Summary: Graphite nanosheet (GNS) was prepared by physical/chemical method. The polyaniline (PANI)/graphite nanocomposites were synthesized by in situ polymerization of aniline monomer using different amounts (1 to 5 wt%) of graphite nanosheets. The formation of graphite nanosheets was confirmed by Transmission Electron Microscope (TEM) and X-ray Diffraction (XRD). The surface morphology of exfoliated graphite and PANI/GNS nanocomposites were studied by the Scanning Electronic Microscopy (SEM). A device for electrical conductivity measurements was developed in this work and the results show that the conductivity of PANI/GNS is dependent of the GNS contents.

Nanofillers of polyaniline nanofibers (PANI) with graphite oxide (GO) or reduced graphite oxide (rGO) were synthesized and characterized. Four samples of PANI/graphite with 10% and 30% of GO or rGO were obtained. The addition of GO or rGO in PANI nanofibers increased the conductivity and improved the thermal stability of the nanofillers. These nanofillers were used in the in situ ethylene polymerization producing PE/PANI/graphite nanocomposites characterized by SEM and TEM, revealing very particular morphologies. PANI/GO or PANI/rGO nanoparticles showed a good dispersion in polyethylene, and an increase in the thermal stability of the final material was observed. POLYM. COMPOS., 39:3645–3655, 2018. © 2017 Society of Plastics Engineers

a b s t r a c tTwo new complexes of Ti and Zr were synthesized with 3-hydroxyflavone bidentate ligand and investigated in homogeneous ethylene polymerization. Both complexes were characterized by UV-VIS, 1 H and 13 C NMR, and electrochemical studies. The geometries and energies of all possible isomeric species were studied by full unconstrained optimizations performed at Density Functional Theory (DFT) level. The polymerization reactions were performed at different experimental conditions with methylaluminoxane (MAO), as the cocatalyst. Both complexes were active in ethylene polymerization in all the conditions used. However, zirconium complex showed the best activity comparing to the titanium complex at 2500 Al/M ratio. The polymers obtained were high density polyethylene with ultra high molecular weights.

A new titanium catalyst easily synthesized from ethylmaltol bidentate chelator ligand was studied in homogeneous and heterogeneous ethylene polymerization. The dichlorobis(3-hydroxy-2-ethyl-4-pyrone)titanium(IV) complex was characterized by 1 H and 13 C NMR (nuclear magnetic resonance), UV-Vis and elemental analysis. Theoretical study by density functional theory (DFT) showed that the complex chlorines exhibit cis configuration, which is important for the activity in olefin polymerization. The complex was supported by two methods, direct impregnation or methylaluminoxane (MAO) pre-treatment, in five mesoporous supports: MCM-41 (micro and nano), SBA-15 and also the corresponding modified Al species. All the catalytic systems were active in ethylene polymerization and the catalytic activity was strongly influenced by the method of immobilization of the catalyst and the type of support. Keywords: catalysis, synthesis, mesoporous support, immobilization, polyethylene IntroductionPolyethylene (PE) has a broad application in different segments of the everyday life, from food packaging to resistant pieces for engineering. Due to the polymer industrial demands, continuous development of new technologies and synthetic methods for obtaining this material are necessary. Existing processes, involving polyethylene synthesis in industrial and/or research scale, use Ziegler-Natta, metallocene, and more recently, postmetallocene catalysts. Our research group has studied the synthesis of different post-metallocene catalysts and tested these complexes in ethylene polymerization. Organometallic complexes of Ti and Zr were obtained from bidentate chelator ligands as naphthoquinone, methylpyrone, ethylpyrone and 3-hydroxyflavone. [1][2][3][4][5] All the synthesized complexes were active in homogeneous ethylene polymerization at different reaction conditions. 3-Hydroxy-2-methyl-4-pyrone (methylpyrone or maltol) is a non-toxic compound of natural occurrence in many plants, 6 while 3-hydroxy-2-ethyl-4-pyrone (ethylmaltol) is a synthetic commercial product. These organic compounds are commonly used in food industries as flavor ingredients. Both hydroxypyrones are characterized by their synthetic versatility and they easily coordinate with transition metals of group IV to give L 2 MCl 2 complexes.7 Bis(maltolate) metal(IV) complexes are extensively used in medical studies to assess their therapeutic value as active agents against diabetes, as agents for controlling metal levels in the body and as contrast agents in imaging applications. [8][9][10][11][12] Maltolate complexes appear attractive to catalyze olefin polymerization reaction as well. In 2001, Sobota et al. 13 synthesized and characterized titanium complexes of methylmaltol and verified their catalytic activity in ethylene and propylene polymerization. Subsequently, our research group has synthesized several Ti and Zr complexes Gheno et al. 2083 Vol. 27, No. 11, 2016 analogous based in maltolate ligands. The synthesized complexes were shown to be active in the ethylene...

Este artigo mostra a síntese e caracterização do ligante isopropilmaltol obtido a partir do furfural e também um novo complexo diclorobis-(3-hidroxi-2-isopropil-4-pirona)titânio(IV) com estrutura cis. Dados de ressonância magnética nuclear de 1 H, análise elementar e UV-Vis confirmam a formação do complexo. Este complexo foi estudado em reações de polimerização de etileno utilizando metilaluminoxano (MAO) como co-catalisador. A atividade catalítica deste complexo é baixa, entretanto foram obtidos polietilenos com alto peso molecular que são interessantes para diferentes aplicações.This report describes a new synthesis of isopropylmaltol from furfural. This organic compound was used as ligand to obtain a new complex, the dichlorobis-(3-hydroxy-2-isopropyl-4-pyrone) titanium(IV). 1 H nuclear magnetic ressonance, elemental analysis and UV-Vis analysis confirm the complex formation. This complex was investigated in ethylene polymerization using methylaluminoxane (MAO) as cocatalyst. The catalytic activity was low, however, there were obtained very high molecular weight polyethylenes, which are interesting for various special applications.