The rich chemistry of polybenzoxazines allows a wide range of molecular structure design by using appropriate starting materials. A new class of polybenzoxazines has been developed from benzoxazine monomers containing pendent long aliphatic chains. The monomers have been synthesized by the reaction of phenol or bisphenol A with two different long-chain aliphatic amines. The chemical structure of the monomers was confirmed by 1 H nuclear magnetic resonance and Fourier transform infrared spectroscopy. The polymerization behavior of the monomers studied by differential scanning calorimetry shows exothermic peaks due to the ring-opening polymerization of benzoxazine monomers centered at 247-255 • C. Dynamic mechanical analysis indicated that the glass transition temperatures T g were in the range 81-92 • C. The thermal stability of the polymers was also examined by thermogravimetric analysis, demonstrating that the weight loss temperatures decreased in comparison with that of traditional polybenzoxazine.
A different series of new polystyrene-clay nanocomposites have been prepared by grafting polymerization of styrene with vinyl-montmorillonite (MMT) clay. The synthesis was achieved through two steps. The first step is the modification of clay with the vinyl monomers, such as N,N-dimethyl-n-octadecyl-4-vinylbenzyl-ammonium chloride, n-octadecyl-4-vinylbenzyl-ammonium chloride, triphenyl-4-vinylbenzyl-phosphonium chloride, and tri-n-butyl-4-vinylbenzyl-phosphonium chloride. The second step is the polymerization of styrene with different ratios of vinyl-MMT clay. The materials produced were characterized by different physical and chemical methods:(1) IR spectra, confirming the intercalation of the vinyl-cation within the clay interlayers; (2) thermogravimetric analysis (TGA), showing higher thermal stability for PS-nanocomposites than polystyrene (PS) and higher thermal stability of nanocomposites with of phosphonium moieties than nanocomposites with ammonium moieties; (3) swelling measurements in different organic solvents, showing that the swelling degree in hydrophobic solvents increases as the clay ratio decreases; (4) X-ray diffraction (XRD), illustrating that the nanocomposites were exfoliated at up to a 25 wt % of organoclay content; and (5) scanning electron microscopy (SEM), showing a complete dispersion of PS into clay galleries. Also, transmission electron microscopy (TEM) showed nanosize spherical particles of $ 150-400 nm appearing in the images.
Polymer-clay composite material has been prepared by intercalation of polymeric ammonium salt onto the montmorillonite (Na-MMT) followed by grafted polymerization of hydroxyethyl methacrylate onto amine-terminated poly(butadiene-co-acrylonitrile)-montmorillonite (ATBN-MMT) intercalate. The hydroxyl groups were modified to chloromethyl groups followed by conversion to onium salts, which are suitable as phase transfer catalysis. The catalytic activities of the supported catalysts were investigated in nucleophilic reactions of thiocyanate and cyanate ions with alkyl and aryl halides. The rates of the reactions have been investigated under different factors such as the nature and structure of the support, the amount of catalyst, the solvent, and the temperature.
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