Hypothesis: The primary method for recycling waste tires is grinding them into fine particles and then mixing them with various matrices to improve their properties. For example, ground tire rubber (GTR) can be used to enhance the impact resistance of brittle polymers such as polystyrene (PS). However, weak interactions between the two components may lead to a decline in mechanical properties. Polymer grafting onto GTR is a successful method for rubber modification. The unique advantage is the graft polymer can be selected based on the matrix polymer. Namely, polystyrene grafted onto the surface of GTR, PS-g-GTR, can be used as a compatibilizer for the PS/GTR blend. Methods: In this study, styrene monomer was in-situ polymerized in the presence of GTR to synthesize PS-g-GTR in bulk and solution environments. The variation in monomer conversion and grafting efficiency was investigated by increasing the temperature in bulk polymerization and increasing the initiator concentration in solution polymerization. Findings: The highest grafting efficiency (57%) and grafting degree (247%) were achieved in solution polymerization at 90 °C, with a molar ratio of initiator to monomer equal to 1% and a weight percentage of GTR to monomer equal to 13. A comparison of Fourier Transform Infrared Spectroscopy (FT-IR) spectra for GTR and PS-g-GTR clearly showed the appearance of peaks corresponding to benzene rings after grafting. Based on thermogravimetric analysis (TGA), the synthesized PS-g-GTR contained 56% polystyrene by weight. By calculating the cooperatively rearranging region (CRR) length scale at the glass transition temperature using differential scanning calorimetry (DSC), the molecular weight of the grafted chains was estimated to be greater than 104 g mol-1. This graft polymer appears to significantly improve the impact resistance of PS by enhancing compatibility between polystyrene and GTR.

The graft copolymerization of sodium acrylate onto chitosan in alkali medium was investigated, using redox system, potassium diperiodacuprate(III) (DPC) chitosan. The graft copolymer was characterized by Fourier transform infrared spectra analysis, X-ray diffraction analysis, differential scanning calorimetric, thermogravimetric analysis, and scanning electron microscopy techniques. A tentative mechanism is proposed to explain the generation of radicals and the initiation. The effects of reaction variables, such as the initiator concentration, the ratio of monomer to chitosan, and pH, as well as, reaction temperature and time were investigated, and the grafting conditions were optimized. Graft copolymer with high grafting efficiency was obtained, which indicated that DPC chitosan redox system is an efficient initiator for this graft copolymerization. The graft copolymer was used as the compatibilizer in blends of poly(methyl methacrylate) (PMMA) and chitosan. The scanning electron microscope micrographs indicated that the graft copolymer improved the compatibility of the blend. At the same time, the blend is expected to improve the biodegradability of the PMMA.

A copolymer composed of styrene and acrylonitrile was grafted onto cellulose backbone by free radical polymerization and atom transfer radical polymerization (ATRP) method. First, styrene was grafted onto cellulose Fibers by using suspension polymerization and free-radical polymerization technique. Potassium persulfate (PPS) was used as a chemical initiator and water was used as a medium. We used cellulose-graft-polystyrene as a starting polymer and N-bromosuccinimide (NBS) as a brominating agent to obtain polymers with bromine group. This brominated cellulose fibers were used as an ATRP macroinitiator. This macroinitiator can polymerize acrylonitrile in the presence of CuCl / 2, 2'-Bipyridine (Bpy) catalyst system, in THF solvent at 90oC. The formation of the graft copolymer was confirmed with FTIR, XRD, SEM, TGA and DSC methods.

Nitroxide-mediated free radical polymerization (LREP) was employed for the first time to prepare graft copolymer by having arylated polypropylene (Cl-PP) as a backbone and polystyrene (PS) as branches. The graft copolymerization of styrene was initiated by arylated PP carrying 2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPO) groups as a macroinitiator. Thus, maleic anhydride was grafted onto polypropylene by peroxide-catalyzed swell grafting method (PP-MAH). Next, PP-MAH reacted with ethanolamine to produce a hydroxyl group containing polypropylene (PP-OH) and the obtained PP-OH was treated with α-phenyl chloroacetyl chloride and converted to a chloroacetyl group containing polypropylene (PP-Cl). Finally, 1-hydroxyl-2, 2, 6, 6-tetramethylpiperidine (TEMPO-OH) was synthesized by reducing TEMPO with sodium ascorbate and this functional nitroxyl compound was coupled with a-phenyl chloroacetylated polypropylene. The resulting macroinitiator (PP-TEMPO) for free radical polymerization was then heated in the presence of styrene for the formation of the graft copolymer. The prepared graft copolymer was characterized by Fourier transform infrared spectroscopy and 1H NMR techniques. Glass transition temperature of grafted copolymer was investigated using thermogravimetric analysis and differential scanning calorimetric techniques. This approach using nitroxide-mediated macroinitiators is an effective method for the preparation of new materials.

This study deals with the synthesis and characterization of polyacrylonitrile (PAN)-grafted silica composite particles by emulsion graft polymerization using potassium persulphate as the initiator and Tween 80 as the surfactant for potential application in wastewater treatment. The commercially available silica particles (35-70 micron) were first functionalized with vinyltriethoxysilane that were subsequently employed for the grafting of PAN via emulsion polymerization. The effect of various experimental parameters, such as varying the amount of the monomer, initiator, and the emulsifier in the feed on the grafting (%) has been investigated in detail. The maximum grafting (296%) was achieved with 6% (w/v) monomer, 0. 15% (w/v) initiator, and 1% (w/v) emulsifier concentration. The nitrile groups of the PAN-grafted silica composite particles were converted into amidoxime by treating with hydroxylamine. The synthesized products in all the preparation steps were carefully characterized by various analytical tools, i. e., Fourier Transform InfraRed (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD) analysis. In the FT-IR spectrum of the silica-grafted PAN, the appearance of the characteristic peak at 2245 cm-1 that corresponds to CN stretching confirms the successful grafting of PAN onto the modified silica particles; while the transformation of nitrile into amidoxime functionality was verified by the appearance of peaks at 1642 cm-1 and 920 cm-1. Further verification of the grafting of PAN and amidoxime formation also comes from the SEM micrographs and the XRD profiles. Finally, the obtained amidoxime-grafted silica composite particles were evaluated as an adsorbent for Cu+2 ions from the simulated wastewater for potential application in wastewater treatment. The maximum adsorption capacity of 130 mg/g was achieved at pH 5 in 2 hrs.

A new potassium persulfate redox system has been investigated for the graft polymerization of vinyl monomers. In this study potassium persulfate system was used for initiation the polymerization. Graft polymerization of acrylonitrile (AN) onto starch (Sta) was carried out in aqueous solution using potassium persulfate (I) redox system. It was found that the percentage of grafting and rate of grafting were all dependent to some extent, on the concentration of the I, AN, Sta and Sta/ water as well as reaction time and temperature. The kinetics of the graft polymerization of AN onto Sta in aqueous solution was studied by Kjeldahl method (quantity and qualitative determination nitrogen content), and the kinetics of AN homopolymerization in the same system was studied by bromometry titration (residue monomer determination). The following rate expression (rate of graft polymerization and rate of homopolymerization) Rg=k·[AN]1.185·[I]0.499·[Sta]0.497 and Rh=k·[AN]1.359·[I]0.436 were obtained and a suitable mechanism was suggested. The graft copolymer was investigated with an infrared spectroscope. The overall activation energy was found to be 56.95 kJ/mol within the temperature range of 40-65°C.