Facile Fabrication, Structure, and Applications of Polyvinyl Chloride

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Facile Fabrication, Structure, and Applications of Polyvinyl Chloride Mesoporous Membranes Nan Nan Guo, Qiu Gen Zhang,* Hong Mei Li, Xin Mei Wu, Qing Lin Liu, and Ai Mei Zhu Department of Chemical & Biochemical Engineering, College of Chemistry & Chemical Engineering, Xiamen University, Xiamen 361005, China ABSTRACT: Mesoporous polymer membranes are important in various separation processes and have become more crucial with increasing concerns in environment protection. Here, we report novel mesoporous membranes of polyvinyl chloride (PVC) nanofibers prepared via a modified freeze-extraction technique. The as-prepared nanofibers have an average diameter of ∼45 nm and are dispersed heterogeneously in an ethanol solution. The nanofiber formation is studied in detail. The resulting nanofiber dispersion is directly filtered on a macroporous support to fabricate mesoporous membranes. The as-fabricated membranes have a controllable thickness ranging from 360 nm to 1055 nm, and a high porosity up to 63% that is at least 5 times greater than that of most of the commercial ultrafiltration membranes. These membranes present an ultrahigh water flux up to 6612 L m−2 h−1 bar−1 and a good ferritin rejection during ultrafiltration. Moreover, these membranes show a fast and high-efficient absorption for Methylene Blue (MB). The newly developed mesoporous membranes have a great potential application in various separation processes. membranes, such as carbon nanotubes,18,19 carbonaceous nanofibers, and metal oxide nanofibers.20,21 The resulting membranes show a great potential in ultrafiltration processes. In the past decades, electrospun polymer nanofibers are widely used to prepare membranes with pore size ranging from tens of nanometers to several micrometers.22,23 These nanofibers have diameters in the micrometer or submicrometer range; thus, it is difficult to fabricate a mesoporous membrane with a pore size below 20 nm. Besides, the electrospun nanofibers have a drawback: poor diameter control and difficulty in fabricating thin films. Other methods have been reported to prepare polymer nanofibers; however, it is usually difficult to fabricate meosporous membranes, because of the intricate operations and specific outcome, such as molecular self-assembly, lithography, template synthesis, and interfacial polymerization.24−27 In this work, we report novel mesoporous membranes of polyvinyl chloride (PVC) nanofibers, showing an ultrahigh water flux and good separation performance during ultrafiltration. PVC, which is a polymer synthesized from vinyl chloride, is one of the most widely used polymer materials to fabricate ultrafiltration and microfiltration membranes, because of its outstanding properties, such as robust mechanical strength, low-cost, and high resistance to acids, alkalis, solvents, and chlorine.28−30 Moreover, PVC membranes can maintain a long life and remain intact after repeated cleaning with a wide variety of chemical agents. However, the PVC membranes prepared by the traditional nonsolvent-induced phase separation process usually show a low permeation flux of 100 L m−2 h−1 bar−1.29,30 Here, we report a facile approach to fabricate a highly

1. INTRODUCTION Mesoporous materials, with pore sizes between 2 nm and 50 nm, have attracted widespread attention in various fields, including environmental energy, adsorption, separation, drug delivery, catalysis, and sensors.1−5 These materials present various morphologies, because of their controllable composition and structure such as monoliths, spheres, rods, fibers, and membranes.1,6 Of those, mesoporous membranes are used in ultrafiltration for water treatment, food industry, and life science, and have become more crucial with increasing concerns in the living environment.7−9 Currently, mesoporous polymer membranes are mainly made by a non-solvent-induced phase separation process. The as-formed membranes usually have a thick separation layer with a low porosity (generally below 10%), leading to a low permeation flux.10,11 Thin-film composite membranes involving a thin separation layer on a submicrometer porous support generally show an ultrahigh permeation flux during pressure-driven filtration.12,13 For example, the membrane with a ∼0.85 μm-thick chemically cross-linked poly(vinyl alcohol) layer has a water flux that is 5 times higher than that of the commercial PAN10 membrane.14 The membrane with a ∼0.15-μm-thick cross-linked poly(4vinylpyridine) layer has a water flux of 583 L m−2 h−1 bar−1 and a good rejection for cytochrome c.15 The membrane with a ∼0.35 μm-thick cellulose layer has a permeation flux that is significantly higher (∼10 times) than that of the commercial ultrafiltration membranes for separation of oil/water emulsions.16 By this time, there is a continuous demand for a practical approach to fabricate highly permeable mesoporous membranes using commercial polymers. Recently, one-dimensional nanomaterials including nanofibers, nanowires, and nanotubes have attracted increasing interest and are used to fabricate highly permeable thin-film composite membranes, because of their peculiar properties.17−21 Particularly, one-dimensional inorganic materials have been applied to fabricate highly permeable mesoporous © 2014 American Chemical Society

Received: Revised: Accepted: Published: 20068

October 9, 2014 December 2, 2014 December 5, 2014 December 8, 2014 dx.doi.org/10.1021/ie503986h | Ind. Eng. Chem. Res. 2014, 53, 20068−20073

Industrial & Engineering Chemistry Research

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Figure 1. Morphology of PVC nanofibers: TEM images of the PVC nanofibers made using (a) DMAC, (b) NMP, and (c) DEC as the solvent; SEM images of the PVC nanofibers made using (d) DMAC, (e) NMP, and (f) DEC as the solvent. The SEM samples were prepared by filtering 8 mL of the nanofiber dispersion on a PC filter. The scale bar is 100 and 500 nm for the TEM and SEM images, respectively.

dispersion was filtered across a polycarbonate (PC) filter placed on a glass filter holder at a suction vacuum pressure of 80 kPa. During the filtration, the PVC nanofibers were freely deposited on the PC filter to form a PVC mesoporous membrane. The membrane thickness was controlled by adjusting the volume of the nanofiber dispersion filtered. 2.3. Ultrafiltration Experiments. Ultrafiltration experiments were performed using a glass filter holder at a suction vacuum pressure of 80 kPa. The pure water flux (J, expressed in units of L m−2 h−1 bar−1) was evaluated by filtering 100 mL of ultrapure water across a membrane, and was calculated by

permeable mesoporous membrane with a thin PVC nanofiber layer. The nanofibers with an average diameter of ∼45 nm are formed via the modified freeze-extraction technique and uniformly dispersed in an ethanol solution. The nanofiber formation was investigated in detail. The as-fabricated membranes have a controllable thickness (ranging from 360 nm to 1055 nm) and a high porosity (up to 63%). These membranes show great potential application in wastewater treatment. They have an ultrahigh water flux (up to 6612 L m−2 h−1 bar−1) and a good rejection for ferritin during ultrafiltration, and they show fast and high-efficient absorption for Methylene Blue (MB).

J=

2. EXPERIMENTAL SECTION 2.1. Materials. PVC with a weight-based molecular weight of Mw ≈ 43 000 and a number-based molecular weight of Mn ≈ 22 000, ferritin (from equine spleen) and MB were purchased from Sigma−Aldrich. Solvents including N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone (NMP), and 1,2dichloroethane (DEC), of analytical grade, were obtained from Sinopharm Chemical Reagent Co. Ltd. (China). Polycarbonate (PC) filters (0.2 μm cutoff, 25 mm in diameter) were purchased from Toyo Roshi Kaisha, Ltd. (Japan). 2.2. Fabrication of PVC Mesoporous Membranes. PVC nanofibers were prepared via the modified freeze-extraction process. Typically, a 0.1 mg mL−1 PVC solution was prepared by dissolving PVC powders in a solvent (DEC, DMAC, or NMP) at 40 °C, and was purified using a syringe filter (0.45 μm pore) to obtain homogeneous transparent solutions. Ten grams (10 g) of the PVC solution was rapidly frozen in liquid nitrogen contained in a 250-mL beaker, subsequently 90 g of ethanol (−40 °C) was added and the contents were then transferred to a refrigerator at −40 °C for 24 h. The resulting freeze-extracted solution was the expected PVC nanofiber dispersion. The mesoporous membranes were fabricated by a direct filtration process. A desired volume of the PVC nanofiber

V AtP

(1)

where V is the water volume (L), A the effective membrane filtration area (m2), t the filtration time (h), and p the suction pressure across the membrane (bar). To evaluate separation properties of the as-fabricated membranes, the ferritin rejection was measured by filtering a 60 μg mL−1 ferritin solution across the membrane. The feed, the filtrate, and the concentrate were characterized by an ultraviolet and visible (UV-vis) spectrophotometer (Model UV1800 series, Shimadzu, Japan). The rejection (R) was calculated by ⎛ C − Ci ⎞ R (%) = ⎜ 0 ⎟ × 100 ⎝ C0 ⎠

(2)

where Ci and C0 is the ferritin concentration in the filtrate and the feed, respectively. 2.4. Adsorption Measurements. MB was used to evaluate the adsorption properties of the membranes. A desired volume of a 5 μg mL−1 MB solution was filtered through the PVC mesoporous membrane at a suction vacuum pressure of ∼2 kPa. The membrane was fabricated by filtering 80 mL of the PVC nanofiber dispersion on a PC support. The MB concentration in the feed and the filtrate was measured by 20069

dx.doi.org/10.1021/ie503986h | Ind. Eng. Chem. Res. 2014, 53, 20068−20073


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the UV-vis spectrophotometer. The adsorption rate (Re, %) is the same as the rejection calculation mentioned above. The adsorption capacity (Qe) is calculated by (C − Ci)V0 Qe = 0 m

Table 1. Viscosities of the PVC Solutions Using Different Solvents at 25 °C

(3)

where V0 is the feed volume, m is the weight of the PVC membrane, and C0 and Ci are the MB concentrations in the feed and the filtrate, respectively. 2.5. Characterizations. The PVC nanofiber structure was characterized by transmission electron microscopy (TEM) (Model JEM-1400, JEOL, Japan, at 100 kV). The sample was prepared by depositing the nanofiber dispersion dropwise on a copper grid coated with a carbon film. Meanwhile, the morphology of the PVC nanofibers and the mesoporous membranes was observed by scanning electron microscopy (SEM) (Model S4800, Hitachi, Japan). To prevent charging and improve the membrane conductivity, all of the samples were coated with a platinum layer ∼5 nm thick, using a JFC1600 autofine coater before observation. The samples for crosssectional observation were prepared by freeze-fracturing in liquid nitrogen. Besides, the membranes were characterized by X-ray diffraction (XRD) (Model Ultima IV X-ray diffractometer, Rigaku, Japan). The static water contact angle was measured using an optical instrument (Model SL 200B, Shanghai, China) via the pendant drop method at 25 °C with 65% relative humidity.

solution

ηr

ηsp

η0

η

PVC/DMAC PVC/NMP PVC/DEC

1.03 1.09 1.02

0.03 0.09 0.02

0.92 1.65 0.84

0.95 1.80 0.86

25 °C. The viscosity (η0) of DMAC is 0.92 cP, whereas NMP is 1.65 cP. The specific viscosity (ηsp) of the PVC solution with the corresponding pure solvent reflects the internal friction effect of the polymer and polymer, the polymer and the pure solvent. The ηsp, using NMP as the solvent, is ∼3 times greater than that using DMAC, and thus the PVC chains are more difficult to move and stretch in NMP solution than in DMAC solution, leading to the simultaneous formation of large nanoparticles and spindly nanofibers, as shown in Figure 1e. Furthermore, the PVC nanofibers made using DMAC are uniform and can be easily deposited to form an ultrathin freestanding mesoporous layer on the macroporous support (see Figure 1d). To make the nanofiber structure more intuitive, the diameters of the PVC nanofibers made using DMAC were analyzed by the software of Nano Measurer, as shown in Figure 2a. The nanofibers are uniform and have an average diameter of ∼45 nm. The PVC nanofiber microstructure was also studied by XRD. As shows in Figure 2b, a typical peak appeared at ∼24.1° in the spectrum of original PVC and disappeared in the as-prepared PVC nanofibers. This suggests that the as-prepared PVC nanofibers are amorphous materials. Besides, a typical peak at ∼17.5° for the PC support reduced in intensity, because of the coverage of a PVC nanofiber layer. 3.2. Fabrication and Properties of PVC Mesoporous Membranes. An important application of nanofibers is to prepare highly porous membranes or scaffolds.17,20 As mentioned above, DMAC as the solvent would produce uniform PVC nanofibers that are easily used to form a homogeneous mesoporous layer on a porous support. Thus, PVC mesoporous membranes were fabricated by the direct filtration technique in this work. Figure 3 shows the SEM images of the as-fabricated PVC membranes. Clearly, these membranes contain two distinct layers, i.e., the PVC mesoporous layer and the macroporous PC support. The membrane thickness can be easily controlled by varying the volume of the nanofiber dispersion used. The thickness increases almost linearly in the range of 360−1055 nm with the nanofiber dispersion used (see Figure 4). The PVC layer is highly porous from the top-view and crosssectional SEM images. The porosity (P) is estimated by

3. RESULTS AND DISCUSSION 3.1. Preparation and Structure of PVC Nanofibers. As described above, the PVC nanofibers were prepared via the modified freeze-extraction process. The 0.1 mg mL−1 PVC solution was prepared by dissolving PVC powders in a good solvent, and rapidly frozen in liquid nitrogen and then immersed into an ethanol bath at −40 °C to fulfill the extraction process. Three solvents with melting point above −40 °C were used to dissolve PVC to investigate the effect of solvent on the nanofiber formation, i.e., DMAC (melting point of −20 °C), NMP (−24.4 °C) and DEC (−35.3 °C). The resulting colorless and transparent solution was the desirable PVC nanofiber dispersion. Figure 1 shows TEM and SEM images of the as-prepared PVC nanofibers. Clearly, the PVC nanofiber was produced successfully and looked like a string of nanobeads. The solvent played an important role in the nanofiber formation. It is noted that spindly nanofibers were formed using DMAC (Figures 1a and 1d), irregular nanofibers were formed using NMP (Figure 1b and 1e), and inhomogeneous nanofibers were formed using DEC (Figure 1c and 1f). This may be due to the differences in viscosity and solubility parameter of solvents. With a similar solubility (20.3 MPa1/2) to PVC (19.8 MPa1/2),31 DEC is the best solvent and, therefore, produced the finest nanofibers. However, these nanofibers easily aggregated to form an inhomogeneous membrane on a porous support (Figure 1f). DMAC and NMP have the solubility parameters of 22.9 and 22.7 MPa1/2,31 and produce the nanofibers thicker than those using DEC. Interestingly, uniform nanofibers were formed using DMAC, whereas large nanoparticles appeared using NMP. This is resulted from the difference in solvent viscosity. Table 1 lists the viscosities of the pure solvent (η0) and the PVC solution (η), the relative viscosity (ηr), and the specific viscosity (ηsp) at

P=

Vm − Vp Vm

(4)

where Vm is the membrane volume, and Vp is the actual volume of PVC nanofibers and resulted from the mass of PVC nanofibers divided by its density. As shown in Figure 4, the membranes have a high porosity that increased with the nanofiber dispersion used. Typically, the 1055-nm-thick membrane prepared from 16 mL of the nanofiber dispersion has the highest porosity63%, which is at least 5 times greater than that of the skin layer of the most commercial polymer ultrafiltration membranes.11 It is expected that the as-fabricated membranes should have an ultrahigh permeation flux during the pressure-driven filtration. 20070



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Figure 2. Structure of the PVC nanofibers made using DMAC: (a) the nanofiber diameter distribution and (b) XRD spectra of original PVC (black), a PC support (blue), and a PVC nanofiber layer covered on the PC support (red).

Figure 5. Static contact angles of (a) water and (b) cyclohexane on the surface of the 637-nm-thick membrane.

absorbed by the membrane. This suggests that the as-fabricated membranes are highly hydrophobic and superoleophilic, and thus have a great potential for oily wastewater treatment. 3.3. Ultrafiltration Performance of PVC Mesoporous Membranes. To evaluate the separation performance of the PVC mesoporous membranes, the pure water flux and ferritin rejection were measured under neutral conditions, as shown in Figure 6a. These membranes have an ultrahigh water flux that greatly decreases from 6612 L m−2 h−1 bar−1 to 3967 L m−2 h−1 bar−1 with increasing membrane thickness, which is consistent with the filtration theory. Ferritin, which is a ubiquitous intracellular protein, has a diameter of ∼12 nm. The membranes also have a good ferritin rejection that increases with the membrane thickness, and have the highest ferritin rejection of 86.7% for the 1055-nm-thick membrane. Figure 6b shows the UV-vis spectra of ferritin solutions separated by the 637-nm-thick membrane. A rejection of 81.6% was calculated based on the ferritin concentration in the filtrate, and a rejection of 80.6% was calculated from the concentrate. This suggests that the membranes have a good fouling resistance, which is expected in protein separation via ultrafiltration. From these results, the as-prepared membranes will have a great potential for superfast filtration. 3.4. Methylene Blue (MB) Adsorption Using the PVC Mesoporous Membranes. The mesoporous membrane, as a type of highly porous materials, was often used to separate and remove pollutants from wastewaters via adsorption. In this work, the as-prepared PVC membranes were used to adsorb MB from its wastewater, because of their high porosity. MB is one of the most used chemicals for dying cotton, wood, and silk, and it may cause permanent injury to the eyes of humans and animals. The absorption experiment was performed by filtering a given volume of a 5 μg mL−1 MB solution across the

Figure 3. SEM images of the PVC mesoporous membranes: (a) top view of the membrane prepared from 12 mL of the nanofiber dispersion, (b) cross-section of the membrane prepared from 12 mL of the nanofiber dispersion, (c) top view of the membrane prepared from 14 mL of the PVC nanofiber dispersion, and (d) cross-section of the membrane prepared from 14 mL of the PVC nanofiber dispersion. For each image, the scale bar is 500 nm.

Figure 4. Relationship between the membrane thickness and porosity with the volume of the PVC nanofiber dispersion used to prepare the mesoporous membranes.

The superhydrophobicity is one of the important properties of PVC materials.32 The static contact angles of the PVC mesoporous membranes were measured, as shown in Figure 5. The static contact angle of water was 123° for the 637-nm-thick membrane, whereas cyclohexane immediately spread and was 20071



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Figure 6. Separation performance of the PVC mesoporous membranes: (a) pure water flux and ferritin rejection for separating a 60 μg mL−1 ferritin solution, and (b) UV-vis spectra of the feed, the filtrate, and the concentrate for separating a 60 μg mL−1 ferritin solution using the 637-nm-thick membrane.

Figure 7. MB adsorption using the PVC mesoporous membrane: (a) UV-vis spectra of the feed and the filtrate for filtering a 5 μg mL−1 MB solution across the membrane, and (b) plot of the adsorption rate and adsorption capacity of MB by the membrane.

membrane prepared from 80 mL of the PVC nanofiber dispersion. Figure 7 shows adsorption properties of the as-fabricated membrane for MB. It is noted that MB was rapidly adsorbed during the feed flowing through the membrane. The MB concentration in the filtrate is much less than that in the feed when a small amounts of MB solution was treated, and gradually increased and equaled to the value in the feed (Figure 7a). The adsorption rate is high (up to 97.4% for 3 mL of the MB solution filtered) and greatly decreases with increasing volume of the MB solution filtered. The adsorption capacity was also evaluated, and it increased with the feed volume treated and then reached a constant value. The membrane has a high adsorption capacity above 75.9 mg g−1 (mass of MB per 1 g of the PVC nanofibers). Therefore, the as-fabricated membranes should have a great potential in wastewater treatment as highly efficient adsorption materials.

controllable thickness, ranging from 360 nm to 1055 nm, and a high porosity of up to 63%, which is at least 5 times greater than that of most of commercial ultrafiltration membranes. They show high hydrophobicity and superoleophilicity, which are essential to separation membranes for oily wastewater treatment. Moreover, they have present an ultrahigh water flux up to 6612 L m−2 h−1 bar−1 and a good ferritin rejection during ultrafiltration, as well as fast and high-efficient absorption for Methylene Blue (MB). The newly developed mesoporous membranes have a great potential in various separation processes.

4. CONCLUSIONS In summary, we have reported novel mesoporous membranes composed of a thin PVC nanofiber layer and a macroporous support. The PVC nanofibers were prepared using the modified freeze-extraction technique. The solvents play an important role in the nanofiber formation. The PVC nanofibers made using N,N-dimethylacetamide (DMAC) as the solvent are uniform and have an average diameter of ∼45 nm. They were easily deposited to form a thin mesoporous layer on the macroporous support. The resulting mesoporous membranes have a

ACKNOWLEDGMENTS The research was supported by National Nature Science Foundation of China Grant (No. 21306155), the Research Fund for the Doctoral Program of Higher Education (No. 20120121120013), and the Fundamental Research Funds for the Central Universities (No. 2012121029).

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■ ■

REFERENCES

(1) Yamauchi, Y.; Suzuki, N.; Radhakrishnan, L.; Wang, L. Breakthrough and future: Nanoscale controls of compositions,

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morphologies, and mesochannel orientations toward advanced mesoporous materials. Chem. Rec. 2009, 9, 321. (2) Kumar, P.; Guliants, V. V. Periodic mesoporous organic− inorganic hybrid materials: Applications in membrane separations and adsorption. Microporous Mesoporous Mater. 2010, 132, 1. (3) Torney, F.; Trewyn, B. G.; Lin, V. S. Y.; Wang, K. Mesoporous silica nanoparticles deliver DNA and chemicals into plants. Nat. Nanotechnol. 2007, 2, 295. (4) Su, F.; Zeng, J.; Bao, X.; Yu, Y.; Lee, J. Y.; Zhao, X. S. Preparation and characterization of highly ordered graphitic mesoporous carbon as a Pt catalyst support for direct methanol fuel cells. Chem. Mater. 2005, 17, 3960. (5) Shimizu, Y.; Jono, A.; Hyodo, T.; Egashira, M. Preparation of large mesoporous SnO2 powder for gas sensor application. Sens. Actuators, B 2005, 108, 56. (6) Yang, Z.; Lu, Y.; Yang, Z. Mesoporous materials: tunable structure, morphology and composition. Chem. Commun. 2009, 17, 2270. (7) Boissiere, C.; Martines, M. A.; Kooyman, P. J.; de Kruijff, T. R.; Larbot, A.; Prouzet, E. Ultrafiltration membrane made with mesoporous MSU-X silica. Chem. Mater. 2003, 15, 460. (8) Wang, Z.; Yao, X.; Wang, Y. Swelling-induced mesoporous block copolymer membranes with intrinsically active surfaces for sizeselective separation. J. Mater. Chem. 2012, 22, 20542. (9) Jiang, F.; Li, H.; Di, Z.; Sui, S.; Yu, Q.; Zhang, J. Silica ultrafiltration membrane with tunable pore size for macromolecule separation. J. Membr. Sci. 2013, 441, 25. (10) Baker, R. W. Membrane Technology and Applications; John Wiley & Sons, Ltd.: Chichester, England, 2004; Ch. 3. (11) Cuperus, F. P.; Smolders, C. A. Characterization of UF membranes: Membrane characteristics and characterization techniques. Adv. Colloid Interfaces 1991, 34, 135. (12) Karan, S.; Wang, Q.; Samitsu, S.; Fujii, Y.; Ichinose, I. Ultrathin free-standing membranes from metal hydroxide nanostrands. J. Membr. Sci. 2013, 448, 270. (13) Striemer, C. C.; Gaborski, T. R.; McGrath, J. L.; Fauchet, P. M. Charge- and size-based separation of macromolecules using ultrathin silicon membranes. Nature 2007, 445, 749. (14) Ma, H.; Yoon, K.; Rong, L.; Shokralla, M.; Kopot, A.; Wang, X.; Fang, D.; Hsiao, B. S.; Chu, B. Thin-film nanofibrous composite ultrafiltration membranes based on polyvinyl alcohol barrier layer containing directional water channels. Ind. Eng. Chem. Res. 2010, 49, 11978. (15) Wang, Q.; Samitsu, S.; Ichinose, I. Ultrafiltration membranes composed of highly cross-linked cationic polymer gel: The network structure and superior separation performance. Adv. Mater. 2011, 23, 2004. (16) Ma, H.; Yoon, K.; Rong, L.; Mao, Y.; Mo, Z.; Fang, D.; Hollander, Z.; Gaiteri, J.; Hsiao, B. S.; Chu, B. High-flux thin-film nanofibrous composite ultrafiltration membranes containing cellulose barrier layer. J. Mater. Chem. 2010, 20, 4692. (17) Peng, X.; Jin, J.; Ericsson, E. M.; Ichinose, I. General method for ultrathin free-standing films of nanofibrous composite materials. J. Am. Chem. Soc. 2007, 129, 8625. (18) Brady-Estévez, A. S.; Kang, S.; Elimelech, M. A single-walledcarbon-nanotube filter for removal of viral and bacterial pathogens. Small 2008, 4, 481. (19) Srivastava, A.; Srivastava, O. N.; Talapatra, S.; Vajtai, R.; Ajayan, P. M. Carbon nanotube filters. Nat. Mater. 2004, 3, 610. (20) Liang, H. W.; Wang, L.; Chen, P. Y.; Lin, H. T.; Chen, L. F.; He, D.; Yu, S. H. Carbonaceous nanofiber membranes for selective filtration and separation of nanoparticles. Adv. Mater. 2010, 22, 4691. (21) Ke, X. B.; Zhu, H. Y.; Gao, X. P.; Liu, J. W.; Zheng, Z. F. Highperformance ceramic membranes with a separation layer of metal oxide nanofibers. Adv. Mater. 2007, 19, 785. (22) Gopal, R.; Kaur, S.; Ma, Z.; Chan, C.; Ramakrishna, S.; Matsuura, T. Electrospun nanofibrous filtration membrane. J. Membr. Sci. 2006, 281, 581.

(23) Kaur, S.; Gopal, R.; Ng, W. J.; Ramakrishna, S.; Matsuura, T. Next-generation fibrous media for water treatment. MRS Bull. 2008, 33, 21. (24) Huang, J.; Kaner, R. B. A general chemical route to polyaniline nanofibers. J. Am. Chem. Soc. 2004, 126, 851. (25) Palmer, L. C.; Stupp, S. I. Molecular self-assembly into onedimensional nanostructures. Acc. Chem. Res. 2008, 41, 1674. (26) Pisignano, D.; Maruccio, G.; Mele, E.; Persano, L.; Benedetto, F. D.; Cingolani, R. Polymer nanofibers by soft lithography. Appl. Phys. Lett. 2005, 87, 123109. (27) Demirel, G. B.; Buyukserin, F.; Morris, M. A.; Demirel, G. Nanoporous polymeric nanofibers based on selectively etched PS-bPDMS block copolymers. ACS Appl. Mater. Interfaces 2011, 4, 280. (28) Liu, J.; Su, Y.; Peng, J.; Zhao, X.; Zhang, Y.; Dong, Y.; Jiang, Z. Preparation and performance of antifouling PVC/CPVC blend ultrafiltration membranes. Ind. Eng. Chem. Res. 2012, 51, 8308. (29) Fan, X.; Su, Y.; Zhao, X.; Li, Y.; Zhang, R.; Zhao, J.; Jiang, Z.; Zhu, J.; Ma, Y.; Liu, Y. Fabrication of polyvinyl chloride ultrafiltration membranes with stable antifouling property by exploring the pore formation and surface modification capabilities of polyvinyl formal. J. Membr. Sci. 2014, 464, 100. (30) Liu, B.; Chen, C.; Zhang, W.; Crittenden, J.; Chen, Y. Low-cost antifouling PVC ultrafiltration membrane fabrication with Pluronic F127: Effect of additives on properties and performance. Desalination 2012, 307, 26. (31) Bowino, A.; Capannelli, G.; Munari, S.; Turturro, A. Solubility parameters of poly(vinylidene fluoride). J. Polym. Sci. B: Polym. Phys. 1988, 26, 785. (32) Li, X.; Chen, G.; Ma, Y.; Feng, L.; Zhao, H.; Jiang, L.; Wang, F. Preparation of a super-hydrophobic poly(vinyl chloride) surface via solvent−nonsolvent coating. Polymer 2006, 47, 506.

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