Comparison of two approaches to grafting hydrophilic polymer chains onto polysulfone films

To reduce the surface protein adsorption of polysulfone (PSf) film, we improved the hydrophilicity of this film by photochemical grafting of methoxypoly (ethylene glycol) (MPEG) derivatives on its surface. Grafting was achieved with both the simultaneous method and the sequential method. Surface analysis of the grafted film by X‐ray photoelectron spectroscopy (XPS) revealed that the PEG chains had successfully grafted onto the surface of the film. The grafting efficiencies by simultaneous and sequential methods were 20.8% and 10.2%, respectively. With an atomic force microscope (AFM), the surface topography of PEG‐grafted films by these two methods was compared. Static water contact angle measurement indicated that the surface hydrophilicity of the film had been improved. Protein adsorption measurement showed that the surface protein adsorption of the modified film was significantly reduced compared with that of the unmodified PSf film. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3818–3826, 2007     

Graft polymerization of propylene sulfide on crosslinked polystyrene

Sulfur containing graft polymers that may be of interest as polymeric transfer agents were synthesized. Graft polymerization of propylene sulfide on crosslinked polystyrene beads was investigated; both crosslinked polystyrene and its chloromethylated derivative were grafted. Crosslinked polystyrene was metallated by BuLi–TMEDA and was used to initiate anionic graft polymerization of propylene sulfide. Graft polymers of high polypropylene sulfide content corresponding to 10 mmol s/g were obtained. The grafted polypropylene sulfide was evenly distributed across the bead cross section. No change in bead surface characteristics was observed. Grafting on chloromethylated polystyrene beads was achieved by reaction between the chloromethylene groups with sulfide groups of performed polypropylene sulfide, and with terminal sodium thiolate groups of living polypropylene sulfide.     

Modification of adhesive properties of a polyethylene film by photografting

Graft polymerization of acrylic acid from monomer solutions in water or in bulk onto low‐density polyethylene film substrate was carried out by the method of continuous process under UV radiation. Effects of the nature of photoinitiator on acrylic acid grafting was first studied. One PI₂ and two PI₁ photoinitiators were used. Benzophenone was then retained for the following study. The influence of photoinitiator and monomer concentration was investigated by determining polymerization kinetics and grafted polymer amount. A study of surface wetting and morphological structure was then carried out on a bulk system and as a function of the photoinitiator concentration. Finally, such surface modification was studied with respect to its effect on the adhesion of an acrylic stick on its surface. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2803–2811, 2004     

Photografting of acrylamide on ethylene–vinyl alcohol copolymer film

Photografting (λ > 300nm) of acrylamide on ethylene-vinyl alcohol copolymer film (vinyl alcohol unit = 56 mol%, film thickness = 20μm) was investigated at 60°C in water medium, where photoinitiators were coated on the film earlier. The percent grafting decreased in the order of xanthone ≈ benzophenone > anthraquinone > benzoyl peroxide. The graft efficiencies in each sensitized system were less than 30%, showing a predominant formation of homopolymer. Grafting of acrylamide on the film was also initiated in systems with and without photoirradiation when ceric salt was used as an initiator. Based on electron probe microanalysis of the grafted films, the grafted chains of the sample prepared by photografting were distributed inside the film, while those of the sample prepared by ceric salt-initiated grafting without photoirradiation were located mainly on the film surface. The grafted films prepared by the former system exhibited a higher moisture permeability than those prepared by the latter system.     

Construction of a choline biosensor through enzyme immobilization on a poly(2‐hydroxyethyl methacrylate)‐grafted Teflon film

An amperometric choline biosensor was constructed by immobilizing choline oxidase (ChO) on poly(2‐hydroxyethyl methacrylate) (PHEMA)‐grafted Teflon (polytetrafluoroethylene, PTFE) film. Grafting was achieved by γ irradiation. PHEMA‐grafted Teflon films were activated with epichlorohydrin or glutaraldehyde to achieve covalent immobilization of enzyme onto the film. To decrease the diffusional barrier caused by the enzyme‐immobilized film, the film was stretched directly on the electrode. The PHEMA‐grafted Teflon film, therefore, had to have appropriate mechanical properties. Glucose oxidase (GOD) was used in the determination of optimum immobilization conditions, then these were applied to ChO. With GOD, the effect of activation type and film position in electrode on enzyme activity was studied and the highest catalytic activity was obtained when the enzyme was immobilized using glutaraldehyde and the film was stretched over the electrode surface. Further studies revealed that the films activated with glutaraldehyde, immobilized in 2 mg/mL ChO concentration, and stretched directly on the electrode were suitable (specific activity, 0.427 ± 0.068 U mg^?1) for use in the choline biosensor. The linear working range of this biosensor was found to be 52–348 μM, with a 40 ± 5 μM minimum detection limit. The response of the sensor, however, decreased linearly upon repeated use. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Grafting Polymerization of Acrylonitrile onto LDPE Film: Study on Grafting Chain Length and Density with UV-vis Spectroscopy

Summary Grafting polymerization of acrylonitrile onto low density polyethylene film was studied further following the earlier work [1]. A novel and effective method was developed to directly determine the number of end-groups, i.e. phenyls at the end of grafted chains with UV-vis spectroscopy; according to the number of phenyl end-groups and the weight of grafted polymers, grafting chain length and density were estimated; investigations indicated both of these two parameters could be practically controlled.     

Surface modification of styrene-divinylbenzene copolymers by polyacrylamide grafting via gamma irradiation

Polyacrylamide chains were grafted onto styrene-divinylbenzene (S-DVB) copolymer beads using gamma radiation from a ⁶⁰Co source by applying the simultaneous method. S-DVB macroporous copolymer was synthesized by aqueous suspension polymerization and characterized by determining apparent density, surface area, pore volume distribution and water uptake. Optical and electron microscopies were used in order to observe the copolymer morphology. The effect of parameters such as monomers concentration, irradiation dose and presence of inhibitor (Mohr’s salt) on grafting reaction was studied. The grafting reaction was evaluated with the aid of elemental analysis, FTIR, HR-MAS NMR spectrometry, thermogravimetry (TG) and electron microscopy. Grafting yield (evaluated by nitrogen content) increased with acrylamide concentration and irradiation dose increasing. However, above determined values of those parameters it is observed a tendency of decreasing on the grafting yield. The presence of Mohr’s salt inhibited the production of homopolymer as well as the progress of the grafting reaction.     

Tailoring bulk and surface grafting of poly(acrylic acid) in electron-irradiated PVDF

Endowing conventional hydrophobic poly(vinylidene fluoride) (PVDF) films with hydrophilic properties was conducted using electron beam irradiation. Grafting of acrylic acid (AA) in/onto pre-irradiated PVDF films was investigated. Reaction parameters, monomer concentration and inhibitor concentration were examined. Radiation grafted films (PVDF-g-PAA) were synthesized with various grafting yields ranging from 12 to 130 wt % in presence of Mohr's salt (25 wt %). Below 80 wt % of monomer concentration, the degree of swelling was found to increase with the grafting yield. The PAA was arranged randomly in all PVDF matrix (grafting through). Above 80 wt % of monomer concentration, the PAA was grafted only onto the surface of PVDF films leading to a highly dense layer of PAA. Grafting through or surface grafting processes were achieved by varying the water fraction in the initial monomer solution. Water molecule acts not only as a carrier for the monomer but also as a plasticizer expanding the film in the three dimensions. Evidences of grafting through and surface grafting were produced using FTIR in ATR mode, SEM coupled to X-ray detection and XPS. An accurate quantification of AA units was possible up to the micromole via a Cu²⁺–EDTA complex analyzed by UV–vis spectroscopy.     

单股流布水改性碳钢表面的润湿特性

湿式静电除尘技术收尘极表面的易腐蚀和水膜均布问题是影响该技术连续可靠运行的重要因素。针对这两个问题,对碳素钢冷轧成型板进行了抗腐蚀保护层和在保护层基础上黏附不同附加亲水层的改性。使用称重法和平面成像法进行了单股流布水不同Reynolds数下不同改性表面持液量、表面流量、成膜率、水膜平均厚度等润湿特性的研究。结果表明:抗腐蚀保护层降低基材的润湿特性,附加亲水层中台丽碳纤维布的持液量较基材碳钢表面增加1.0～2.2倍,细沙粒成膜率比基材碳钢增加50%～60%,水膜厚度均在0.3～0.7 mm之间(最大达1.4 mm);玻璃纤维布黏附在环氧树脂表面的疏松程度直接影响表面的润湿特性,涂刷第3层环氧树脂后自然晾晒12 h,120℃加热1 h后敷设玻纤布,自然冷却至固化得到的表面润湿特性最佳,其持液量可达0.014～0.021 g·cm^-2,临界饱和时间 < 3 min,实现完全润湿,成膜率较基材增加34～40倍;改性材料表面布水参数:喷水孔间距≥10 cm、Reynolds数超过2000,此时表面液膜为波动层流,可获得理想冲刷效果。     

Synthesis and characterization of magnetic beads containing aminated fibrous surfaces for removal of Reactive Green 19 dye: kinetics and thermodynamic parameters

BACKGROUND: Poly(HEMA‐co‐MMA) beads were prepared from 2‐hydroxyethyl‐methacrylate (HEMA) and methylmethacrylate (MMA) in the presence of FeCl₃. Thermal co‐precipitation of Fe(III) ions containing beads with Fe(II) ions was carried out under alkaline conditions. The magnetic beads were grafted with poly(glycidylmethacrylate; p(GMA)), and the epoxy groups of the grafted p(GMA) brushes were converted into amino groups by reaction with ammonia. RESULTS: The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), Mössbauer spectroscopy and scanning electron microscopy (SEM). The maximum adsorption of Reactive Green‐19 (RG‐19) dye on the p(GMA) grafted and amine modified magnetic beads was around pH 3.0. The adsorption capacity of magnetic beads was 84.6 mg dye g^?1. The effects of adsorbent dosage, ionic strength and temperature have also been reported. Batch kinetic sorption experiments showed that a pseudo‐second‐order rate kinetic model was applicable. CONCLUSION: The p(GMA) grafted and amine modified magnetic beads (adsorbent) were expected to have the advantage of mobility of the grafted chains in the removal of acidic dyes from aqueous solutions. The magnetic beads have potential as an adsorbent for removal of pollutants under various experimental conditions without significant reduction in their initial adsorption capacity. Copyright © 2011 Society of Chemical Industry     

Graft polymerization of acrylic acid onto polyethylene film by preirradiation method. I. Effects of preirradiation dose,monomer concentration,reaction temperature,and film thickness

Low-and high-density polyethylenes were irradiated by electron beams with dose of 2–50 Mrad and then immersed in aqueous solution of acrylic acid (monomer concentration from 30 to 100 wt %) for 10 min?5 h at a temperature of 25–40°C. The degree of grafting increases with time and levels off. High density polyethylene shows lower grafting rate and higher final % grafting in compared with low-density polyethylene. Both grafting rate and final % grafting increase with total dose of preirradiation, but show some saturation at high doses. The highest grafting rate was observed at 60 wt % of monomer concentration where the grafted polyethylene swells to the largest extent in the monomer mixture. Apparent activation energies for the grafting are 19.6 and 27.3 kcal/mol for low- and high-density polyethylenes, respectively, reflecting the proces of monomer diffusion in the film. Grafting rate decreases with increasing film thickness. Graft polymerization starts on the surface of the film and proceeds to the inner part with monomer diffusion through the grafted layer.     

Preparation and characterization of teflon–FEP films grafted with acrylic acid by radiochemical method

In an attempt to prepare permselective membrane, grafting of acrylic acid (AAc) onto Teflon–fluorinated ethylene-propylene (FEP) film was studied in aqueous medium by the preirradiation method in air. Grafting was carried out by heating a mixture of AAc, water, and preirradiated Teflon–FEP film in air at 93°C for definite time periods. Percentage ofgrafting was determined as a function of total dose, monomer concentration, reaction time, and amount of water. Maximum percentage of grafting (60.17%) was obtained at a total dose of 4.8 Mrad using 0.07M [AAc]. Evidence of grafting was obtained from the physical appearance and swelling behavior of the grafted film in polar solvents. Infrared spectroscopic and thermal analysis of the grafted film provided additional evidence for grafting. A plausible mechanism for grafting of AAc onto preirradiated Teflon–FEP film in air has been proposed. © 1995 John Wiley & Sons, Inc.     

Correlation between surface energy and uptake behavior of radiation-grafted methacrylic acid-g-LDPE

An efficient and low-cost effluent adsorbent has been developed by grafting an ionizable monomer onto polyolefin surface and its efficacy was tested for dyes and metal ion uptake from aqueous medium. The grafted matrix was synthesized by optimizing various experimental parameters such as irradiation dose, dose rate, monomer concentration, inhibitor concentration, surfactant concentration, and backbone thickness. Grafting yield decreased with dose rate and thickness and increased with the concentration of methacrylic acid and inhibitor. Grafting kinetics studies indicated that grafting rate is comparatively much affected by dose rate that monomer concentration. Surface energy of the grafted surface was accessed from dynamic contact angle measurements. Uptake study of Basic Red 29, Methylene Blue showed high correlation with grafting yield and polar component of the surface energy; however, metal ion uptake was exceptionally high at ~25 grafting (%), highlighting anomalous behavior of MAA-g-LDPE with respect to surface energy and total ion uptake capacity.     

Modification of industrial polypropylene film by grafting of poly(acrylic acid)

Grafting of poly(acrylic acid) onto commercial polypropylene films following irradiation by γ-rays was carried out in order to improve their surface properties. The amount of grafting with the irradiation dose was found not to follow the expected linear dependence as it is normally observed for polypropylene films prepared in laboratory amounts. We therefore analyzed the influence of the industrial manufacture process in terms of orientation of the film and addition of antioxidants by determining the peroxide surface density and the extent of grafting therefrom. The unoriented polypropylene film presented the highest peroxide concentration and was thus the most adapated material for successful grafting. Whereas phenol antioxidants limit the peroxide formation and thus must be removed from the film for grafting, the thickness of the chemical modification and can be controlled by means of phosphites. Atomicforce microscopy and wettability measurements showed that the grafted poly(acrylic acid) was heterogeneously distributed on the surface of the film, explaining the observed low reproducibility of the grafting reaction. However, we observed that the polarity of the surface was increased by the grafting. © 1995 John Wiley & Sons, Inc.     

Radiation-induced grafting of functional acrylic monomers onto polyethylene and polypropylene films using acryloyl chloride

Summary Radiation-induced graft polymerization of acryloyl chloride onto films of polyolefins (polyethylene and polypropylene) using gamma radiation was investigated in order to establish a convenient method to obtain polymer films grafted with polyacrylic esters. Grafting was carried out by three different methods; (i) direct irradiation of film in monomer solution (ii) vapor phase irradiation method, and (iii) pre-irradiation in air. The effects of monomer concentration, radiation dose and methods of grafting, on the formation of grafted polyolefins are reported in this paper. Received: 5 April 2000/Revised version: 17 November 2000/Accepted: 20 November 2000     

The Effect of Interparticle Stresses on Debonding in Spherical Silica Particle-Filled Composites with a Poly(vinyl butyral) Matrix

The effect of varying the volume fraction of 650 μm glass beads in a poly(vinyl butyral) matrix on the level of debonding in the particulate composites at a given applied tensile stress was investigated. Both clean beads and ones surface treated with the adhesion promoter 3-aminopropyltriethoxysilane were used. A model was developed to predict the observed behavior, based on Goodier's analytical solution for the stress concentration developed by a single sphere in an infinite matrix and the superposition of stress concentrations. By increasing the volume fraction of glass beads the average interparticle distance is decreased, leading to an increase of the overlap of the stress concentration fields surrounding the beads, thus causing debonding at a lower applied stress. The use of an adhesion promoter increased the maximum local stress required to cause debonding, but had no effect on the interparticle stress fields so the same trends, at higher applied stress, were observed. The model, although quite simple, showed good agreement with the experimental results for the dependence of the particle–matrix debonding behavior on the volume fraction of beads.     

Study on grafting maleic anhydride onto polypropylene in microcolloid systems by coirradiation

Grafting of maleic anhydride (MAH) onto polypropylene (PP) performed in microcolloid systems by coirradiation was studied in this paper. First, the microcolloid of PP and MAH in xylene was prepared and its dynamic light scattering (DLS) shows particle size distributions of microcolloid system in 4–6 μm. Second, the effect of irradiation dose and monomer concentration on the amount of grafted MAH was investigated. The results show that the coirradiation in microcolloid systems can obviously cause an increase of the amount of grafted MAH. The percentage of grafting of the product amounts to 5.24%. The molecular structures of grafted MAH prepared were characterized by Fourier-transform infrared spectroscopy. Differential scanning calorimetry and wide-angle X-ray diffraction were used to determine the degree of crystallinity and crystalline structure. POLYM. ENG. SCI., 47:1703–1707, 2007. © 2007 Society of Plastics Engineers     

Inorganic silica functionalized with PLLA chains via grafting methods to enhance the melt strength of PLLA/silica nanocomposites

The low melt strength greatly limits the application of PLA as biodegradable package materials produced by film blowing method. Modified silica nanoparticles are introduced into PLA matrix to solve this problem in this study. To build Poly (l-lactide) nanocomposites successfully, two kinds of convenient and efficient methods are conducted to synthesize well-defined topological PLLA grafted SiO₂ nanoparticle. One is the ring-opening of l-lactide (Grafting from), and another is nucleophilic addition reaction (Grafting to). The structure, molecular weight of grafted PLLA chains, grafting density, and the thermal decomposition behavior of the nanoparticles prepared by different methods are characterized. By varying the contents of the initiator SiO₂ and the molecular weight of the reacted PLA chains, high density-low molecular weight PLLA grafted SiO₂ are obtained in “grafting from” while high molecular weight-low grafting density PLLA grafted SiO₂ are synthesized in “grafting to”. It is exactly in good agreement with the theoretic model. The spatial distribution of nanoparticles as well as the interaction force between nanoparticles and matrix is critical important to structuring bionanocomposites with desirable properties. So the two kinds of synthesized nanoparticles are introduced into PLA matrix in our contribution to evaluate these two factors, respectively. The TEM and SEM results both reveal the uniform dispersion of nanoparticles after modified. While the extension and shear rheology results show that the long grafted chains covalently connected on the surface of the silica via “grafting to” contribute more to enhance the melt strength of PLA. Meanwhile, stabilized PLA nanocomposites films with modified silica via “grafting to” method are successfully blown base on these researches. The research in this work constitutes a robust way to design melt-strengthen PLA/SiO₂ nanocomposites.     

Radiation grafting of vinyl monomers onto wood pulp cellulose. Part I

The effect of dose, dose rate, monomer type, and monomer concentration on the water transport behavior in grafted cellulose pulp and hand sheets was studied. At low dose rates, grafting rates of styrene onto wood pulp were less with hand sheets than with the pulp itself. Grafting was also found to be decreased by increasing the dose rate. Grafting mixtures of styrene and acrylonitrile gave better yields than styrene alone. Excellent grafting yields were obtained by treating the pulp or hand sheets with water before adding vinyl monomers. In this way, solvents such as dioxane could be eliminated from the grafting mixture. The hand sheets, grafted with mixtures of acrylonitrile and styrene, had good mechanical properties although less than the corresponding ungrafted sheets. Grafting decreased the moisture regain in pulp and hand sheets. Gamma irradiation of wood pulp under ambient conditions without additives reduced the water sorption considerably.     

Factors affecting photografting of methacrylic acid on polyethylene film in liquid phases system

Factors affecting photografting (λ > 300 nm) of methacrylic acid on low-density polyethylene film were investigated in liquid-phase system with water. Benzophenone was used as a sensitizer by coating it on the film surface. Factors examined were monomer concentration (1.3 wt% to 10.0 wt%), polymerization temperature (30°C to 70°C), and film thickness (30 μm and 80 μm). It was found that grafted polymer is formed preferentially as compared with homopolymer under conditions such as monomer concentration higher than 6.0 wt%, polymerization temperature higher than 50°C, and film thickness of 30 μm. The structure of the grafted samples obtained in the above systems was characterized by the grafted chains distributing over the film and the flat appearance of film surface. In the grafting systems using the monomer concentration lower than 6.0 wt%, the polymerization temperature lower than 50°C, and the film thickness of 80 μm, homopolymer was formed predominantly. The resultant grafted chains localized mainly on the film surface, which appeared to be grainy.