Crystallization of Poly(ethylene adipate) within γ-Phase Poly(vinylidene fluoride) Matrix

The effects of PEA on the γ-phase PVDF crystal structure and the crystallization of PEA within the pre-existing γ-phase PVDF spherulites have been investigated by optical microscopy(OM), infrared spectroscopy(IR) and scanning electron microscopy(SEM). The results demonstrate that the γ-phase PVDF spherulites consist of the lamellae exhibiting a highly curved scroll-like morphology and develop preferentially in PEA-rich blend. With increasing PEA concentration, the scroll diameter increases and the scrolls are better separated from each other. PEA crystallizes first in the interspherulitic region and transcrystalline layer develops. Subsequently, the transcrystalline layer of PEA continues to grow within the γ-phase PVDF spherulites, e.g., in the region between the scrolls, until impinging on other PEA transcrystalline layers or spherulites. The crystallization kinetics results indicate that the growth rate of PEA crystals in the intraspherulitic region of γ-phase PVDF shows a positive correlation with content of PEA, but a negative one with the crystallization temperature of γ-phase PVDF.     

TDPAC and first-principles study of electronic and structural properties of a Pd-vacancy complex in undoped germanium

Pd is one of the metals suitable for inducing low-temperature crystallization in Ge. However, it is not clear how residual Pd atoms are integrated into the Ge lattice. Therefore, time-differential γ–γ perturbed angular correlations (TDPAC) technique using the ¹⁰⁰Pd(→¹⁰⁰Rh) nuclear probe produced by recoil implantation has been applied to study the hyperfine interactions of this probe in single-crystalline undoped Ge. A Pd-vacancy complex aligned along the <111> crystallographic direction with a unique interaction frequency of 8.4(5) Mrad/s has been identified. This complex was measured to have a maximum relative fraction of about 76(4)% following annealing at 350 ^°C. Further annealing at higher temperatures reduced this fraction, possibly via dissociation of the complex. Calculations suggest dissociation energy of 1.94(5) eV for the complex. DFT calculations performed in this work are in reasonable good agreement with the experimental values for the electric-field gradient of the defect complex in Ge and Si for comparison. The calculations predict a split-vacancy configuration with the Pd on a bond-centred interstitial site having a nearest-neighbour semi-vacancy on both sides (V-Pd_BI-V) in Ge and Si.     

Iodine(III)‐Catalyzed Rearrangements of Imides: A Versatile Route to α,α‐Dialkylated α‐Hydroxy Carboxylamides

A tertiary hydroxy group α to a carboxyl moiety comprises a key structural motif in many bioactive substances. With the herein presented metal‐free rearrangement of imides triggered by hypervalent λ³‐iodane, an easy and selective way to gain access to such a compound class, namely α,α‐disubstituted‐α‐hydroxy carboxylamides, was established. Their additional methylene bromide side chain constitutes a useful handle for rapid diversification, as demonstrated by a series of further functionalizations. Moreover, the in situ formation of an iodine(III) species under the reaction conditions was proven. Our findings clearly corroborate that hypervalent λ³‐benziodoxolones are involved in these organocatalytic reactions.     

Modification of Polylactide Nonwovens with Carbon Nanotubes and Ladder Poly(silsesquioxane)

Electrospun nonwovens of poly(L-lactide) (PLLA) modified with multiwall carbon nanotubes (MWCNT) and linear ladder-like poly(silsesquioxane) with methoxycarbonyl side groups (LPSQ-COOMe) were obtained. MWCNT and LPSQ-COOMe were added to the polymer solution before the electrospinning. In addition, nonwovens of PLLA grafted to modified MWCNT were electrospun. All modified nonwovens exhibited higher tensile strength than the neat PLA nonwoven. The addition of 10 wt.% of LPSQ-COOMe and 0.1 wt.% of MWCNT to PLLA increased the tensile strength of the nonwovens 2.4 times, improving also the elongation at the maximum stress.     

Metabolomics techniques applied in the investigation of phenolic acids from the agro-industrial by-product of Carapa guianensis Aubl

Processing of Carapa guianensis seeds to obtain oil on an industrial scale generates a significant amount of by-product, approximately 66% w/w, which is called cake and is a potential source of biomolecules, including simple phenolic structures. For this reason, studies were carried out on the chemical profiles of hydrolyzed extract from this agro-industrial by-product through High Performance Thin-Layer Chromatography (HPTLC) and Gas Chromatography coupled to Mass Spectrometry (GC–MS). These techniques were used to detect metabolic classes and/or groups, and to identify, for the first time, thirteen simple phenolic acids in this by-product. The sample antioxidant capacity was determined by methods of 2,2-diphenyl-1-picrylhydrazyl (DPPH)and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS⁺) radicals direct sequestration. The hydrolyzed fraction showed a total of 63.47% in the relative abundance of the total of compounds, standing out: p-hydroxybenzoic acid (39.19%) and protocatechuic acid (3,4-dihydroxybenzoic acid) (5.62%), both from hydroxybenzoic acids and 3-(3,4-dihydroxyphenyl)lactic acid, (7.76%) hydroxycinnamic acids derivatives. In these results, the fraction rich in simple phenolic acids was obtained, attributing the prominent behavior of this matrix antioxidant activity, expressed by (IC₅₀: of 16.42 µg/mL and 6.52 µg/mL for DPPH and ABTS⁺ radicals, respectively). The research demonstrated an alternative to applicability that involves sustainability from agro-industrial. These techniques were used to detect metabolic classes and/or groups, and to identify, for the first time, thirteen simple phenolic acids in this by-product, generating a process capable of converting biomass into a bioproduct, consisting of bioactive compounds, in addition to adding value to the industrial chain.     

A simple,rapid and sensitive method based on modified multiwalled carbon nanotube for preconcentration and determination of lead ions in aqueous media in natural pHs

In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL^?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples.     

Microwave‐assisted polycondensation of 4‐octylaniline with dibromoarylene

The Pd‐catalyzed polycondensation of 4‐octylaniline with various dibromoarylenes was carried out under microwave heating. Microwave heating led to a decrease in the reaction time and an increase in the molecular weight of the polymers as compared to conventional heating. Microwave heating also allowed the catalyst loading to be reduced to 1 mol %, yielding polymerization results that were comparable to those under conventional heating and 5 mol % catalyst. Investigations regarding field‐effect transistors and organic photovoltaic cells using the obtained poly(arylamine) with azobenzene units revealed that increasing the molecular weight of the polymer led to improved device performance, including hole mobility and power conversion efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 536–542     

Synthesis of diisocyanides with phenolic groups and their polymerization to helically chiral poly(quinoxaline‐2,3‐diyl)s

The development of synthetic routes which lead to five new diisocyanide monomers with one or two phenolic groups is described. Their polymerization behavior is studied with Pd‐ and Ni‐based initiators, as well as under microwave irradiation. The polymerizability is mainly dominated by steric effects as is concluded from experiments using different protecting groups. Chiroptical properties of these new polymers are studied by CD‐spectroscopy. After deprotection, helically chiral poly(quinoxalin‐2,3‐diyl)s are obtained which display a Brønsted function attached to a stereolabile biaryl axis whose configuration should be influenced by the chiral polymer backbone. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1320–1329     

Highly dispersed palladium nanoclusters incorporated in amino‐functionalized silica spheres for the selective hydrogenation of succinic acid to γ‐butyrolactone

Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO₂‐NH₂) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO₂‐NH₂ catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO₂‐NH₂ catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.