Hala F. Naguib

Gamma radiation induced graft copolymerization of vinylimidazole-acrylic acid onto polypropylene films

Comonomers of vinylimidazole (VI) and acrylic acid (AA) have been grafted onto Polypropylene (PP) films using γ-radiation. The effect of the comonomer composition on the percent graft was investigated. The reactivity ratio of the prepared copolymers was determined by conventional methods. IR spectroscopy, surface morphology, mechanical properties, dyeability, as well as thermal stability of the grafted samples were also studied.

Chemically Induced Graft Copolymerization of Itaconic Acid onto Sisal Fibers

Itaconic acid (IA) was grafted onto sisal fibers using potassium persulfate as initiator. The effect of the monomer, initiator concentration, and reaction temperature on the grafting percentage has been investigated. Evidence of the grafting process has been shown using IR spectroscopy and a scanning electron microscope. The tensile strength and thermogravimetric analyses for ungrafted and grafted samples with various degrees of grafting have also been investigated. The effect of grafting percent on the dyeability of grafted sisal fibers with basic dye has been studied.

Copolymerization of Methyl Methacrylate with N-Phenylmaleimide in Different Solvents

Abstract The copolymerization of methyl methacrylate (MMA) and N-phenyl-maleimide (NPMI) in various solvents has been studied. It has beerr shown that monomer-monomer interaction exists and leads to the formation of a weak charge-transfer complex (CTC). The CTC concentration is found to depend on the type of solvent, and its equilibrium constant depends on the dielectric constant of the solvent and increases in the order DMSO < chloroform < benzene < CC14. NMR and dipole moment measurements have been used to investigate interaction between the monomers. The monomer reactivity ratios are found to vary appreciably with the type of solvent. The data obtained indicate that changes in the reactivity ratios are due to monomer solvation or to the solvent effect on the propagating radical, rather than to the participation of the CTC in the propagation step.

Polymerization behaviour of a new vinyl thiourea derivative

Abstract 1-Methacryloyl-3-phenylthiourea (MAPTU) has been prepared and polymerized by a free-radical mechanism. The polymer formed has low molecular weight. The kinetic orders of the polymerization with respect to monomer and initiator, as well as the overall activation energy, were measured and found to be those expected for a free-radical scheme. This new monomer showed a tendency for cyclization to give a six-membered heterocycle. The effects of temperature and solvent on the rate of cyclization have been studied. MAPTU monomer and its homopolymer were found to form complexes with several metal ions. The stability constants of several phenyl-substituted MAPTU with Cu were measured and a correlation between log K X K H and the Hammett constant was established. The MAPTU-Cu and polyMAPTU-Cu complexes were prepared and their stability constants were calculated. MAPTU was copolymerized with styrene and acrylonitrile. The reactivity ratios have been calculated by several methods.

Preparation and Characterization of Biodegradable Polyurethane Nanocomposites Based on Poly(3-hydroxybutyrate) and Poly(Butylene Adipate) Using Reactive Organoclay

Polyurethane nanocomposites were synthesized using one-step solution polymerization of poly(3-hydroxybutyrate)-diol, poly(butylene adipate)-diol using 1,6-hexamethylene diisocyanate. Nanocomposites were prepared using an in-situ polymerization method. The structure was verified using FTIR and 1HNMR. Morphology was examined by XRD and TEM methods. Thermal properties were examined using DSC and TG. DSC showed that all samples were semicrystalline. The Cloisite 30B enhanced the melt crystallization of PHB segments while hindering those of the PBA segments. Thermal stability was improved compared to the neat PUs samples. The Coats-Redfern model was used to calculate the activation energy. Mechanical properties were improved with incorporation of organoclays.

Effect of Organo-Modified Montmorillonite on Thermal Properties of Bacterial Poly(3-hydroxybutyrate)

Nanocomposites based on biodegradable poly(3-hydroxybutyrate) (PHB) and two types of organically modified layered silicates, cloisite 30B (C30B) and montmorillonite grafted-poly(ϵ-caprolactone) (MPCL), were prepared through solution intercalation technique. The thermal properties of PHB/nanocomposites at different organoclay contents (5 and 10%) were investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results showed that the dispersed MPCL enhanced the rate of crystallization of PHB from glassy and molten states, whereas C30B retarded the crystallization of PHB from glassy state and enhanced its crystallization from molten state. Kinetics of thermal degradation was studied using Ozawa and Kissinger methods.

Electrical Conductivity and Dielectric Behavior of Some Poly(Alkyl Methacrylate)s/Polyvinylpyrrolidone Blends

Abstract A systematic dielectric study over a frequency range of 100 Hz up to 100 k Hz was carried out on some poly(alkyl methacrylate)s: poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), and poly(butyl methacrylate) (PBMA) blended with polyvinylpyrrolidone (PVP). The compatibility investigation, which was tested by using the dielectric method and confirmed by viscosity technique, led to a conclusion that both PMMA/PVP and PEMA/PVP blends are incompatible while PBMA/PVP blends are compatible. Tetrachlorophthalic anhydride (TCPA) was chosen to be added in increasing quantities (0%–30% by weight) to the investigated blends. Ten percent of such anhydride was found to solve the problem of phase separation between both incompatible blends. Moreover, the electrical conductivity of the investigated blends was found to increase linearly, in the semilogarithmic scale, by increasing TCPA content (10−12 to 10−5 S−1 cm−1). After subtraction of the losses due to dc conductivity, the dielectric data reveal a lower frequency absorption region, which is found to be unchanged by increasing either the blend ratio or the content of TCPA. This region ascribes the Maxwell-Wagner effect due to the difference in the permittivity and conductivities in polymeric materials. The higher values of ϵ″ in the higher frequency range for all the blends indicates a higher frequency absorption region with maximum frequency out of the available range of frequencies. The addition of TCPA shifts this maximum towards lower frequencies. This shift indicates an increase in the molar volume of the rotating units and consequently an increase in the relaxation time.

Polymerization and chelating behavior of N-acryloyl, N-phenylthiourea

SummaryThe title monomer has been prepared for the first time. It has been polymerized by a free radical mechanism in different solvents. Only oligomers were obtained so far. The dependence of the rate of polymerization on monomer and initiator concentrations has been measured and was found to follow the usual free radical scheme. The overall activation energy of polymerization has been measured in two solvents and was found to be 21.2 and 15.03 K.Cal/mol in tetrahydrofuran (THF) and N,N-dimethyl formamide (DMF) respectively. The prepared monomer has excellent chelating ability with different metal cations. The stability constant of the monomer with copper (II) ions has been measured in acetone as well as in dioxane. The complexes have no tendency for free radical polymerization.

Synthesis, Characterization, and Microbial Activity of Nanocomposites of Chitosan-Graft-Poly(4-vinyl pyridine) Copolymer/Organophilic Montmorillonite

Organophilic montmorillonite was synthesized by cationic exchange between Na+-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Nanocomposites of chitosan grafted with 4-vinyl pyridine and organophilic montmorillonite were prepared in acetic acid using ammonium persulfate as initiator. The molecular structure of the grafted copolymer was confirmed by FTIR. The degree of dispersion and the intercalation spacing of these nanocomposites were investigated using X-ray diffraction. The enhanced thermal stability of nanocomposites was verified by differential scanning calorimetry and thermogravimetric analysis. Preliminary results of the antibacterial and antifungal activities of the prepared nanocomposites have demonstrated significant antimicrobial activity of the nanocomposites compared with pure and grafted chitosan. GRAPHICAL ABSTRACT

Nanocomposites Based on Chitosan-Graft-Poly(N-Vinyl-2-Pyrrolidone): Synthesis, Characterization, and Biological Activity

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange between Na+-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Chitosan graft copolymer nanocomposites were synthesized by grafting N-vinyl-2-pyrrolidone onto chitosan in aqueous acetic acid in the presence of OMMT using free radical polymerization. The chemical structures were verified by FTIR. Scanning electron microscopy showed a surface roughness for chitosan graft nanocomposites. Wide-angle X-ray diffraction confirmed the intercalation of grafted chitosan chains between OMMT galleries. Thermogravimetric analysis indicated that the thermal stability of grafted chitosan was enhanced by OMMT incorporation. Preliminary studies showed that the nanocomposites exhibited antimicrobial activity compared with chitosan graft copolymer. GRAPHICAL ABSTRACT