Facile surface modification of PVDF microfiltration membrane by strong physical adsorption of amphiphilic copolymers

To endow the surface of poly(vinylidene fluoride) (PVDF) microfiltration (MF) membranes with hydrophilicity and antifouling property, physical adsorption of amphiphilic random copolymers of poly(ethylene glycol) methacrylate (PEGMA) and poly(methyl methacrylate) (PMMA) (P(PEGMA‐r‐MMA)) onto the PVDF membrane was performed. Scanning electron microscopy (SEM) images showed that the adsorption process had no influence on the membrane structure. Operation parameters including adsorption time, polymer concentration, and composition were explored in detail through X‐ray photoelectron spectroscopy (XPS), static water contact angle (CA), and water flux measurements. The results demonstrated that P(PEGMA‐r‐MMA) copolymers adsorbed successfully onto the membrane surface, and hydrophilicity of the PVDF MF membrane was greatly enhanced. The antifouling performance and adsorption stability were also characterized, respectively. It was notable that PVDF MF membranes modified by facile physical adsorption of P(PEGMA₅₈‐r‐MMA₃₃) even showed higher water flux and better antifouling property than the commercial hydrophilic PVDF MF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3112–3121, 2013     

Surface immobilization of polymer brushes onto porous poly(vinylidene fluoride) membrane by electron beam to improve the hydrophilicity and fouling resistance

Poly(vinylidene fluoride) (PVDF) membrane was pre-irradiated by electron beam, and then poly(ethylene glycol) methyl ether methacrylate (PEGMA) was grafted onto the membrane surface in the aqueous solution. The degree of grafting was significantly influenced by the pH value of the reaction solution. The surface chemical changes were characterized by the Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Combining with the analysis of the nuclear magnetic resonance proton and carbon spectra (¹H NMR and ¹³C NMR), PEGMA was mainly grafted onto the membrane surface. Morphological changes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The porosity and bulk mean pore size changes were determined by a mercury porosimeter. The surface and bulk hydrophilicity were evaluated on the basis of static water contact angle, dynamic water contact angle and the dynamic adsorption process. Furthermore, relative high permeation fluxes of pure water and protein solution were obtained. All these results demonstrate that both hydrophilicity and fouling resistance of the PVDF membrane can be improved by the immobilization of hydrophilic comb-like polymer brushes on the membrane surface.     

Amphiphilic poly(vinyl chloride)‐g‐poly[poly(ethylene glycol) methylether methacrylate] copolymer for the surface hydrophilicity modification of poly(vinylidene fluoride) membrane

In this study, a comblike amphiphilic graft copolymer containing poly(vinyl chloride) (PVC) backbones and poly(oxyethylene methacrylate) [poly(ethylene glycol) methylether methacrylate (PEGMA)] side chains was facilely synthesized via an atom transfer radical polymerization method. Secondary chlorines in PVC were used as initial sites to graft a poly[poly(ethylene glycol) methylether methacrylate] [P(PEGMA)] brush. The synthesized PVC‐g‐P(PEGMA) graft copolymer served as an efficient additive for the hydrophilicity modification of the poly(vinylidene fluoride) (PVDF) membrane via a nonsolvent‐induced phase‐inversion technique. A larger pore size, higher porosity, and better connectivity were obtained for the modified PVDF membrane; this facilitated the permeability compared to the corresponding virgin PVDF membrane. In addition, the modified PVDF membrane showed a distinctively enhanced hydrophilicity and antifouling resistance, as suggested by the contact angle measurement and flux of bovine serum albumin solution tests, respectively. Accordingly, the PVC‐g‐P(PEGMA) graft copolymer was demonstrated as a successful additive for the hydrophilicity modification, and this study will likely open up new possibilities for the development of efficient amphiphilic PVC‐based copolymers for the excellent hydrophilicity modification of PVDF membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Hydrophilic modification of P(VDF-co-CTFE) porous membranes

This paper describes fabrication of a poly(vinylidene difluoride-co-chlorotrifluoroethylene) (P(VDF-co-CTFE)) porous membrane via non-solvent induced phase inversion and subsequent hydrophilic modification using high efficient surface initiated atom transfer radical polymerization (ATRP). The effect of viscosities of casting solutions on microstructures of the P(VDF-co-CTFE) membrane was investigated. The surface chemistry, thermal stability, morphological structure, and hydrophilicity of the modified membranes were evaluated by Fourier Transform Infrared Attenuated Total Reflection (FTIR-ATR), Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM), and contact angle measurements, respectively. The degree of grafting and the degree of swelling were measured to analyze the effect of polymerization time on the wettability. The mechanical strength of the membranes after modification was also investigated. The permeability and fouling resistance were evaluated according to pure water flux and protein solution filtration measurements. The results demonstrate that the hydrophobic P(VDF-co-CTFE) membrane can be feasibly modified by immobilization of hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) brushes via surface initiated ATRP.     

Development of a high-performance polysulfone hybrid ultrafiltration membrane using hydrophilic polymer-functionalized mesoporous SBA − 15 as filler

A novel polysulfone hybrid ultrafiltration membrane was developed by blending hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate] [P(PEGMA)] grafted mesoporous SBA-15 [SBA-g-P(PEGMA)] as filler. The hydrophilic SBA-g-P(PEGMA) fillers were synthesized via surface-initiated atom transfer radical polymerization. The effects of the SBA-g-P(PEGMA) fillers on the prepared hybrid membranes were systematically investigated. Compared with pristine SBA-15 fillers, SBA-g-P(PEGMA) fillers contributed to higher hydrophilicity and a more developed pore structure in the hybrid membranes. Specifically, SBA-15 grafted with a moderate P(PEGMA) molecular weight could better preserve the valid open-ended filler pore structure in the membrane matrix, thus facilitating membrane permeability. The pure water flux of the as-prepared polysulfone (PSF)/SBA-g-P(PEGMA) membrane was three times that of the PSF/SBA-15 membrane (271.7 L m⁻² h⁻¹ vs. 88.2 L m⁻² h⁻¹) with similar membrane selectivity. Moreover, the PSF/SBA-g-P(PEGMA) membranes showed improved antifouling property. This work paves the way for developing high-performance hybrid membranes by blending of hydrophilic polymer-functionalized mesoporous fillers in the future. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47353.     

Surface modification of contact lenses using adsorption of ethylene oxide branched copolymers

To examine methods for reducing the amount of adsorbed protein on the surface of contact lenses during use, cationic copolymers containing poly(ethylene oxide) units were synthesized and evaluated as surface modifiers. Poly(ethylene oxide) graft‐branched copolymers of composition 70 mol % dimethylaminoethyl methacrylate (DM) and 30 mol % methoxy polyethylene glycol methacrylate (Mp0G; p = 2, 4, 9; the average number of the ethylene oxide units) were obtained using nonionic monomers containing poly(ethylene oxide) units. The copolymers very efficiently prevented protein adsorption on a contact lens. Contact angle measurements showed that immersion in tear fluid made the lens surface hydrophobic because of adsorption of proteins with hydrophobic residues. The copolymer pretreatment made the lens surface hydrophilic, even after dipping in artificial tear fluid. These results suggest that adsorption of the poly(ethylene oxide) branched copolymer on the contact lens would make the lens surface hydrophilic and prevent protein adsorption. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biopolymer brushes grown on PDMS contact lenses by in situ atmospheric plasma-induced polymerization

It is critical for silicone based-contact lens development by improving surface characterization to prevent protein adsorption. In this paper, the silicone (polydimethylsiloxane, PDMS) contact lenses were modified by varied molecular weights of poly(ethylene glycol) methacrylate (PEGMA, Mw 360 and 500 Da) polymer brushes by in situ atmospheric plasma-induced surface copolymerization. After PDMS contact lenses were homogenously immersed in PEGMA monomer solutions, varied gases (oxygen, nitrogen, and argon) with the atmospheric plasma were employed in the process of polymerization. The characterizations of PEGMA polymer brushes modified on the PDMS contact lenses would be evaluated by atomic force microscopy, FT-IR spectroscopy, X-ray photoelectron spectroscopy, and contact angle test. The results show that the hydrophilicity of the PEGMA polymer brush-modified surface is obviously improved. The contact angle of PEGMA-modified surface decreases about 20°–40° by varied atmospheric plasma (O₂, N₂, and Ar gases), compared to the pristine lenses. Importantly, the hydrophilicity of the PEGMA polymer brush-modified surface could be retained beyond 2 weeks. PEGMA-modified PDMS contact lenses also display superior anti-protein (fibrinogen and human serum bovine) adsorption ability. Therefore, immobilization of PEGMA polymer brushes by in situ atmospheric plasma-induced polymerization would be a great and rapid method to enhance the hydrophilicity and anti-protein adsorption ability in the PDMS contact lenses.     

Amphiphilic poly(ether sulfone) membranes for oil/water separation: Effect of sequence structure of the modifier

Oil‐contaminated wastewater threatens our environment and health thus novel membrane materials with low or nonfouling properties are an immediate need for oily wastewater treatment in a cost‐effective and environmentally friendly manner. In this study, three types of amphiphilic random, gradient, and block copolymers with similar molecular weights and chemical compositions, based on poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctyl acrylate (TFOA), were synthesized by the reversible addition‐fragmentation chain transfer (RAFT) method. The amphiphilic Poly(ether sulfone) membranes were then fabricated by blending with these copolymers via a facile coupled process of nonsolvent induced phase separation and surface segregation. Accompanying the phase inversion process of polymer matrix, the hydrophilic and hydrophobic segments in the amphiphilic modifiers would migrate and immobilize onto the membrane surfaces. This surface segregation process leaded to a chemical heterogeneous membrane surface comprising both hydrophilic PEGMA and low surface energy PTFOA brushes, which was confirmed by X‐ray photoelectron spectroscopy (XPS) and surface wettability analyses. Oil‐in‐water emulsion filtration test of the membranes displayed a lower permeate flux decline and a higher flux recovery (as high as 99.8%), establishing their considerably elevated antifouling properties. Additionally, cyclic oil/water separation and long‐term underwater immersion tests demonstrated that the as‐prepared membranes modified by these amphiphilic additives possessed excellent antifouling stabilities. © 2016 American Institute of Chemical Engineers AIChE J, 63: 739–750, 2017     

Controlled grafting of polymer brushes on poly(vinylidene fluoride) films by surface‐initiated atom transfer radical polymerization

Controlled grafting of well‐defined polymer brushes on the poly(vinylidene fluoride) (PVDF) films was carried out by the surface‐initiated atom transfer radical polymerization (ATRP). Surface‐initiators were immobilized on the PVDF films by surface hydroxylation and esterification of the hydroxyl groups covalently linked to the surface with 2‐bromoisobutyrate bromide. Homopolymer brushes of methyl methacrylate (MMA) and poly(ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the α‐bromoester‐functionalized PVDF surface. The chemical composition of the graft‐functionalized PVDF surfaces was characterized by X‐ray photoelectron spectroscopy (XPS) and attenuated total reflectance (ATR)–FTIR spectroscopy. Kinetics study revealed a linear increase in the graft concentration of PMMA and PEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The “living” chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3704–3712, 2006     

Polysulfone-based amphiphilic copolymers: Effect of hydrophilic content on morphology and performance of ultrafiltration membranes

A series of polysulfone (PSf)-based amphiphilic graft copolymers were synthesized to investigate the effects of copolymer composition on membrane morphology and performance. PSf-based ultrafiltration membranes were prepared by phase inversion method using the blends of PSf and PSf-g-poly(ethylene glycol) methyl ether methacrylate (PEGMA) copolymers. Membranes were evaluated in terms of pure water permeability, flux recovery ratio (FRR), protein rejection, and contact angle. The morphology of the membranes was investigated by scanning electron microscopy. Contact angle of membranes was decreased from 85.7° to 51.6°, while the FRR was greatly increased from 55 to 95% upon increasing the PEGMA content of copolymers from 20 to 70 wt %. Results indicated that the ratio of hydrophilic/hydrophobic segments in amphiphilic structures is one the key parameters that control the phase inversion process by altering miscibility, viscosity, and wettability of casting solutions. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48306.     

Grafting of poly(ethylene glycol) monoacrylate onto polycarbonateurethane surfaces by ultraviolet radiation grafting polymerization to control hydrophilicity

In this study, we used a UV radiation grafting method to modify the surface of the biomaterial polycarbonateurethane (PCU). Hydrophilic poly(ethylene glycol) monoacrylate (PEGMA; number‐average molecular weight = 526) as a macromolecular monomer was grafted onto the PCU surface by UV photopolymerization. The Fourier transform infrared and X‐ray photoelectron spectroscopy results of the graft‐modified PCU confirmed poly[poly(ethylene glycol) monoacrylate] block grafting onto the surface. We investigated the effects of the reaction temperature, macromolecular monomer concentration, UV irradiation time, and photoinitiator concentration on the grafting density (GD) in detail. Furthermore, we investigated the effects of GD under various process conditions on the water uptake and water contact angle. The modified materials had a high water uptake and low water contact angle, which indicated that the hydrophilicity of the PCU surface was improved significantly by the introduction of the hydrophilic poly(ethylene glycol) blocks on the surface. The anticoagulant properties of the material might also have been improved. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chlorine-resistant and internal-concentration-polarization-mitigated polyamide membrane via tethering poly(ethylene glycol) methacrylate

To improve chlorine resistance and mitigate the internal concentration polarization (ICP), a membrane surface was tethered with poly(ethylene glycol) methacrylate (PEGMA). Characterization by attenuated total reflection–Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy analysis, and field emission scanning electron microscopy indicated the successful tethering of PEGMA onto the membrane. The antifouling and antichlorine characteristics were assessed in reverse osmosis (RO) and forward osmosis (FO) processes. The water flux increased obviously to 85.00 from 60.00 L m⁻² h⁻¹ (LMH) in the RO process; the chlorine stability of the modified membrane was improved. The greatly reduced structural parameters indicated that the ICP of the FO membrane was successfully alleviated; the water flux decreased greatly for the original membrane from 3.40 to 0.01 LMH, whereas it fell only slightly from 10.99 to 9.32 LMH for the modified membrane during synthetic sewage treatment. The ICP was greatly mitigated; the antichlorine performances and the antifouling characteristics drastically improved after grafting with PEGMA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47406.     

Novel dually responsive hydrogel with rapid deswelling rate

Hydrogels based on 2‐hydroxyethyl methacrylate (HEMA), methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) were prepared by free radical polymerization. The prepared hydrogels were characterized using Fourier transform infrared spectrometry. The states of water in the hydrogels were probed using differential scanning calorimetry and three types of water (free, freezing bound and non‐freezing bound) were detected, the contents of which were calculated. Compared with conventional poly(HEMA‐co‐MAA) hydrogels, the deswelling rate of the poly(HEMA‐co‐PEGMA‐co‐MAA) hydrogels is significantly improved, owing to the introduction of PEGMA. The deswelling process can be well described with a first‐order kinetics equation. Moreover, the swelling ratio of poly(HEMA‐co‐PEGMA‐co‐MAA) hydrogels exhibits a temperature dependence. Based on the analysis of the components of the hydrogels, a brushed core/shell structure is proposed for these, and confirmed by transmission electron microscopy observations. Copyright © 2006 Society of Chemical Industry     

Formation of poly(octadecyl acrylate) brushes on a silicon wafer surface

To introduce an ultrahydrophobic polymeric phase onto a silicon wafer, an initiator‐modified silicon wafer was prepared with 2‐bromopropionyl bromide and then surface‐initiated atom transfer radical polymerization of octadecyl acrylate was carried out from the initiator‐grafted silicon wafer using CuBr and N,N,N′,N″‐pentamethyldiethylenetriamine as catalyst precursors. The resultant poly(octadecyl acrylate) [poly(ODA)] brushes were characterized by ellipsometry, X‐ray photoelectron spectroscopy, grazing angle Fourier transform infrared spectroscopy, atomic force microscopy, gel permeation chromatography and water contact angle measurements. Wettability of the poly(ODA) brushes was found to depend on the surface coverage (Γ) and the root mean square roughness. The most hydrophobic surface (Γ = 25.35 mg m^?2 and root mean square roughness 11.9 nm) exhibited a water contact angle of 171.1 ± 0.2°. Copyright © 2011 Society of Chemical Industry     

Robust grafting of PEG-methacrylate brushes from polymeric coatings

A study is presented of the grafting of poly(ethylene glycol)methyl ether methacrylate (PEGMA) from polymeric macroinitiator films to form well-defined polymer brushes, using activators generated/regenerated by electron transfer (AGET/ARGET) atom transfer radical polymerization (ATRP). Polymer brush coatings can potentially be obtained on surfaces of virtually any shape and composition, because of the ease of conformal casting of the anchoring macroinitiator film. Polymer brush coatings are synthesized in a robust way, as ARGET and AGET ATRP require little to no deoxygenation and make use of stable catalysts. The monomer, catalyst, ligand and reducing agent concentrations, the amount and type of initiating moiety in the anchoring films, and the choice of solvents are optimized, resulting in control over the rate of reaction, and the molecular weight of poly(PEGMA). The best conditions are determined for the formation of a poly(PEGMA) brush with high grafting density, controlled thickness and “living” ends available for post-functionalization.     

Surface-initiated atom transfer radical polymerization of polyhedral oligomeric silsesquioxane (POSS) methacrylate from flat silicon wafer

A polyhedral oligomeric silsesquioxane (POSS) methacrylate monomer, i.e. 3-(3,5,7,9,11,13,15-heptacyclopentyl-pentacyclo [9.5.1.1.^3,91.^5,151^7,13]-octasiloxane-1-yl) propyl methacrylate (POSS-MA), was directly grafted from flat silicon wafers using surface-initiated atom transfer radical polymerization (ATRP). Two methods were used to improve the system livingness and control of polymer molecular weights. By ‘adding free initiator’ method, a linear relationship between the grafted poly(POSS-MA) layer thickness and monomer conversion was observed. By ‘adding deactivator’ method, the poly(POSS-MA) thickness increased linearly with reaction time. Poly(POSS-MA) layers up to 40 nm were obtained. The chemical compositions measured by X-ray photoelectron spectroscopy (XPS) agreed well with their theoretical values. Water contact angle measurements revealed that the grafted poly(POSS-MA) was extremely hydrophobic. The surface morphologies of the grafted polymer layers were studied by an atom force microscopy (AFM).     

Design of hemocompatible poly(DMAEMA‐co‐PEGMA) hydrogels for controlled release of insulin

This works aims at (i) studying the antiadhesive properties and the hemocompatibility of poly[2‐(dimethylamino)ethyl methacrylate]‐co‐poly[(ethylene glycol)methacrylate] [poly(DMAEMA‐co‐PEGMA)] copolymers and (ii) investigating the insulin delivery kinetics through hydrogels at physiological pH. A series of poly(DMAEMA‐co‐PEGMA) hydrogels have been synthesized, and their controlled composition was confirmed by X‐ray photoelectron spectroscopy. Then, antibiofouling properties of hydrogels—fibrinogen, erythrocytes, and thrombocytes adhesion—are correlated to their molecular compositions through their hydrophilic properties. As DMAEMA/PEGMA ratio of 70/30 (D70) offers the best compromise between pH sensitivity and hemocompatibility, it is selected for investigating the kinetic rate of insulin release at physiological pH, and the diffusion coefficient of insulin in gel is found to be 0.64 × 10^?7 cm² s^?1. Overall, this study unveils that poly(DMAEMA‐co‐PEGMA) copolymers are promising hemocompatible materials for drug delivery systems. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42365.     

Covalently tethered comb‐like polymer brushes on hydrogen‐terminated Si (100) surface via consecutive aqueous atom transfer radical polymerization of methacrylates

The hydrogen‐terminated Si (100) (Si? H surface) was functionalized by coupling with 4‐vinylbenzyl chloride (VBC) to form a Si? VBC surface, which serves as macroinitiators for the surface‐initiated aqueous atom transfer radical polymerization (ATRP) of 2‐hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol)methacrylate (PEGMA) to prepare Si? VBC? g? PHEMA and Si? VBC? g? PPEGMA substrates, respectively. The ellipsometric results revealed that the surface‐initiated ATRP of both PHEMA and PPEGMA brushes proceeded in a controlled fashion. By adjusting the monomer concentration, an eccentric polymer thickness dependence on the initial monomer concentration [M]₀ was observed for both HEMA and PEGMA, i.e., in the dilute regime, the thickness of the polymer film increases with the increase in [M]₀; however, beyond critical [M]₀, the thickness deceases gradually with the further increase. Such an eccentricity was tentatively correlated to the counteractive combination of the increase in [M]₀ and decrease in the apparent polymerization rate constant. Both Si? VBC? g? PHEMA and Si? VBC? g? PPEGMA substrates were esterified for the subsequent surface‐initiated ATRP, resulting in corresponding comb‐like brushes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2590–2599, 2006     

Evaporation of Ethanol-Water Mixture Drop on Horizontal Substrate

This study investigates the evaporation of sessile drop comprising ethanol and water mixture on horizontal poly methyl methacrylate surface. The contact angle (θ) and contact radius (R) of ethanol-water mixture drop are recorded with time, considering the impacts of presence of ethanol. With excess ethanol, the drop evaporation is principally controlled by a phase in which both the contact angle and contact radius are falling. A diffusional model assuming linear relation between contact radius and time is proposed as θ = eR ^?3 + cR ^?1, where e and c denote fitting coefficients. This model correlates with the experimental data.     

Superabsorbent polymeric materials. XI. Effect of nonionic monomers on the swelling behavior of crosslinked poly(sodium acrylate‐co‐nonionic monomers) in aqueous salt solutions

A series of xerogels based on sodium acrylate, nonionic monomers such as 2‐hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEGMA), and N,N′‐methylene bisacrylamide were prepared by inverse suspension polymerization. The results indicate that the water absorbencies for these two gel series were effectively improved by the addition of a small amount of nonionic monomer (HEMA or PEGMA). The initial absorption rates in deionized water were faster for the PEGMA gels than for the HEMA gels. Scanning electron microscopy showed that the spherical particle size was smaller for the PEGMA gels than for the HEMA gels. In addition, the water absorbency of the gels in various salt solutions decreased with increasing ionic strength, especially for the multivalent salt solutions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3666–3674, 2004