Preirradiation Grafting Research Articles

Asymmetric C–C bond formation with l-prolinol derived chiral catalysts immobilized on polymer fibers

N-(4-Vinylbenzyl)-α,α-diphenyl- l-prolinol was immobilized on polyethylene fibers by electron beam induced pre-irradiation grafting using styrene as a co-monomer. The resulting polymer supported catalyst P2 was utilized in asymmetric C–C bond forming reactions and its performance compared with those of previously prepared fibrous cross-linked α,α-diphenyl- l-prolinol P1 and homogeneous model compounds. The fibrous catalyst yields similar enantioselectivities in the asymmetric addition of diethylzinc to benzaldehyde as its homogeneous reference reaction and can be recycled with minimal loss of activity. When P2 was used as the catalyst in the addition of phenylacetylene to benzaldehyde, the corresponding propargylic alcohol was obtained with enantiomeric excesses of up to 91%.

UV‐radiation–induced preirradiation grafting of methyl methacrylate onto lignocellulose fiber in an aqueous medium and characterization

AbstractThe preirradiation method of grafting has been established by ultraviolet radiation. Methyl methacrylate (MMA) was grafted onto jute fiber in an aqueous medium. The variation of graft weight with UV‐radiation time, monomer concentration, and reaction time was investigated. The conversion of monomer into homopolymer and graft copolymer was evaluated. The graft weight passes through a maximum value (∼ 122%) with UV‐radiation time. The optimum value of the monomer concentration was evaluated for maximum degree of grafting. Graft copolymerization of MMA onto lignocellulose fiber significantly increases the elongation at break (∼ 65%) compared to that of the “as‐received” sample. However, a linear decrease on breaking load was observed with the increase of graft weight. The estimation of degree of grafting was achieved using an IR technique by correlating band intensities with the degree of grafting. Considering the water‐absorption property, the grafted sample showed a maximum up to 61% decrease in hydrophilicity compared to that of the as‐received sample. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1667–1675, 2004

Surface modification of polypropylene film by radiation‐induced grafting and its blood compatibility

AbstractTo endow blood‐compatible properties onto polypropylene (PP) film, we grafted 2,3‐epoxypropyl methacrylate (EPMA) to PP film with a preirradiation grafting technique and then introduced various functional groups onto the grafted PP film. The EPMA grafting extent was dependent on the absorbed dose, reaction time, and temperature. The reactions of hydroxylation, iminodiacetation, sulfonation, phosphonation, and amination were performed under various conditions to introduce functional groups into the epoxy group of EPMA‐grafted PP films, respectively. We also immobilized heparin on aminated PP film to compare blood compatibility with various functionalized samples. The grafting, functionalization, and heparinization reaction were confirmed by Fourier transform infrared spectroscopy in the attenuated total reflectance mode and electron spectroscopy for chemical analysis. The blood compatibility of various functional groups and heparin‐introduced samples as well as control samples was examined by the determination of platelet adsorption and thrombus formation. For the examination of the blood compatibility of functionalized PP samples, acid citrate dextrose human whole blood and platelet‐rich plasma were used. The amount of the formed thrombus and the adherent platelets on functionalized PP sample surfaces were evaluated by an in vitro method following Imai and Nose's technique and by scanning electron microscopy, respectively. The blood compatibility of various functional‐group‐introduced PP films after grafting was better than that of the PP control. Phosphoric‐acid‐group‐ and heparin‐introduced PP films had especially good blood compatibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1726–1736, 2003

Synthesis of a new type of adsorbent containing carboxyl and amidoxime groups by preirradiation grafting and its absorption of metal ions

Synthesis of a new type of adsorbent containing carboxyl and amidoxime groups by preirradiation grafting and its absorption of metal ions

Synthesis and characterisation of sulfonic acid-containing ion exchange membranes based on hydrocarbon and fluorocarbon polymers

Radiation-induced graft copolymerisation has been used to modify polymers with styrene to prepare pre-cursor copolymers that can be subsequently functionalised to produce ion exchange membranes. This paper describes the processes of simultaneous and pre-irradiation graft copolymerisation of styrene to modify hydrocarbon and fluorine-containing polymers and their sulfonation to produce hydrophilic membranes. The effect of varying the grafting conditions and their characterisation by ion exchange capacity, electrolytic resistivity and equilibrium water content is reported.

Synthesis of a new type of adsorbent containing carboxyl and amidoxime groups by preirradiation grafting and its absorption of metal ions

Synthesis of a new type of adsorbent containing carboxyl and amidoxime groups by preirradiation grafting and its absorption of metal ions

Synthesis of a new type of adsorbent containing carboxyl and amidoxime groups by preirradiation grafting and its absorption of metal ions

AbstractA new type of adsorbent containing amidoxime and carboxyl groups was synthesized by the preirradiation graft copolymerization of acrylonitrile (AN) and acrylic acid (AA) onto fibrous‐type poly(vinyl alcohol) followed by amidoximation with hydroxylamine. The radiation dose and ratio of AN and AA monomers influenced the degree of grafting, the content of the amidoxime group, and the adsorption capacity. The synthesis course, structure, and properties of the adsorbent were investigated with Fourier transform infrared, scanning electron microscopy, and thermogravimetry. The adsorption property of the adsorbent for palladium(II) ions was also studied systematically. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1986–1992, 2002

Synthesis of proton‐conducting membranes by the utilization of preirradiation grafting and atom transfer radical polymerization techniques

AbstractThe atom transfer radical polymerization (ATRP) of styrene onto poly(vinylidene fluoride)‐graft‐poly(vinylbenzyl chloride) (PVDF‐g‐PVBC) membranes was investigated. Novel membranes were designed for fuel‐cell applications. The benzyl chloride groups in the PVDF‐g‐PVBC membranes functioned as initiators, and a Cu‐based catalytic system with the general formula Cu(n)Xn/ligand [where X is Cl or Br and the ligand is 2,2′‐bipyridyl (bpy)] was employed for the ATRP. In addition, 10 vol % dimethylformamide was added for increased solubility of the catalyst complex in styrene. The system was homogeneous, except for the membrane, when the initiator/copper halide/ligand/monomer molar ratio was 1/1/3/500. As anticipated, the fastest polymerization rate of styrene was observed with the copper bromide/bpy‐based catalyst system. The reaction rate was strongly temperature‐dependent within the studied temperature interval of 100–130 °C. The degree of grafting increased linearly with time, thereby indicating first‐order kinetics, regardless of the polymerization temperature. Furthermore, 120 °C was the maximum polymerization temperature that could be used in practice because the membrane structure was destroyed at higher temperatures. The degree of styrene grafting reached 400% after 3 h at 120 °C. Such a high degree of grafting could not be reached with conventional uncontrolled radiation‐induced grafting methods because of termination reactions. On the basis of an Arrhenius plot, the activation energy for the homogeneous ATRP of styrene was 217 kJ/mol. The prepared membranes became proton‐conducting after sulfonation of the polystyrene grafts. The highest conductivity measured for the prepared membranes was 70 mS/cm, which is comparable to the values normally measured for commercial Nafion membranes. The scanning electron microscopy/energy‐dispersive X‐ray results showed that the membranes had to be grafted through the matrix with both PVBC and polystyrene to become proton‐conducting after sulfonation. In addition, PVDF‐g‐[PVBC‐g‐(styrene‐block‐tert‐butyl acrylate)] membranes were also synthesized by ATRP. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 591–600, 2002; DOI 10.1002/pola.10146

Immobilization of chiral ligands on polymer fibers by electron beam induced grafting and applications in enantioselective catalysis.

[reaction: see text] Styrenic TADDOL and L-prolinol-derived monomers were immobilized on polyethylene fibers by electron beam induced preirradiation grafting using styrene as comonomer. The polymer-supported chiral ligands were utilized as catalysts in the asymmetric addition of diethylzinc to benzaldehyde. Fiber-bound titanium TADDOLate gave a quantitative conversion of benzaldehyde to 1-phenylpropan-1-ol in a 97:3 S/R enantiomeric ratio. The catalyst was successfully regenerated and employed in subsequent reactions with retention of high enantioselectivities.

Study on antithrombosis dialytic membrane prepared by preirradiation grafting

A new antithrombosis dialytic membrane with a hydrophilic–hydrophobic microphase structure was prepared by preirradiation grafting of β-hydroxyethyl methacrylate (HEMA) and styrene (St) onto ethylene–vinyl acetate (EVA). The influence of some effects, such as preirradiation dose, dose rate, grafting reaction temperature, reaction time, and monomer component, on the degree of grafting was determined, and the properties of the grafted films were investigated. Compared with the conventional EVA-grafted hydrophilic monomer, the EVA films grafted with HEMA and St have superior antithrombogenicity; the antithrombogenicity and permeability of EVA-g-(HEMA-co-St) were 30 and 20 times higher than those of the ungrafted films, respectively, when the volume ratio (HEMA versus St) was about 7:3. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1321–1327, 2000

Reduction of the Thrombogenicity of Polyethylene Membranes by Radiation Grafting

A new anti-thrombosis dialytic membrane with a hydrophilic-hydrophobic microphase structure was prepared by pre-irradiation grafting of β-hydroxyethyl methacrylate (HEMA) and styrene (St) onto polyethylene (PE) membranes. The effects of reaction conditions on the degree of grafting were determined, and the properties of the grafted films were investigated. Compared with PE grafted with hydrophilic monomer, the antithrombogenicity and permeability of the PE-g-(HEMA-co-St) were 30 and 15 times higher than that of the ungrafted films, respectively, if the volume ratio (HEMA:St) is about 1:1.

Preparation of thermosensitive hydrogel (PP-g-NIPAAm) with one–off switching for controlled release of drugs

A novel thermosensitive hydrogel with high mechanical strength was obtained by grafting N-isopropylacrylamide (NIPAAm) onto polypropylene using a preirradiation grafting method. The effect of radiation dose, dose rate, grafting temperature and reaction time on the grafting degree and properties of swelling-deswelling is discussed. Water absorption of the grafted polypropylene film could be switched on and off swiftly by control of temperature. The microstructure of grafted ultra thin porous PP film was studied with scanning electron microscope. (C) 1999 Elsevier Science Ltd. All rights reserved.

Phase separation and crystallinity in proton conducting membranes of styrene grafted and sulfonated poly(vinylidene fluoride)

A series of proton exchange membranes have been prepared by the preirradiation grafting method. Styrene was grafted onto a matrix of poly(vinylidene fluoride) (PVDF) after electron beam irradiation. Part of the samples was crosslinked with divinylbenzene (DVB) or bis(vinylphenyl)ethane (BVPE). Subsequent sulfonation gave membranes grafted with poly(styrene sulfonic acid) and marked PVDF-g-PSSA. It was found that the intrinsic crystallinity of the matrix decreased in both the grafting and the sulfonation reaction in all the membranes. The graft penetration and the ion conductivity are influenced strongly by the crosslinker. The ion conductivity is considerably lower in crosslinked membranes than in noncrosslinked ones. Generally, the mechanical strength decreases with crosslinking. The membranes show a regular phase separated structure in which the sulfonated grafts are incorporated in the amorphous parts of the matrix polymer. The phase separated domains are small, of the order of magnitude of 100–250 nm. These were resolved on transmission electron micrographs and on atomic force images but could not be resolved with microprobe Raman spectroscopy. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1741–1753, 1999

Grafting copolymerization of acrylamides onto preirradiated PP films

Acrylamide (AAm), N,N-Dimethylacrylamide (DMAAm) and N-(3-Dimethylaminopropyl) methacrylamide (DMAPMAAm) were grafted onto polypropylene (PP) films by preirradiation grafting respectively. The effect of irradiation dose, solvent systems and reaction time on the degree of grafting were determined. The grafted sample films were verified by Fourier Transform Infrared (FTIR) spectroscopy in the attenuated total reflectance mode (ATR) and the determination of water contact angle. The blood compatibility of the grafted PP films were evaluated by the determination of platelet adsorption and thrombus. The blood compatibility of grafted PP films seems better than that of original PP films.

Grafting copolymerization of polyethylene glycol methacrylate (PEGMA) onto preirradiated PP films

Polyethylene glycol methacrylate (PEGMA) with different polyethylene oxide units were grafted onto polypropylene (PP) films by a preirradiation grafting method. The effect of co-solvent system on the degree of grafting and water contact angle were determined, respectively. The grafted sample films were verified by Fourier Transform Infrared (FTIR) spectroscopy in the attenuated total reflectance mode (ATR). The biocompatibility and blood compatibility of the grafted PP films were evaluated by the determination of protein adsorption, platelet adsorption and thrombus.

Pre-irradiation grafting of temperature sensitive hydrogel on cotton cellulose fabric

Abstract Temperature sensitive polymer (poly-N-isopropylacrylamide)was grafted on the surface of cotton cellulose fabric by γ -pre-irradiation-induced grafting. The effect of absorbed dose, dose rate, grafting temperature and concentration of monomer on grafting yields were investigated. In order to explain the characteristic of active points and the location of grafting site, the peroxides formed during irradiation in air and the effects of store time at various temperatures after irradiation were measured. It was found that grafting reaction was induced mainly by trapped radicals located in the interphase between crystal and amorphous regions, but for the monomer of N-isopropylacrylamide the peroxides also made some contribution to grafting yields. The results showed that the surface of grafted fabric has temperature sensitivity as well.

Preirradiation grafting of ethylene vinyl acetate copolymer resins

Abstract Acrylic acid was graft copolymerised on to EVA powdered resins containing 9%, 18% and 28% vinyl acetate. A preirradiation grafting method was used and the effect on graft level of varying the parameters of gamma irradiation dose (2–50 kGy), dose rate (0.5–5 kGy h −1 ), monomer concentration (2.5–25%) and grafting time (1–4 h) and temperature (35–98°C) was investigated. The graft copolymer resins were converted into film and characterised in terms of their hydrophilicity and electrolytic resistance in alkaline solutions. Depending on the vinyl acetate content and rheological properties of the base EVA copolymer, high graft weight resins can be converted into semipermeable films suitable for a range of applications including battery separator membranes and topical medical dressings.

Radiation grafting of thermo-sensitive poly(NIPAAm) onto silicone rubber

Pre-irradiation grafting of poly(NIPAA)m on silicone rubber was successfully completed. It was found that the graft reaction could be done at higher temperature and induced by peroxides produced during irradiation of samples in air. Production and decomposition of the peroxides were investigated. The activation energy of peroxides decomposition equals 27.2 kJ/mol. The study of grafting kinetics at various temperature showed the graft reaction is easy to carry out at higher temperature because the activation energy of graft reaction is 54.7 kJ/mol. Some results of direct radiation polymerization in this system were also given. The surface of the grafted films had thermal sensitivity and the LCST of them closed to 35°C. The surface morphology and the swelling behaviors of the samples were observed.

Graft copolymerization of polyethylene glycol methacrylate onto polyethylene film and its blood compatibility

In an attempt to produce surfaces that show low levels of adsorption of protein and adhesion of platelets, different molecular weights of polyethylene glycol methacrylate (PEG-MA) were grafted onto polyethylene film by a preirradiation grafting process. The extent of grafting was found to be dependent on the storage condition of the irradiated polyethylene film, the preirradiated dose, reaction time and temperature, molecular weight of PEG-MA, and the type of solvent. The grafting yield was found to decrease rapidly with storage time for irradiated polyethylene film stored at room temperature. On the other hand, the grafting yield in the irradiated polyethylene stored at −130°C remained nearly constant up to 20 days after irradiation. The grafting yield decreased with an increased PEG-MA molecular weight. Human plasma protein was adsorbed onto control and PEG-MA-grafted polyethylene film surfaces, and the relative adsorbed amount of proteins on the surfaces was evaluated by electron spectroscopy for chemical analysis. The adsorbed protein and platelet adhesion on the polyethylene film surface decreased rapidly with the grafting yield. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 631–641, 1999

Feasibility study on the melt processing of radiation-grafted ethylene-vinyl acetate copolymer resins

The feasibility of melt processing radiation-grafted polymer powder was investigated by preirradiation grafting of acrylic acid onto ethylene–vinyl acetate (EVA) copolymer resins containing 9, 18, and 28% by weight vinyl acetate. The relationship between graft weight and melt processability was determined from melt flow index (MFI) measurements. Films were obtained by both compression molding and extrusion and were characterized in terms of their hydrophilicity. The limiting value for graft level for processability was found to be in the region of 30–35% at the two extremes of the range of MFI values of the base polymer. The preferred polymer has an MFI of 35 dg/min, giving a limiting maximum graft weight for processability of 45%. It was demonstrated that high graft weight EVA copolymer resins are melt processable and that this would be a viable method for the production of hydrophilic membranes for applications such as drug delivery membranes, medical devices, including catheters and stents and, semipermeable battery separator membranes. © 1999 John Wiley & Sons, Inc. Adv Polym Techn 18: 343–350, 1999