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Abstract: An efficient procedure for the synthesis of some N-nitroaryl derivatives of nucleobases via microwave-assisted N-nitroarylation of nucleobases in the presence of Si[O.sub.2] and [Cs.sub.2]C[O.sub.3] in DMSO, as the homogenizing [...]

Homo‐ and copolymerization of 1‐hexene (H) and 1,7‐octadiene (O) were done using two different catalysts 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediiminedibromo nickel (II) and rac‐ethylenebis(indenyl)zirconium dichloride [rac‐Et(Ind)2ZrCl2]. The metallocene catalyst showed higher activity than the nickel α‐diimine catalyst in homo‐ and copolymerization. The 1H NMR studies confirmed the formation of copolymers containing 8–47% of 1,7‐octadiene. In the copolymerization of hexene and diene, as the amount of incorporated diene in the copolymers increased, their Tg increased. TGA results showed that thermal stability of the polymer increases with the increase of 1‐hexene incorporation in the polymer chain. Finally 1‐hexene/1,7‐octadiene copolymers were functionalized by triethoxysilane in the presence of hexachloroplatinic acid. The 1H NMR spectrum of the functionalized samples showed that the double bonds in the copolymer structure were completely eliminated. The DSC analysis showed higher Tgs for the functionalized copolymer. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48934. [ABSTRACT FROM AUTHOR]

ABSTRACT Limited amount of isotactic polypropylene (iPP) is added to high-density polyethylene (HDPE) containing 1% w/w an oxo-biodegradable additive and extruded and converted to films. The films are put under UV irradiation for different periods of time. Irradiation of the films for 6 weeks imposes remarkable effects on viscosity average molecular weight ( Mv) and carbonyl index (CI) of them. Mv decreases from 3.4 × 105 to 4.7 × 104 g mol−1 for neat HDPE films; from 3.1 × 105 to 3.3 × 104 g mol−1 for the films containing oxo compound, and from 1.5 × 105 to 2.6 × 104 g mol−1 for the films containing oxo compound and 1% w/w iPP. Carbonyl index of the neat HDPE films increases from 4 to 8.7 while for the sample containing only the oxo compound it increases from 4.5 to 7.3 and for the sample containing both oxo compound and iPP it decreases from 12.0 to 8.8. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicate more cracks and uniform degradation in the samples containing iPP and oxo compound. Thermogravimetric analysis (TGA/DTG) of the samples shows that the samples containing iPP and oxo compound have lower decomposition temperature after UV irradiation. Finally, it can be said that the presence of iPP in HDPE matrix containing oxo compound can improve HDPE oxo-biodegradablity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45843. [ABSTRACT FROM AUTHOR]

Polyethylene reactor alloys are synthesized through heterogeneous ethylene polymerization with a new type of Ziegler-Natta (ZN)/late transition metal (LTM) hybrid catalyst. The effect of various parameters including catalyst composition (LTM/ZN = 0.01, 0.02, 0.04), polymerization temperature (TP = 30, 30-60, 60 °C) and loading temperature (TL = 30, 60 °C) on catalyst activity, chain's vinyl content, viscosity average molecular weight ( Mv) and thermal properties are investigated. Two distinct melting peaks were observed in the ranges of 110-140 °C and 60-90 °C, indicating presence of two different lamellar structures. LTM/ZN ratio shifted melting peaks toward lower values. Rheological properties confirmed homogeneity of polymer blend's microstructure as they follow time temperature superposition. [ABSTRACT FROM AUTHOR]

In this study, the copolymerization of ethylene with nonconjugated diene (5-ethylidene-2-norbornene) was carried out with a bis(2-PhInd) ZrCl2 metallocene catalyst. Some polymerization factors that were considered affective on the catalyst activity, including comonomer content in the feed, ethylene pressure, and polymerization temperature, were investigated via response surface methodology to determine the optimum polymerization conditions. We found that the comonomer content in the feedstock had no enormous effect on the catalyst activity depression. Also, the polymerization temperature increment through the scrutinized range decreased the copolymerization activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Various elastomeric polypropylenes (PPs) are synthesized through homogeneous propylene polymerization with metallocene catalyst (2-PhInd)2ZrCl2 in the presence of different cocatalyst mixtures: triethylaluminum (TEA)/methylaluminoxane (MAO) or triisobutylaluminum (TIBA)/MAO in the range of AlAlR3/AlMAO = 0.0-0.9. The cocatalyst formulation impacts the resultant polymer microstructure and the thermal and dynamic mechanical properties of the produced PPs. 13C NMR analysis of the polymers reveals essentially atactic PP, with mmmm = 7.9% , when AlAlR3/AlMAO = 0.0. The mmmm pentad content is maximized when AlAlR3/AlMAO = 0.8; for TIBA, mmmm = 23.5%; and for TEA, mmmm = 17.6%. Differential scanning calorimetry analysis and dynamic mechanical thermal analysis corroborate these findings. Specifically, Tm, Δ Hm, and Tg are essentially maximized under these conditions, and the minimum damping is observed for AlAlR3/AlMAO = 0.6-0.8. 1H NMR analysis of the mixtures of catalyst and cocatalysts (without monomer) shows very minor differences for [Zr]:AlAlR3 in the range of 1:1-1:5. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

The effect of adding various aluminum alkyls (R = Et, i-Bu) on the polymerization of propylene is studied using a (2-PhInd)2ZrCl2 pre-catalyst. A mild deactivating effect is found upon addition of TIBA, whereas TEA shows a sharp deactivating effect. Increasing amounts of AlR3 results in a significant activity increase for TIBA, but an activity plateau for TEA. AlR3 imposes remarkably different effects on the molecular weight and stereochemical microstructure of polymers. As the TIBA concentration increases, $\overline {M} _{{\rm v}} $ increases at first, growing from 49 000 to 72 000, but subsequently drops to 40 000. For TEA, $\overline {M} _{{\rm v}} $ decreases sharply, plummeting from 49 000 to 17 000. Both TIBA and TEA increase the mmmm pentad content from 7.9 to 23.5% and 17.6%, respectively. [ABSTRACT FROM AUTHOR]

A very simple and efficient solvent-free method for the direct conversion of carboxylic acids to primary, secondary, tertiary alkyl, and aromatic amides in the presence of the corresponding ammonium salts, silica-supported 2,4,6-trichloro-1,3,5-triazine, and triethylamine is described. The reactions proceed rapidly at room temperature, and the products are obtained in moderate to excellent yields. [ABSTRACT FROM AUTHOR]

Abstract: This note shows that some of the results, interpretations and discussions presented by Dong et al. [X. Dong, L. Wang, J. Zhou, H. Yu, T. Sun, Catalysis Communications 7 (2006) 1–5] may not be correct. Here by comparing the internal diameter of beta-cyclodextrin pore and the external diameter of MCM-41 particles it is shown that a single MCM-41 particle can not be located in the pore of beta-cyclodextrin and even it can be concluded that beta-cyclodextrin may be located in the pores of MCM-41 and therefore the interpretations presented in the article mentioned above are not correct. Even more the Scheme presented in the said article is incorrect and a better demonstration of the facts is proposed here. [Copyright &y& Elsevier]