Graft copolymerization of styrene onto deproteinized natural rubber (DPNR) using tert-butyl hydroperoxide (TBHPO) and tetraethylene pentamine (TEPA) as redox initiator have been investigated. The effects of initiator and monomer concentration on conversion and grafting efficiency were studied. The dynamic mechanical and thermal properties of the graft copolymer were investigated over the wide range of temperatures. It is shown that a high value of storage modulus for the graft copolymer, which was about 25 times as high as that of DPNR, was achieved. The graft copolymer (DPNR-graft -PS) showed the outstanding tensile strength and stable thermal properties. These enhancements were attributed to the interaction between NR and polystyrene as a result of the graft copolymerization. Morphology observation by transmission electron micrograph (TEM) revealed that the core-shell arrangement of the DPNR-graft -PS with about 30 nm in thickness of polystyrene nano-layer was achieved.

Duas soluções à base de água contendo precursores do óxido YBa2Cu3O7-x e utilizando edta (ácido etilenodiaminotetra-acético) como agente complexante são apresentadas. Estes precursores foram usados na deposição de camadas finas de materiais supercondutores de altas temperaturas (HTSC). A influência do comportamento da complexação na formação de soluções e de géis transparentes e homogêneos após a combinação de acetatos de metais e outros modificadores foi estudada, comparada e interpretada utilizando equilíbrios metal-ligante. A ocorrência de diferentes espécies químicas em diferentes valores de pH pode estar relacionada às condições de formação de géis estáveis. Os precursores foram utilizados na deposição de filmes finos supercondutores texturizados por dip coating. A análise por difratometria de raios X de pó (XRD) indicou que uma única fase YBCO (óxido de ítrio, bário e cobre) foi obtida. A técnica de espectroscopia no infravermelho por refletância total atenuada (ATR-FTIR) foi utilizada para determinar o nível de carbono residual nos materiais YBCO finais, que foi menor do que 0,01%.

Two water-based YBa2Cu3O7-x precursor solutions using edta (ethylenediaminetetraacetic acid) as complexing agent are presented. These precursors were employed to deposit thin layers of high-temperature superconducting (HTSC) materials. The influence of the complexation behavior on the formation of transparent and homogeneous solutions and gels after the combination of metal acetates and other modifiers was studied, compared and interpreted using metal-ligand equilibria. The occurrence of different chemical species at different pH values appears to be related to stable gel formation conditions. It is found that both acetic acid and edta play an important role in controlling the condensation reaction to form a continuous network polymer. The precursors were used to deposit textured superconducting thin films on SrTiO3 (STO) substrates by dip coating. Analysis by X-ray diffractometry (XRD) indicated that a single YBCO (yttrium barium copper oxide) phase was obtained. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to determine the carbon residue level in the YBCO final materials, which was lower than 0.01%.