Palladium complexes bearing an N‐heterocyclic carbene–sulfonamide ligand for cooligomerization of ethylene and polar monomers

Herein, we report the synthesis of palladium complexes bearing an N‐heterocyclic carbene (NHC)‐sulfonamide bidentate ligand and their application in ethylene oligomerization and ethylene/polar monomer cooligomerization. These catalysts could smoothly catalyze ethylene oligomerization and ethylene/methyl acrylate cooligomerization albeit the performance was lower compared to that of a NHC–phenoxide catalyst. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 474–477     

Radical polymerization in the presence of peroxide and reducing agent monomer for branched polymers

In this article, we report the radical polymerization in the presence of peroxide and commercially available or designed reducing agent monomer (RAM) for the preparation of branched poly(methyl methacrylate)s (PMMAs). The reaction behavior of the RAM was studied by NMR. Triple‐detection SEC (TD‐SEC) analysis was used to confirm the branching structure of the prepared PMMAs and to investigate the influence of peroxide concentration and RAM concentration on molecular weight and branched structure. The obtained branched PMMAs exhibited high molecular weights and relatively narrow polydispersities at high conversion of MMA. Interestingly, a significant increase in molecular weight and degree of branching of the obtained polymers are observed in higher BPO concentration, these results are quite different from that reported in the literature. The unique radical polymerization mechanism in the RAM/BPO redox‐initiated radical polymerization system resulted in branched PMMAs with high molecular weights at relatively high RAM and BPO concentrations. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 833–840     

Full physicochemical characterization of malic acid: Emphasis in the potential as food ingredient and application in pectin gels

Malic acid, a carboxylic acid most found in fruits, is a smooth taste substance used as flavoring and preservative agent in foods, although not as used as citric acid. There are no studies focusing in quantitative results or investigations on its physicochemical properties, useful to the food industry, or even the confirmation of its calcium chelating, buffer texturizer and antioxidant alleged properties. Thus, the aim of this work was the assessment of most physicochemical properties of malic acid, solid and in solution, that could be useful to the food industry understand its real potential. The following analyses were carried out: melting point; structure (NMR, XRD, FTIR and SEM/EDS); TGA/DTG; solubility, hygroscopicity; antioxidant activity, iron chelating and antibacterial activities and stability of pectin gels. The melting temperature found was 129.71 °C. TGA/DTG exhibited first loss of mass around 140 °C. In the temperature range of 10 to 55 °C, it exhibited a high solubility in water, from 48.12 to 61.49 (100w), respectively. The tested bacteria, related to food spoilage, were inhibited by DL-malic acid 10% or higher. Chelating and antioxidant activities showed expressive results even in 1% solution. Pectin gels with malic acid had stronger structure and less syneresis than citric acid gels. In addition, calcium chelating, buffer texturizer and antioxidant properties were confirmed. Thus, malic acid has potential to be applied in a wide variety of food products as fortified beverages, frozen and refrigerated items, oils, pectin gels, hard and soft candies, and biofilms, due to all the characteristics quantified.     

Rational design of methacrylate monomers containing oxadiazole moieties for single‐layer organic light emitting devices

Methacrylate derived monomers functionalized with pendant oxadiazole moieties were synthesized and copolymerized with carbazole containing monomers to form polymers with electron and hole transporting fragments in the same molecule. Substituents on the oxidazole moiety were varied with the purpose of bandgap tuning and performance optimization when employed in single‐layer organic light emitting devices (OLED). Quantum mechanical calculations of the HOMO‐LUMO levels of the oxidazole derivatives were used to down‐select promising candidates for chemical synthesis and testing in single‐layer OLEDs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1663–1673     

Synthesis of New Poly(biphenylene oxide) with Pendent Trifluoromethyl Group

A new AB type of monomer 4′-fluoro-3,5-dimethyl-3′-trifluoromethyl-biphenyl-4-ol has been synthesized that leads to a new poly(arylene ether) by self polycondensation reaction. The monomer and the polymer have been well characterized by elemental analyses, FT-IR and NMR spectroscopy. Both FT-IR and NMR spectra of the polymers did not show any terminal phenoxy group indicating high conversion. The polymer showed glass transition at 278°C and very good thermal stability in synthetic air. GPC results indicate high molar mass development; Mw = 53200 and MWD = 2.29.     

Catalytic activity of chiral chelating N-heterocyclic carbene palladium complexes towards asymmetric allylic alkylation

Abstract

The catalytic activity of a series of chiral heteroaryl coordinated chelating N-heterocyclic carbene (NHC) palladium complexes towards asymmetric allylic alkylation (AAA) were presented here. The effects of different N-substituents, NHC backbones and chelate rings on the catalytic activity and the enantioselectivity of the alkylation of (E)-1,3-diarylallyl acetates with dialkyl malonate were investigated. The results showed that, under the optimized conditions, complexes 3a, 3b, and 3i carrying the pyridinyl-coordinated five-membered chelate ring showed high catalytic activity and chiral induction efficiency. The corresponding alkylated products were obtained in high yields with moderate ee. Furthermore, it was found that the substituents of (E)-1,3-diarylallyl acetates and the type of the nucleophile affect the results as well.     

Synthesis,Antimicrobial Activity and Semi-conducting Properties of Novel 2-(4-Chloro-1-Naphtyloxy)-2-Oxoethyl Methacrylate with 2-(Diethylamino)Ethyl Methacrylate Copolymers

The free-radical initiated copolymerization of 2-(4-chloro-1-naphtyloxy)-2-oxoethyl methacrylate (ClNOEMA) with 2-(diethylamino) ethyl methacrylate (DEAEMA) was carried out in 1,4-dioxane solution at 70 ± 1°C using 2,2′-azobisisobutyronitrile (AIBN) as an initiator with different monomer-to-monomer ratios (ranging from 0.15 to 0.85) in the feed. The copolymer composition obtained by elemental analysis led to the determination of reactivity ratios employing Fineman-Ross (F-R) and Kelen-Tüdös (KT) linearization methods. These parameters were also estimated using a non-linear computational fitting procedure, known as reactivity ratios error in variable model (RREVM). The prepared homo and copolymers were tested for their antimicrobial activity against bacteria and yeast. These copolymers have been converted into novel salts by reaction with the iodemethane (CH₃I). The copolymers and the corresponding salts have been characterized fully by a range of spectroscopic analysis techniques. The electrical conductivity dependence of temperature of the polymers were measured and the polymers exhibit the semi-conducting behavior, confirming that the electrical conductivity increases with increasing temperature. The poly(CINOEMA-co-DEAEMA) polymer doped by CH₃I for 15 min shows the highest conductivity. The optical band gap, activation energy and room temperature conductivity values of these polymers were obtained. These electronic parameters suggest that the poly(CINOEMA-co-DEAEMA)s doped by CH₃I for 15 min is an organic semiconductor with the thermally activated conduction mechanism.     

Design,Synthesis, and Properties of Substituted Polyacetylenes

This article reviews recent topics on the polymerization of substituted acetylenes, focusing on the synthesis of poly(diphenylacetylenes) and the living polymerization of phenylacetylenes. Diphenylacetylene (DPA) polymerizes with TaCl_s-n-Bu₄Sn to give a polymer which is thermally very stable but insoluble in any solvents. DPAs with various groups (e.g.,p-Me₃Si,m-Me₃Ge, p-t-Bu,and_p-PhO) polymerize similarly. These polymers are soluble and their M¯_w's reach 1 × 10⁶ to 3 × 10⁶. Some of them are more gas-permeable than poly(dimethylsiloxane). Several acetylenes (e.g., ClC -n-C₆H₁₃ and HCUC-t-Bu) have been found to undergo living polymerization with MoOCl₄-n-Bu₄Sn-EtOH. Whereas phenylacetylene (PA) does not polymerize in a living fashion, ortho-substituents in PA more or less suppress termination and chain transfer. PAs with bulky ortho groups (e.g., CF₃ and Me₃Ge) especially undergo virtually ideal living polymerization.