Improving the hydrophilic and antifouling properties of poly(vinyl chloride) membranes by atom transfer radical polymerization grafting of poly(ionic liquid) brushes

Abstract

In this study, poly(1-butyl-3-vinylimidazolium bromide) (PBVIm-Br) was grafted onto the poly(vinyl chloride) (PVC) membrane surface via a 2-step atom transfer radical polymerization (ATRP) reaction. Poly(2-hydroxyethylmethacrylate) (PHEMA) was grafted onto the membrane surface by aqueous ATRP reaction; then, BVIm-Br was introduced onto the surface of the PHEMA-modified PVC membrane through traditional ATRP reaction. The analysis of surface chemistry confirmed the successful grafting of PHEMA and PBVIm-Br on PVC membrane surface, and the grafting density (GD) of PBVIm-Br gradually increased as the grafting time was prolonged. The modified membrane exhibited a positive charge and significantly enhanced surface hydrophilicity. The static water contact angle of the membrane surface decreased from 92.3°to 51.6°as the GD of the PBVIm-Br brushes increased. Filtration experiments indicated that the water flux of the modified membrane increased with increasing GD, and their recovered fluxes were more than twice than the original. In addition, the total fouling ratio of the membranes decreased from 89% in M0 to 67% in M5, and most of the fouling was reversible as the GD of PBVIm-Br brushes increased.These results indicated that the positive charged poly(ionic liquid) brushes featuring hydrophilic properties would have potential applications in membrane separation. KEYWORDS | Preparation of PVC membranesPoly(vinyl chloride) membranes were prepared using classical immersion precipitation method. | ATRP grafting of poly(ionic liquid) brushes onto PVC membranesThe grafting process includes 2 steps, which are shown in Figure 1. | Membrane characterizationThe chemical compositions of the membranes were characterized by The morphologies of the membranes were observed via scanning electron microscopy (SEM; Phenom G2 pro, Holland). Samples were fractured in liquid nitrogen to obtain orderly cross sections and then sputter coated with gold before SEM observation.The zeta potentials of the membranes were measured through a streaming potential method using an electro kinetic analyzer (SurPASS Anton Paar, GmbH, Austria). The pH of the solution was adjusted by adding NaOH or HCl solution, and the measurement was performed at 25°C.The water CAs of the membranes were measured with a data physics instrument (OCA20, Dataphysics, Germany) under a sessile drop model at room temperature, and the instrument was equipped with a camera to capture images. | Grafting densityThe final grafted PVC membranes were thoroughly washed in DI water and then dried in a vacuum oven at 55°C to constant weight; the grafting density (GD) (μg/cm 2 ) of the grafted membrane was calculated as follows 28:where W is the weight of the PVC grafted membrane (g), W 0 is the weight of the previous membranes before grafting (g), and A is the area of the membrane (m 2 ). | Filtration propertiesThe filtration properties of the membranes were examined using a vacuum filter apparatus. A piece of each test membrane (separation area of 3.46 cm 2 ) was fixed between the top ...

Recent advances in bio-inspired ionic liquid-based interfacial materials from preparation to application

“…ATRP has been widely used in the preparation of modified IL membranes due to its strong controllability. For example, Figure 2A shows that Cheng et al (2018) grafted poly(1-butyl-3-vinylimidazolium bromide) (PBVIm-Br) onto the surface of poly(vinyl chloride) (PVC) membrane by ATRP. The hydrophilicity of the poly(ionic liquid) (PIL) polymer brush-modified membrane is significantly enhanced by positive charge, which has a potential application in membrane separation.…”

Antibiofouling Polyvinylidene Fluoride Membrane Functionalized by Poly(ionic liquid) Brushes via Atom Transfer Radical Polymerization

“…In addition, PILs have particular appeal in new antibacterial materials because of their tunable molecular design properties; by using strategic ionic compositions in synthesis, the PIL can be designed with various structures to solve specific problems. , Currently, PILs have been successfully used in antifouling, high-temperature proton exchange, gas penetration, counterion exchange, and antibacterial materials, , but the application in membrane filtration is relatively rare. Cheng et al grafted hydrophilic IL on the membrane’s surface to improve the performance against organic fouling . There is no study on fixing the antibacterial IL on the membrane surface to mitigate biofouling in the filtration process.…”

“…Cheng et al grafted hydrophilic IL on the membrane's surface to improve the performance against organic fouling. 42 There is no study on fixing the antibacterial IL on the membrane surface to mitigate biofouling in the filtration process. By introducing the PIL brushes with antibacterial and tunable properties to the surface, the antibiofouling performance of the membrane can be adjusted and improved for potential real-world use in a functional membrane material system.…”

Hydrophilic and Positively Charged Polyvinylidene Fluoride Membranes for Water Treatment with Excellent Anti-Oil and Anti-Biocontamination Properties

“…Polyionic liquids, also known as polymer ionic liquids [21], have been reported to improve the hydrophilicity of membranes and charge the membranes, so they are quite applicable in solving the membrane fouling problem [22,23]. Many of these zwitterions have been employed as polymer brushes to modify the surface of materials with enhanced hydrophilicity and antifouling ability [24,25].…”