Naeem M. El-Sawy

Improvement of antioxidant activity of chitosan by chemical treatment and ionizing radiation.

Modification of chitosan (CS) to N-maleoylchitosan (NMCS), N-phthaloylchitosan (NPhCS) and sulfonated-chitosan (SCS) was done using maleic anhydride, phthalic anhydride and chlorosulfonic acid, respectively followed by exposing them to γ-rays at different doses. The molecular weights and structural changes of irradiated chitosan derivatives were determined by GPC, FT-IR and UV-vis spectrophotometer. The molecular weights decreased with increasing irradiation dose. Results revealed that the main polysaccharide structure remained after irradiation. To investigate the enhancement of antioxidant activity of chitosan and its derivatives of different molecular weights, radical mediated lipid peroxidation inhibition, scavenging effect of DPPH radicals, reducing power and ferrous ion chelating activity assays were used. Chitosan derivatives with different molecular weights exhibit antioxidant activity. The lower the molecular weights of chitosan and its derivatives, the higher the antioxidant activity. NMCS possessed high scavenging effect on DPPH radicals compared with NPhCS, SCS and ascorbic acid. The irradiated chitosan and its derivatives could be used as natural antioxidants.

Radiation-induced graft polymerization of acrylic acid onto poly(tetrafluoroethylene-perfluorovinyl ether) copolymer films: complexation with some transition metals and biological activity

Abstract The radiation-induced grafting of acrylic acid onto poly(tetrafluoroethylene-perfluorovinyl ether) copolymer film was carried out to synthesize graft copolymer membranes of complexing ability with some selected transition metal ions such as Cr III , Mn II , Cu II , Ag I and Cd II . The complex formation of these graft copolymer–metal complexes was studied by atomic absorption spectroscopy, X-ray fluorescence, IR, UV and electron spin resonance spectrometry. The overall results suggest octahedral geometry for both Cr III and Mn II but square planar for Cu II . The results revealed the high stability of the obtained ligand–metal complexes. The biological activity of the grafted film and its complexes with various metal ions was investigated under the same conditions. Silver (I) complexed membrane had a strong biocidal effect for all tested bacteria. The biological activity for Cr III complex has been effected on E . coli and S . aureus , whereas the Cd II complex has its effect on E . coli , B . anthrax and B . cereus . The Cu II complex has only antifungal activity. No biological effect has appeared for both the grafted film or Mn II complexed one on either bacteria or fungi.

Physical properties of graft copolymer-metal complexes obtained by radiation grafting onto poly(tetrafluoroethylene-co-perfluorovinyl ether)

Abstract Grafting of aqueous acrylic acid onto poly(tetrafluoroethylene-co-perfluorovinyl ether) films has been carried out using γ-irradiation. Copper and chromium complexes have been prepared by treating the grafted films with aqueous solutions of copper and chromium sulphates. The formation of polymer/metal complexes has been confirmed spectrophotometrically by u.v. and colour measurements. Electrical and mechanical properties of films of the complexes have been studied. Thermal analysis and study of the effect of u.v. on the polymer metal complexes have been also undertaken.

Amidoximation of acrylonitrile radiation-grafted onto low-density polyethylene and its physicochemical characterization

Membranes were prepared by the direct radiation grafting of acrylonitrile onto low-density polyethylene films. These grafted membranes were amidoximated using hydroxylamine hydrochloride in basic medium. The influence of monomer concentration and swelling behaviour of grafted membrane, amidoximated grafted membrane, and its sodium salt were also studied. Amidoximated grafted membranes and their copolymer–metal complexes of Cu(II) or Cr(III) were prepared. These membranes were characterized using different analysis techniques such as IR, UV and ESR spectrometry. The UV and ESR analyses revealed that the geometry structure for Cu(II) is square planar, while for Cr(III) it is octahedral. The amidoxime ligand was used for separating metal ions from aqueous solutions by a complexation process. The thermal stability of different membranes was investigated through TG analysis. It was found that the amidoxime-grafted membranes possess good hydrophilic properties that may make them promising candidated for some practical applications such as the recovery of metals from their aqueous systems. © 2000 Society of Chemical Industry

Investigation of radiation‐grafted and radiation‐modified N‐vinyl‐2‐pyrrolidone onto polypropylene film

The radiation-induced graft copolymerization of N-vinyl-2-pyrrolidone (NVP) onto polypropylene films was investigated using the mutual method. The grafted polymer was modified with prepared α,β-unsaturated nitrile (Scheme 1). The water uptake of the grafted and modified grafted films was found to increase with the degree of grafting. It was observed that the swelling behavior of the modified grafted films with α-cyano-β-phenyl crotononitrile improved more than that of the film grafted and modified grafted with α-cyano-β-(2-thienyl)crotononitrile or α-cyano-β-(2-pyridyl)crotononitrile. The modification process for the grafted substrate was confirmed by IR spectroscopy. No significant improvement was observed in thermal stability for the modified grafted films compared to the grafted films. Scanning electron microscopy (SEM) of the grafted and modified grafted membranes heated to 150°C showed change in the structure and morphology. Improvement in the hydrophilicity and morphology of these membranes with carbonitriles may increase the permeability of those membranes for some practical applications.

Some investigations on radiation‐grafting of acrylic acid onto poly(tetrafluoroethylene–ethylene) copolymer films and its complex with copper salt solution

A study was made of the graft copolymers obtained by radiation-induced grafting of acrylic acid onto poly(tetrafluoroethylene–ethylene) (ET) films. The conversion of the graft copolymers (60wt%) into metal acrylate copolymer complexes was carried out by treatment with various concentrations of aqueous CuCl2. These graft copolymer–metal complexes were studied by IR, UV spectrometry, X-ray diffraction (XDR), and electron spin resonance (ESR). The effect of temperature on the trunk, untreated grafted and treated grafted copolymer films was investigated by IR and thermogravimetric (TG) analysis. The influence of metal complexes of Cu2+ ions on the thermal properties and electrical conductivity was determined. It is assumed that such materials may be of great interest in the field of semiconducting materials, in addition to their resistance to degradation under high temperature, up to 300°C.

Radiation-induced graft polymerization of acrylonitrile onto isotactic polypropylene and poly(tetrafluoroethylene-ethylene) copolymer films

Direct radiation-induced grafting of acrylonitrile (AN) onto both isotactic polypropylene (IPP) and (tetrafluoroethylene-ethylene) copolymer (ET) films has been studied. The effect of grafting conditions such as inhibitor and monomer concentrations and irradiation dose on the grafting yield was investigated. Homopolymerization of acrylonitrile was reduced to a minimum using ferric chloride (FeCl 3 ), and the suitable optimum concentration of the inhibitor was found to be 0.1 wt%. The higher the monomer concentration, the higher the degree of grafting obtained. It was observed that the degree of grafting onto IPP was higher than onto ET, at given grafting conditions. The effect of aging on IPP was also examined. IR spectroscopy showed that IPP was susceptible to photooxidation by aging. The swelling behaviour and electrical conductivity of the graft and hydrolysed graft films were investigated. The electrical conductivity was improved by hydrolysis of polyacrylonitrile in the graft chains.

Gamma irradiated chitosan and its derivatives as antioxidants for minced chicken.

Ionizing radiation and oxidizing agent like H2O2 were used to degrade chitosan (CS) and its derivatives; N-maleoylchitosan (NMCS), and N-phthaloylchitosan (NPhCS). The structure changes were detected using gel permeation chromatography (GPC). The results revealed that ionizing radiation degraded CS, MNCS, NPhCS and altered their molecular weights and antioxidant activity. The higher the irradiation dose, the lower the molecular weight and the higher antioxidant activity. The addition of irradiated CS and NMCS to minced chicken resulted in highly significant reduction in malondialdehyde (MDA) content (50 and 70%, respectively) if compared with the control. The irradiated NMCS toxicity study did not show strong proliferative effect at small concentrations or cytotoxic effects at higher concentrations. The obtained results suggested that CS and NMCS could be used as natural antioxidant for improving the oxidative deterioration of minced chicken during refrigerated storage. Irradiated NMCS has higher scavenging activity. NMCS could be used as antioxidant. Irradiated NMCS did not show proliferative or cytotoxic effects.

Complexation of rhodium on radiation-grafted acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether) copolymer films

Radiation-induced graft polymerization of acrylic acid onto poly(tetrafluoroethylene-perfluorovinyl ether) copolymer films has been prepared using y-irradiation by the mutual method. The grafted copolymer rapidly complexes with rhodium ions through the carboxylic groups. The complexation process was followed by measuring the variation of the pH of aqueous RhCl 3 solution of several concentrations as a function of time. Spectroscopic, electrical, optical, thermal, and diffraction measurements have been investigated. The results revealed the high stability of the ligand-metal complex formed. Thus, a practical application of the grafted copolymer in the field of rare metal waste treatment is implied.

Radiation induced crosslinking of polyacrylamide incorporated low molecular weights natural polymers for possible use in the agricultural applications

Superabsorbent hydrogels based on polyacrylamide (PAAm) and Na-alginate (Alg) or chitosan (CS) were synthesized by γ-rays. The effect of dose and copolymer composition on gel content and water absorbency of PAAm/Alg, PAAm/CS and PAAm/Alg/CS hydrogels were studied. The gel content and water absorbency follows the order PAAm/Alg>PAAm/Alg/CS>PAAm/CS. The effect of different cations, fertilizers, buffers on water absorbency of the hydrogels was investigated. Water retention capability of swollen hydrogels as a function of time was studied. PAAm/Alg hydrogel has a high water retention capability. An application of the prepared hydrogels in agricultural fields was performed using maize plants. The results showed that the presence of hydrogels had growth promotion effect on quality and quantity of maize plants. The plants treated by PAAm/Alg hydrogels showed 50% increase in the grain yield suggesting their possible use as a soil conditioner and a water reservoir for plant-soil system.