A FACILE APPROAC0H FOR THE SURFACE MODIFICATION OF POLY(VINYLIDENE FLUORIDE)MEMBRANE VIA SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

A novel approach for the surface modification of poly(vinylidene fluoride)(PVDF)membrane was successfully realized through alkaline treatment,UV-induced bromine addition,and followed by surface-initiated atom transfer radical polymerization(ATRP)of methyl methacrylate(MMA).Chemical changes on the PVDF membrane before and after modification were analyzed with attenuated total reflectance Fourier transform infrared spectroscopy(AIR/Fr-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revealed that the chain growth of poly(methyl methacrylate)(PMMA)from the PVDF surface is consistent with a"controlled"process.     

表面引发的原子转移自由基聚合法在聚偏二氟乙烯表面制备可控的聚甲基丙烯酸甲酯刷

采用表面引发的原子转移自由基聚合法(ATRP)在聚偏二氟乙烯(PVDF)表面制备结构可控的聚甲基丙烯酸甲酯刷。通过碱处理和紫外光照溴代的方法,将ATRP引入到PVDF表面; 然后采用ATRP法将甲基丙烯酸甲酯接枝到溴代的PVDF表面。采用傅里叶变换红外光谱和X-射线光电子能谱对改性前后PVDF表面的结构进行了表征。结果表明甲基丙烯酸甲酯成功地接枝到了PVDF表面。     

白蛋白原位复合生物医用功能材料的研究(Ⅰ)──材料的合成和表面结构研究

采用大分子单体技术合成了以聚甲基丙烯酸甲酯为主链,聚氧乙烯链为侧链,末端为白蛋白诱导吸附基团的十八烷基功能聚合物聚甲基丙烯酸甲酯接枝十八烷基聚氧乙烯.采用变角X光电子能谱和表面接触角研究了该功能聚合物在空气和水界面的性质.结果表明,在聚合物-空气界面,十八烷基聚氧乙烯(SPEO)的表面含量随表面层厚度的降低而升高,并在表面发生高度富集.在聚合物-水界面,聚合物表面重组行为较弱,形成了高SPEO含量的疏水表面,该SPEO尾形结构表面预期可发挥聚氧乙烯和十八烷基的协同作用,形成白蛋白原位复合的生物医用功能材料.     

PVDF/PMMA brushes membrane for lithium‐ion rechargeable batteries prepared via preirradiation grafting technique

Poly(methyl methacrylate) (PMMA) was anchored to multiporous poly(vinylidine fluoride) (PVDF) surface via electron beam preirradiation grafting technique to prepare PVDF/PMMA brushes. The conformation of the PVDF/PMMA brushes was verified through Attenuated total reflection‐Fourier transform infra red spectroscopy (ATR‐FTIR), energy dispersive X‐ray spectroscopy (EDX), and scanning electron microscopy (SEM). Thermal stability of PVDF/PMMA brushes was characterized by thermo gravimetric analysis (TGA). The degradation of PVDF/PMMA brushes showed a two‐step pattern. PVDF/PMMA brushes membrane could be used as polymer electrolyte in lithium‐ion rechargeable batteries after it was activated by uptaking 1 M LiPF₆/EC‐DMC (ethylene carbonate/dimethyl carbonate; EC:DMC = 1:1 by volume) electrolyte solution. The activated membrane showed high ionic conductivity, 6.1 × 10^?3 S cm^?1 at room temperature, and a good electrochemical stability up to 5.0 V. The excellent performances of multiporous PVDF‐g‐PMMA membranes suggest that they are suitable for application in high‐performance lithium‐ion batteries. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 751–758, 2008     

Controlled grafting from poly(vinylidene fluoride) films by surface‐initiated reversible addition–fragmentation chain transfer polymerization

A reversible addition–fragmentation chain transfer (RAFT) polymerization technique was applied to graft polymerize brushes of poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) monomethacrylate) (PPEGMA) from poly(vinylidene fluoride) (PVDF) surfaces. PVDF surfaces were exposed to aqueous LiOH, followed by successive reductions with NaBH₄ and DIBAL‐H to obtain hydroxyl functionality. Azo‐functionalities, as surface initiators for grafting, were immobilized on the PVDF surfaces by esterification of 4,4′‐azobis(4‐cyanopentanoic acid) and the surface hydroxyl groups. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance‐FTIR spectroscopy, and atomic force microscopy. Kinetics studies revealed a linear increase in the graft concentration of PMMA and PPEGMA 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 Polym Sci Part A: Polym Chem 44: 3071–3082, 2006     

Atom transfer radical polymerization directly from poly(vinylidene fluoride): Surface and antifouling properties

The direct preparation of grafting polymer brushes from commercial poly (vinylidene fluoride) (PVDF) films with surface‐initiated atom transfer radical polymerization (ATRP) is demonstrated. The direct initiation of the secondary fluorinated site of PVDF facilitated grafting of the hydrophilic monomers from the PVDF surface. Homopolymer brushes of 2‐(N,N‐dimethylamino)ethyl methacrylate (DMAEMA) and poly (ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the PVDF surface. The chemical composition and surface topography of the graft‐functionalized PVDF surfaces were characterized by X‐ray photoelectron spectroscopy, attenuated total reflectance/Fourier transform infrared spectroscopy, and atomic force microscopy. A kinetic study revealed a linear increase in the graft concentration of poly[2‐(N,N‐dimethylamino)ethyl methacrylate] (PDMAEMA) and poly[poly(ethylene glycol) monomethacrylate] (PPEGMA) 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 macroinitiators for the synthesis of diblock copolymer brushes. The water contact angles on PVDF films were reduced by the surface grafting of DMAEMA and PEGMA. Protein adsorption experiments revealed a substantial antifouling property of PPEGMA‐grafted PVDF films and PDMAEMA‐grafted PVDF films in comparison with the pristine PVDF surface. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3434–3443, 2006     

Hydrophilic modification of poly(vinylidene fluoride) (PVDF) by in situ polymerization of methyl methacrylate (MMA) monomer

The hydrophilicity of poly(vinylidene fluoride) (PVDF) was first improved by in situ polymerization of polar monomer in PVDF solution. Methyl methacrylate was adopted as the reaction monomer, and the polymerization occurred in a solution of PVDF in N,N-dimethylformamide. PVDF/poly(methyl methacrylate) (PMMA) blend was obtained after in situ polymerization. The relative hydrophilicity of the in situ blend was characterized by contact angle measurement. At the same time, the hydrophilicity of the PVDF/PMMA blends prepared by solution blending was compared with that of the in situ blend. The contact angle measurements indicated that in situ polymerization has a stronger modifying effect on the hydrophilicity of PVDF than solution blending.     

A novel approach to modify poly(vinylidene fluoride) via iron‐mediated atom transfer radical polymerization using activators generated by electron transfer

Iron‐mediated atom transfer radical polymerization using activators generated by electron transfer directly from the secondary fluorine atoms on the poly(vinylidene fluoride) (PVDF) backbone, using methyl methacrylate (MMA) and poly (ethylene glycol) methyl ether methacrylate (PEGMA) as the monomers, FeCl₃·6H₂O as the catalyst, PPh₃ as the ligand, and vitamin C as the reducing agent, was demonstrated in the presence of limited amounts of air. The successful syntheses of the corresponding graft copolymers PVDF‐g‐PMMA and PVDF‐g‐PPEGMA were characterized by nuclear magnetic resonance, Fourier transform infrared and X‐ray photoelectron spectroscopy, respectively. The graft copolymers PVDF‐g‐PPEGMA can be readily cast into porous hydrophilic microfiltration membranes by phase inversion in an aqueous medium. The morphologies were characterized by scanning electron microscopy. The surface and bulk hydrophilicity were evaluated on the basis of static water contact angle and the steady adsorption of bovine serum albumin. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Multi‐functional poly(vinylidene fluoride) graft copolymers

Poly(vinylidene fluoride) (PVDF) is known for its biocompatibility, piezo and pyro‐electricity, and membrane forming capability. In order to tune its properties, modification through grafting from approach by atom transfer radical polymerization (ATRP) is preferred. Hydrophilic polymers like poly(ethylene glycol) methacrylate, poly(methacrylic acid), poly(dimethylaminoethyl methacrylate) (PDMAEMA), and so forth have been anchored from PVDF backbone in order to make permeation of water molecules through the PVDF based membranes. The successful solution grafting of PDMAEMA chains from PVDF backbone by ATRP resulted appreciable graft conversion and hence its bulk properties showed a significant change. This water soluble graft copolymer shows incredible mechanical and adhesive properties. PVDF‐g‐poly(n‐butyl methacrylate) generates honey‐comb porous film using “breath figure” technique. Recently, they have used further improvement of grafting where model ATRP initiators are anchored using atom transfer radical coupling and used them as macroinitiators for grafting. This approach simplified the grafting reactions even more and enabled successful grafting of a large number of monomers under relatively less drastic conditions with appreciable conversion compared with the previous conditions. This technique has resulted interesting solution properties, ion and electron conducting PVDF, antifouling membrane, super glue and super tough materials, capable of generating metal nanoparticles tunable with pH and temperature. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2569–2584     

Multilayered poly(vinylidene fluoride) composite membranes with improved interfacial compatibility: correlating pervaporation performance with free volume properties

A spin-coating process integrated with an ozone-induced graft polymerization technique was applied in this study. The purpose was to improve the poor interfacial compatibility between a selective layer of poly(2-hydroxyethyl methacrylate) (PHEMA) and the surface of a poly(vinylidene fluoride) (PVDF) substrate. The composite membranes thus fabricated were tested for their pervaporation performance in dehydrating an ethyl acetate/water mixture. Furthermore, the composite membranes were characterized by field emission scanning electron microscopy (FE-SEM) for morphological change observation and by Fourier transform infrared spectroscopy equipped with attenuated total reflectance (ATR-FTIR) for surface chemical composition analysis. Effects of grafting density and spin-coating speed on pervaporation performance were examined. The composite membrane pervaporation performance was elucidated by means of free volume and depth profile data obtained with the use of a variable monoenergy slow positron beam (VMSPB). Results indicated that a smaller free volume was correlated with a higher pervaporation performance of a composite membrane consisting of a selective layer of spin-coated PHEMA on a PHEMA-grafted PVDF substrate (S-PHEMA/PHEMA-g-PVDF). The composite membrane depth profile illustrated that an S-PHEMA layer spin-coated at a higher revolutions per minute (rpm) was thinner and denser than that at a lower rpm.     

Self‐emulsification and surface modification effect of fluorinated amphiphilic acrylate graft copolymers

We report on self‐emulsification and surface modification effect of novel fluorinated amphiphilic graft copolymers prepared with perfluoroalkyl acrylate and 2‐dimethylaminoethyl methacrylate using simple macromonomer technique and radical copolymerization. The interfacial properties of amphiphilic graft copolymers were characterized with light scattering, contact angle measurement, and X‐ray photoelectron spectroscopy. The preparation of fluorinated amphiphilic graft copolymer was verified using nuclear magnetic resonance and Fourier transform infrared spectroscopy. It was observed that the fluorinated amphiphilic graft copolymer has both strong hydrophobic and hydrophilic properties and shows self‐emulsification ability without addition of external surfactants. The graft copolymer shows very low surface energy even though the copolymer has low content of hydrophobic segment and better performance than random copolymer for low‐energy surface modification. The addition of small amount of the graft copolymer (0.1 wt %) into the base poly(methyl methacrylate) was sufficient to lower the surface energy less than that of poly(tetrafluoroethylene). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Improving hydrophilicity and protein antifouling of electrospun poly(vinylidenefluoride-hexafluoropropylene) nanofiber membranes

<正>Poly(vinylidenefluoride-hexafluoropropylene)(PVDF-HFP) nanofiber membranes with improved hydrophilicity and protein fouling resistance via surface graft copolymerization of hydrophilic monomers were prepared.The surface modification involves atmospheric pressure glow discharge plasma(APGDP) pretreatment followed by graft copolymerization of poly(ethylene glycol) methyl ether methacrylate(PEGMA).The success of the graft modification with PEGMA on the PVDF-HFP fibrous membrane is ascertained by X-ray photoelectron spectroscopy(XPS) and attenuated total reflectance Fourier transform infrared measurements(ATR-FTIR).The hydrophilic property of the nanofiber membranes is assessed by water contact angle measurements.The results show that the PEGMA grafted PVDF-HFP nanofiber membrane has a water contact angle of 0°compared with the pristine value of 132°.The protein adsorption was effectively reduced after PEGMA grafting on the PVDF-HFP nanofiber membrane surface.The PEGMA polymer grafting density on the PVDF-HFP membrane surface is measured by the gravimetric method,and the filtration performance is characterized by the measurement of water flux.The results indicate that the water flux of the grafted PVDF-HFP fibrous membrane increases significantly with the increase of the PEGMA grafting density.     

超亲水聚偏氟乙烯中空纤维膜的制备及性能

采用超声辅助接枝聚合技术, 将甲基丙烯酸缩水甘油酯(GMA)接枝到聚偏氟乙烯(PVDF)膜表面, 制备PVDF-g-GMA膜; 再利用氨基诱导环氧基团发生开环反应, 将苏氨酸(Thr)接枝到PVDF-g-GMA膜表面, 制备了具有两性离子结构表面的PVDF-g-GMA-Thr膜. 通过衰减全反射傅里叶变换红外光谱(ATR-FTIR)、 X射线光电子能谱(XPS)、 接触角测试仪、 场发射扫描电子显微镜(FESEM)和牛血清白蛋白(BSA)过滤实验等系统研究了改性前后PVDF膜表面的化学组成、 润湿性能、 表面形貌和抗污染性能. 研究结果表明, 随着PVDF-g-GMA接枝Thr反应时间的增加, PVDF-g-GMA-Thr膜的亲水性能明显提高, 接触角从90°降为0°, 呈现出超亲水性能. 同时PVDF-g-GMA-Thr膜的水通量明显提高, 当Thr诱导开环反应时间为12 h时, PVDF-g-GMA-Thr膜的水通量高达686 L/(m ²·h), 与PVDF原膜相比, 水通量提高了204.5%. 在BSA的过滤测试中, 与PVDF膜相比, PVDF-g-GMA-Thr膜呈现出良好的截留性能和抗污染性能, BSA截留率从42%提高到84%,水通量恢复率从53%提高到87%, 不可逆污染率从47%降到12%, 表明通过接枝Thr构筑两性离子结构表面可以有效减小膜污染.     

PMMA/PVDF共混对PVDF的β相构型影响的研究

采用溶液法制备了不同含量的聚甲基丙烯酸甲酯/聚偏二氟乙烯(PMMA/PVDF)共混薄膜,利用傅立叶变换红外光谱(FTIR)、X射线衍射谱(XRD)、和差热分析法(DSC)对共混薄膜的结晶行为进行了分析。结果表明,共混物中PMMA的含量对PVDF的β相构型有明显影响:PMMA/PVDF=30/70共混物中β相含量最高。为提高PVDF薄膜的铁电性能提供了新的研究方法。     

HYDROPHILIC MODIFICATION OF PPESK POROUS MEMBRANES VIA AQUEOUS SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

Hydrophilic surface modification of poly(phthalazinone ether sulfone ketone)(PPESK) porous membranes was achieved via surface-initiated atom transfer radical polymerization(ATRP) in aqueous medium.Prior to ATRP.chloromethyl groups were introduced onto PPESK main chains by chloromethylation.Chloromethvlated PPESK(CMPPESK) was fabricated into porous membrane through phase inversion technique.Hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate)(P(PEGMA)) brushes were grafted from CMPPESK membra...     

Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations

Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy.     

Deposition of PEG onto PMMA microchannel surface to minimize nonspecific adsorption

A protein-resistant surface has been constructed on the poly(methyl methacrylate) (PMMA) microfluidic chips based on a one-step modification. The copolymer of butyl methacrylate (BMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) is synthesized to introduce a dense PEG molecular brush-like coating on the PMMA microchannel surfaces via the anchoring effect of the hydrophobic BMA units. The PEGMA segments could produce hydrophilic domains formed on the interface so as to achieve stable electroosmotic flow, and less nonspecific adsorption toward biomolecules. The modification procedure and the properties of the poly(BMA-co-PEGMA)-coated surface have been characterized by FT-IR spectroscopy, confocal fluorescence microscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The water contact angle and electroosmotic flow of PEG-modified PMMA microchip are measured to be 36 degrees and 5.4 x 10(-4) cm(2) V(-1) s(-1), while those of 73 degrees and 1.9 x 10(-4) cm(2) V(-1) s(-1) for native one, respectively. The PEG-modified microchip has been applied for the electrophoresis separation of proteins, corresponding to the theoretical efficiencies about 16 300 and 412 300 plates m(-1). In the interest of achieving efficient separation while minimizing biofoulings from the serum and plasma, the fabrication of PEG-coated microfluidic chips would provide a biocompatible platform for complex biological analysis.     

Investigation of the detection limit for the determination,by pyrolysis-capillary GC,of the thickness of ultra thin PMMA layers coated on to PET film

The determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)-to-poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.     

High ionic conductive PVDF-based fibrous electrolytes

The high ionic conductive polymer electrolytes were prepared based on poly(vinylidenefluoride) (PVDF) fibers modified via preirradiation grafting poly(methyl methacrylate) (PMMA). In these polymer electrolytes, the PVDF fibers served as the supporting phase providing dimensional stability, and PMMA acted as the gel phase helping for the trapping liquid electrolyte and substituting the nonconductive PVDF phase to provide contact with electrodes well thus increasing conductive area. The modified PVDF fibrous membranes were used as a polymer electrolyte in lithium ion battery after they were activated by uptaking 1 M LiPF₆/ethylene carbonate–dimethyl carbonate (1:1 vol) liquid electrolyte, which showed a much higher room-temperature ionic conductivity than the pristine PVDF fibrous membrane. The LiCoO₂-mesocarbon microbead coin cells containing the dual-phase fibrous membrane (degree of graft, 111.8%) demonstrated excellent rate performance, and the cell still retained about 86% of discharge capacity at 4C rate, as compared to that at 0.1C rate. The prototype cell showed good cycle performance.     

Grafting acrylic polymers from flat nickel and copper surfaces by surface-initiated atom transfer radical polymerization

Acrylic polymers, including poly(methyl methacrylate), poly(2,2,2-trifluoroethyl methacrylate), poly( N,N'-dimethyaminoethyl methacrylate), and poly(2-hydroxyethyl methacrylate) were grafted from flat nickel and copper surfaces through surface-initiated atom transfer radical polymerization (ATRP). For the nickel system, there was a linear relationship between polymer layer thickness and monomer conversion or molecular weight of "free" polymers. The thickness of the polymer brush films was greater than 80 nm after 6 h of reaction time. The grafting density was estimated to be 0.40 chains/nm2. The "living" chain ends of grafted polymers were still active and initiated the growth of a second block of polymer. Block copolymer brushes with different block sequences were successfully prepared. The experimental surface chemical compositions as measured by X-ray photoelectron spectroscopy agreed very well with their theoretical values. Water contact angle measurements further confirmed the successful grafting of polymers from nickel and copper surfaces. The surface morphologies of all samples were studied by atomic force microscopy. This study provided a novel approach to prepare stable functional polymer coatings on reactive metal surfaces.