of the previous cycle, which is just 1- R _ir,i . Generally, the anti-fouling ability of the membrane is determined by reference to the irreversible fouling rate ( R _ir , _i ) or the pure water flux recovery rate FR _w,i . When the FR _{w,i is} higher, it represents the i-th cycle. The less protein is permanently adsorbed.

Referring to the eighth figure to analyze the first cycle, for the untreated PVDF film, FR _{w,1 was} only 28.3%, but it increased as the graft density increased. When the graft density reached 0.35 mg/cm ² , FR _w,1 suddenly increased significantly, and when the graft density reached 0.4 mg/cm ² , FR _{w,1 was} significantly increased to 88.8%. It can be found that the PVDF film grafted with polySBMA effectively reduces the fouling of the membrane surface, and when the graft density reaches 0.35 mg/cm ² , the PVDF membrane surface is completely covered by polySBMA.

In order to further analyze the fouling of the membrane surface, it was analyzed in the first cycle to summarize the scale ratio R _t,1 and the reversible fouling rate R _r,1 . R _t,1 represents the total effect of fouling on flux loss, which includes reversible and irreversible fouling. It can be found that as the graft density of polySBMA increases, R _t,1 gradually decreases. When the graft density reaches 0.35 mg/cm ² , R _t,1 decreases sharply; when the graft density does not reach 0.35 mg/cm ² , R _{r,1 is} almost maintained at a certain value, and when the graft density reaches 0.4 mg/cm ² , R _{r,1 is} almost reduced to zero. From this, it can be seen that for PSBMA, a graft density of 0.35 mg/cm ² can effectively reduce reversible film surface fouling, and a graft density of 0.4 mg/cm ² can almost completely eliminate reversible film surface fouling. As for the irreversible scale, it is speculated that BSA may be trapped in the pores of the membrane, so similarly, the graft density of 0.35 mg/cm ² has not completely covered the pore wall, and 0.4 mg/cm ² The graft density is almost complete in the pore walls to eliminate irreversible fouling.

E. Circulating filtration experiment of γ-globulin

To further understand the filtration efficiency of PVDF membranes grafted with polySBMA, we continue to discuss the results of the 2nd and 3rd filtration cycles for bovine serum albumin (BSA) and gamma-globulin (γ-globulin) solutions. The ninth graph shows the results of filtration of BSA when the graft density is 0.4 mg/cm ² , and it can be found that the fluxes of the three cycles are almost the same, and after the first cycle, the barrier ratio of the film to BSA is close to the maintenance constant. Conversely, for a pure PVDF membrane, the filtrate flux for the third cycle was significantly lower than for the second cycle, and the barrier rate of BSA for pure PVDF membranes increased gradually at each cycle. The above results can confirm the excellent performance of PVDF- g- polySBMA membrane filtration on BSA solution. We can also find that its blocking rate to BSA is 72%, indicating that BSA molecules continue to pass through the membrane pores without causing further scaling. This phenomenon also indicates that the grafted polySBMA does enter the pores of the membrane, so the fouling condition is effectively controlled in the first cycle.

The tenth graph shows the filtration efficiency of a PVDF membrane grafted with polySBMA to a γ-globulin solution. Unlike the filtration of BSA solution, the filtration results of γ-globulin solution show that γ-globulin scaling continues to occur in either the pure or modified membrane, which results in each filtration cycle. The amount of filtrate is reduced and the blocking rate is increased. The PVDF- g- polySBMA film still performs much better than the pure PVDF film despite the occurrence of continuous fouling. The eleventh figure shows the pure water flux recovery rate of the two membranes. In the first filtration cycle, the pure water flux recovery rate of the pure PVDF membrane is only 18.7%, and the second filtration cycle is 76%, in the third filtration cycle is 79%; in other words, the irreversible fouling rate is 81.3%, 24%, 21% in the first, second, and third cycles, showing that the new formation of γ-globulin is irreversible The amount of adsorption is quite obvious. For the PVDF- g- polySBMA membrane, the pure water flux recovery rate in the first filtration cycle was 74.7%, 91.4% in the second filtration cycle, and 95.3% in the third filtration cycle. The irreversible fouling rates were 25.3%, 8.6%, and 4.7% in the first, second, and third cycles. It can be seen that although the γ-globulin has continuous scaling, the increase of the irreversible adsorption amount is in the first cycle. After the decline significantly. We propose two reasons that may cause continuous scaling: First, the original membrane has a high blocking rate for γ-globulin, resulting in too little γ-globulin entering the pores of the membrane and not reaching adsorption saturation; The partially irreversible γ-globulin is adsorbed on the membrane surface and deformed, so that the γ-globulin in the solution is continuously adsorbed by the deformed region. We speculate that the first cause is more likely to cause continuous scaling. If it is the second reason, γ-globulin will strongly adsorb on the membrane surface, and it is unlikely that it will occur in the third cycle with nearly 100% pure water. Flux recovery rate.

In the above example, the PVDF ultrafiltration membrane was successfully formed by ozone treatment with surface-initiated ATRP grafted amphoteric PSBMA. When the graft density reached 0.4 mg/cm ² , the membrane hardly adsorbed BSA but adsorbed a small amount. Γ-globulin (10μg/cm ² ), the cyclic filtration test for BSA showed perfect anti-fouling properties. In the first cycle, the pure water flux recovery rate reached 88.9%. In the second cycle, pure The water flux recovery rate reaches 100%. A cyclic filtration experiment for gamma-globulin showed a similar situation, but with a small amount of protein adsorption. In the first cycle, the pure water flux recovery rate reached 73.7%. In the third cycle, the pure water flux recovery rate reached 95.5%. The above results show that the protein fouling situation is effectively inhibited by grafting PSBMA. In addition, we believe that the amphoteric PSBMA grafted with the surface-initiated ATRP by ozone treatment also effectively enters the pores of the membrane, so that low fouling characteristics can be achieved.

In addition to protein filtration, the low biofouling filter membrane provided by the present invention can also be applied to a Membrane Bioreactor (MBR). Currently used in combination with wastewater treatment procedures, it has the following advantages: complete removal of solid materials, significant physical disinfection capabilities, excellent removal of organic matter, and solid machine volume without wasting space. However, the fouling situation of MBR often leads to high operating costs and application range limitations. The fouling of MBR is very common and is usually caused by microorganisms. In the early stage of the filtration operation, the microorganisms will first adsorb on the membrane surface, resulting in subsequent continuous adsorption fouling and severe filtration resistance. Therefore, the PVDF ultrafiltration membrane provided by the grafted amphoteric PSBMA provided by the invention can effectively reduce the adsorption of microorganisms. Achieve the purpose of increasing the amount of filtrate.

Obviously, many modifications and variations of the present invention are possible in the light of the scope of the appended claims. It is implemented in other embodiments. The foregoing is only a preferred embodiment of the present invention. The scope of the invention is not intended to limit the scope of the invention, and the equivalents and modifications may be included within the scope of the application.

The first figure is a schematic diagram of the surface copolymerization process of PVDF- g- PBIEA- g- PSBMA ultrafiltration membrane: (a) pure PVDF ultrafiltration membrane is washed with secondary distilled water at 25 °C, (b) at 25 °C pretreatment of PVDF ultrafiltration membrane with isopropanol containing ozone/oxygen mixture, (c) ozone treated PVDF ultrafiltration membrane treated with IPA containing PBIEA giant starter monomer and reacted at 80 °C, (d) The PVDF- g- PBIEA membrane was treated with methanol containing PSBMA macromonomer and reacted at 40 °C; the second graph was analyzed by X-ray photoelectron spectroscopy (XPS) for the core stratigraphic map of C _1s : (a) pure PVDF ultrafiltration membrane, (b) PVDF- g- PBIEA ultrafiltration membrane, (c) core stratigraphy map of PVDF- g- PBIEA ultrafiltration membrane with higher resolution Br _3d ; the third diagram is infrared spectrum: (a ) of pure PVDF membrane, (b) PVDF- g -PBIEA ultrafiltration membrane, (c) a graft density of 0.18mg / cm PVDF- g -polySBMA membrane ^2, (d) grafting density 0.4mg / PVDF- g- polySBMA ultrafiltration membrane of cm ² ; the fourth graph shows the relationship between surface graft density and water contact angle at different monomer concentrations of SBMA solution; the fifth figure shows by scanning electron microscope Zoom in 10,000 times to observe surface modification The surface type of the material: (a) shows the cross-sectional shape of the pure PVDF film, (b) shows the surface morphology of the film after ozone treatment at 25 ° C for 30 minutes, and (c) shows that the PSBMA graft density is 0.18 The surface profile of the PVDF film of mg/cm ² , (d) shows the surface morphology of the PVDF film with a PSBMA graft density of 0.4 mg/cm ² ; the sixth figure shows the different graft density for the albumin or γ-globulin The adsorption result. All membranes were soaked in 5 mL of 0.1 M PBS containing 1 mg/mL BSA or 1 mg/mL γ-globulin solution (pH 7.4) and placed at 37 ° C for 24 hours. The seventh graph shows the different polySBMA grafting density, which changes with time. Flux value. The ultrafiltration experiments were carried out under the conditions of 25 ° C, 1 atm and 300 rpm. The eighth graph shows the different polySBMA graft density versus pure water flux recovery rate in the first cycle of BSA filtration ( FR _{w, 1} ) and other fouling ratios ( R : R _{t, 1} , R _{ir, 1} , and R _{r, 1} ); the ninth figure shows pure when the graft density is 0.4 mg/cm ² Filtration results of PVDF membrane and PVDF- g- polySBMA membrane for BSA: (a) circulating filtrate flux (b) blocking rate, the above experiments were carried out in three cycles at room temperature; the tenth graph shows when grafting When the density is 0.4mg/cm ² , the filtration results of γ-globulin by pure PVDF membrane and PVDF- g -polySBMA membrane: (a) circulating filtrate flux (b) blocking rate, the above experiments are all in the chamber After three cycles of experiments under temperature; and the eleventh figure shows the pure PVDF film and PVDF- g- polySBMA film pair with a graft density of 0.4 mg/cm ² in the i-th cycle (a) BSA (b) Pure γ flux recovery rate of γ-globulin.

Claims (20)

A low biofouling polymer composite film comprising: an activated fluorine-based membrane, wherein the fluorine-containing substrate has a high grafting The molecular grafting density is greater than or equal to 0.3 chains/nm2, and the chain length is greater than or equal to 50 units; a branched polymer layer having a zwitterionic group having a zwitterionic group The branched polymer layer is formed on the fluorine-containing substrate by surface grafting, wherein the zwitterionic group comprises one of the following groups: phosphobetaine, sufobetaine, carboxylbetaine and derivatives thereof . The low-bioscale polymer composite film according to claim 1, wherein the fluorine-containing substrate comprises one of the following groups: polyvinylidene fluoride (PVDF), copolymers of tetrafluoroethylene and perfluoro (propyl vinyl ether), copolymers Of tetrafluoroethylene and perfluoro-2,3-dimethyl-1,3-dioxole, copolymers of tetrafluoroethylene and vinyl fluoride, poly(vinyl fluoride), poly(vinylidene fluoride), polychlorotrifluorethylene, vinyl fluoride/vinylidene fluoride copolymers, and vinylidene fluoride/hexafluoroethylene Copolymers. Such as the low bioscale polymer composite film of claim 1 of the patent scope, wherein the above The fluorine-containing substrate is subjected to activation treatment by ozone. The low biofouling polymer composite film according to claim 1, wherein the surface grafting reaction is a two-step polymerization. As the low biofouling polymer composite film of claim 4, more than or equal to 5 mol% of the halogen-containing monomer is used in the first step. A low biofouling polymer composite film according to claim 5, wherein the halogen-containing single system is 2-(2-bromoisobutyryl)ethyl acrylate or 2-(2-choloisobutyryl)ethyl acrylate. The low bioscale polymer composite film according to claim 5, wherein the second step is Atom Transfer Radical Polymerization (ATRP), and the atom transfer radical polymerization reaction The reaction is initiated by the halogen-containing monomer. For example, in the low bioscale polymer composite film of claim 4, a monomer having a zwitterionic group is used in the second step to form a graft polymer. A low biofouling polymer composite film according to claim 8 wherein the zwitterionic group accounts for more than 10% by weight of the graft polymer. . For example, the low-bioscale polymer composite membrane of the first application patent scope is applied to the following range: separation of protein and peptide, purification of human blood to remove virus or leukocytes. , removal of microorganisms in wastewater (microbial) and preservation of stem cells, pure Purification and concentration. A method for forming a low biofouling polymer composite film, the method for forming the low biofouling polymer composite film comprising: providing a fluorine-containing substrate, wherein a graft density of the graft polymer of the fluorine-containing substrate Greater than or equal to 0.3 chains/nm2, and chain length greater than or equal to 50 units; subjecting the fluorine-containing substrate to an ozone treatment to form a first substrate, wherein the surface of the fluorine-containing substrate reacts with ozone to form a peroxide a first graft polymerization reaction of the first substrate, the first graft polymerization is initiated by a peroxide of the first substrate, and the The first graft polymerization is carried out under a chemical composition comprising at least one functional monomer, wherein the functional monomer comprises at least one acrylate group and at least one halogen functional group, the functional single The system reacts with a peroxide group of the first substrate by an acrylate group, and the functional single system is polymerized with each other by an acrylate group, thereby forming a second substrate having a halogen functional group; And performing the second substrate a second graft polymerization reaction initiated by a halogen functional group of the second substrate, and the second graft polymerization reaction is carried out in a macro-monomer The chemical composition is carried out, wherein the macromonomer comprises at least one acrylate group and at least one zwitterionic group, and the macromono system reacts with the halogen functional group of the second substrate by an acrylate group And the giant single system is condensed by acrylate groups Combining, thereby forming a zwitterionic group grafted low biofouling polymer composite film, wherein the zwitterionic group comprises one of the following groups: phosphobetaine, sufobetaine, carboxylbetaine and derivative. The method for forming a low biofouling polymer composite film according to claim 11, wherein the fluorine-containing substrate comprises one of the following groups: a micro-filtration membrane, an ultrafiltration membrane (ultra) -filtration membrane) with a nano-filtration membrane. The method for forming a low biofouling polymer composite film according to claim 11, wherein the fluorine-containing substrate comprises one of the following groups: polyvinylidene fluoride (PVDF), copolymers of tetrafluoroethylene and perfluoro (propyl vinyl ether) ), copolymers of tetrafluoroethylene and perfluoro-2,3-dimethyl-1,3-dioxole, copolymers of tetrafluoroethylene and vinyl fluoride, poly(vinyl fluoride), poly(vinylidene fluoride), polychlorotrifluorethylene, vinyl fluoride/vinylidene fluoride copolymers, and vinylidene Fluoride/hexafluoroethylene copolymers. A method for forming a low biofouling polymer composite film according to claim 11, wherein the ozone treatment uses an ozone/oxygen mixed fluid. The method for forming a low biofouling polymer composite film according to claim 11, wherein the ozone concentration ranges from about 5 g/m3 to 50 g/m3. The method for forming a low biofouling polymer composite film according to claim 11 wherein the ozone treatment time ranges from about 5 minutes to 60 minutes. The method for forming a low biofouling polymer composite film according to claim 11, wherein the first graft polymerization reaction and the second graft polymerization reaction are atom transfer radical polymerization (Atom Transfer Radical Polymerization). ;ATRP). The method for forming a low biofouling polymer composite film according to claim 11, wherein the first graft polymerization temperature is higher than 70 °C. The method for forming a low biofouling polymer composite film according to claim 11, wherein the functional monomer comprises 2-(2-bromoisobutyryl)ethyl acrylate (BIEA). The method for forming a low biofouling polymer composite film according to claim 11, wherein the macro-monomer is a sulfobetaine acrylate or a sulfonic acid polycondensate. Amine-methyl acrylate [sulfobetaine methacrylate (SBMA)].