Low Degree Of Branching Research Articles

Studying the Characteristics of a Waste Industrial Со-Мо/Al2O3 Catalyst for the Deep Hydrotreatment of Diesel Fuel

The physicochemical properties of a waste industrial Со-Мо/Al2O3 catalyst for the deep hydrotreating of diesel fuel are studied. IR spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA), and scanning electron microscopy (SEM) are used to establish that the catalyst surface is uniformly coated with a coke film. This soft coke is mostly a mixture of saturated hydrocarbons with a low degree of branching in their structure. The coke is oxidized at temperatures of 190–375°C (soft coke) and 375–525°C (hard coke); its quantitative removal is achieved by means of oxidative calcination in air for 3 h at 550°C. X-ray diffraction, scanning electron microscopy, low-temperature nitrogen adsorption, and chemical analysis are used to show that the waste catalyst undergoes considerable structural transformation with a 7.7% drop in the Mo content and the accumulation of Fe, Ha, and V impurities. As a result of sintering, its specific surface area and total pore volume are reduced by 31.5 and 28.4%, respectively. The obtained data are needed to develop a scheme for its recycling.

Unmasking the heterogeneity of carbohydrates in heartwood, sapwood, and bark of Eucalyptus

In this study, the cellulose and hemicelluloses in heartwood, sapwood, and bark of E. urophylla × E. grandis were comprehensively investigated. The ultrastructural topochemistry of carbohydrates in cell walls was examined in situ by confocal Raman microscopy. Cellulose and alkali-extractable hemicelluloses samples were isolated from different tissues and comparatively characterized by compositional carbohydrate analyses, determination of molecular weights, FT-IR spectroscopy, and XRD and NMR techniques. It was found that among all of the samples, heartwood cellulose had the highest molecular weight as well as the lowest degree of crystallinity. Meanwhile the hemicelluloses in heartwood had higher xylose content, lower degree of branching, slightly lower molecular weights but narrower polydispersity than those in sapwood. The eucalyptus hemicelluloses mainly consisted of (1→4)-β-D-xylan backbone with glucuronic acid side chains. Furthermore, the hemicelluloses isolated from sapwood had a higher degree of substitution with terminal galactose than those isolated from heartwood and bark.

Pentafluorophenyl Groups as Remote Substituents in Ni(II) Polymerization Catalysis

Perfluoroaromatic molecules have been studied intensively as versatile electron-poor π systems. We demonstrate the use of pentafluorophenyl substituents in remote positions of Ni(II) salicylaldiminato catalysts for ethylene polymerization. With their strongly electron-withdrawing character, high molecular weights of Mn > 105 g/mol and simultaneously low degrees of branching are accessible due to an efficient suppression of β-hydride elimination. This can be ascribed to suppressed nickel–aryl interactions and reduced electron densities at the metal center, as concluded from X-ray crystal structure analysis and electrochemical studies. The pentafluorophenyl-substituted catalyst is stable under aqueous conditions for direct polymerization to dispersions of well-defined nanocrystals.

Relationship between heat treatment on structural properties and antitumor activity of the cold-water soluble polysaccharides from Grifola frondosa.

Grifola frondosa is a basidiomycete fungus with potential biomedical applications owing to the presence of bioactive polysaccharides. The activities of polysaccharides are influenced by many factors, particularly temperature; however, the optimal temperature and conditions for preparation of polysaccharides from this organism have not yet been determined. Therefore, in this study, cold-water soluble polysaccharides from Grifola frondosa were extracted at 4 °C (GFP-4) and purified. GFP-4-30, GFP-4-60 and GFP-4-90 were obtained from GFP-4 after treatment at 30 °C, 60 °C, or 90 °C, respectively, for 6 h. MTT results showed that GFP-4 had the highest inhibitory effects on the proliferation of SPC-A-1 cells in vitro. High-performance gel permeation chromatography results demonstrated that the molecular weight of GFP-4 was 1.05 × 106 Da and that GFP-4-30, GFP-4-60, and GFP-4-90 showed different levels of degradation and generated small molecule sugars. Fourier transform infrared spectroscopy, gas chromatography, and nuclear magnetic resonance results indicated that GFPs mainly consisted of α-D-Galp, α-D-Manp and α-D-Glcp. Periodate oxidation, Smith degradation, and methylation results showed that the backbones of the molecules consisted of 1,3-linked-Galp. After heat treatment, percentages of (1 → 3,4) α-D-Galp in heat-treated polysaccharides were obviously decreased, indicating their lower branching degree, and resulting in weaker antitumor effects. Overall, our findings demonstrated changes in the structure-activity relationships of GFP-4 after heat treatment and provided a theoretical basis for the application of GFP-4 in the food and drug industries.

Ultrasound-assisted extraction of pectin from artichoke by-products. An artificial neural network approach to pectin characterisation

Artichoke (Cynara scolymus L.) by-products can be used as a good source of pectin. The aim of this work was to compare different pectin extraction methods: power ultrasound (US), enzymes, combination of US and enzymes (US + E), and acids (nitric and sodium citrate). After 6 h, pectin yield was higher when US was applied in combination with Celluclast®1.5 L (up to 13.9%). Structural characterisation showed that US-extracted pectins had lower weight-average molecular weight (Mw) values (146–155 kDa) than pectin extracted with US + E (160–267 kDa) and acid-extracted pectin (329–352 kDa). Monomeric composition reflected that pectin extracted with acids had the highest galacturonic acid (GalA) contents (82.2–90.2%) and the lowest degree of branching [Rha/GalA] (0.026–0.031). Structural characteristics of the different pectins were modelled using two artificial neural networks (ANN) considering composition parameters (Model I) and pectin FT-IR spectra (Model II). In addition, a third ANN was built to determine differences and similarities in the GC-MS spectra of monomeric composition (identified and unidentified monosaccharides) (Model III) showing characteristic patterns with high accuracy rates (above 95% on the test set). Structural differences depending on the extraction method of pectin have been established and these models could be applied to pectin from other sources.

Characterizations of a pectin extracted from Premna microphylla turcz and its cold gelation with whey protein concentrate at different pHs

In this study, the physicochemical properties of an ammonium oxalate extraction pectin (AOP) from Premna microphylla turcz was investigated. Moreover, its cold gelation with undenatured whey protein concentrate (WPC) was studied at room temperature and different pHs. Characterizations of AOP demonstrated that AOP was a linear low-methoxyl pectin rich in homogalacturonan with low branching degree of RG-I, leading to its good gelling properties. Gelation between AOP and WPC was mainly investigated by turbidity measurement, FTIR, CLSM and ITC. The results showed that an optimal complex ratio for gelation was observed at 1:5 at pH 6.0. Moreover, AOP was the backbone of the composite gel and WPC might act as crosslinking agents through electrostatic or hydrophobic interaction at different pHs. When pH was around the pHΦ of the complex, composite gel was mainly constructed by electrostatic interaction. With the increase of pH, the electrostatic interaction between AOP and WPC gradually weakened, while the hydrophobic interaction constantly increased. When pH was higher than the pHc of the complex, composite gel was mainly formed by hydrophobic interaction. The results of this study are conducive to further utilization of Premna microphylla turcz pectin to develop related food products.

Investigating almond seed oil as potential biodiesel-based drilling mud

With increasing strict environmental laws, there is a need for operators to design a benign oil-based muds (OBMs). In this study, oil extracted from non-edible sweet almond seed (SASO) was used as the continuous phase to formulate biodiesel-based drilling mud (BBDM). Different properties of the BBDM including the economic viability were evaluated and compared with those of the diesel OBM to determine the applicability of these properties for drilling fluids and their level of toxicity to the environment. The results indicate that the rheology, filtration properties, electrical stability, thermal stability and shale swelling inhibition performance of the BBDM are comparable with those of the diesel OBM. The biodiesel has a significantly higher flash point of 169 °C than the diesel with 78 °C; demonstrating that it can supply better fire safety than the diesel. The data of the toxicity test indicate SASO to be safer and less harmful compared to diesel #2 type used. After the 28-day period of biodegradation tests, the BBDM and the diesel OBM showed 83% and 25.2% aerobic biodegradation with Penicillium sp., respectively. The low branching degree and absence of aromatic compounds in the BBDM contributes for its higher biodegradation. The economic evaluation of the BBDM indicates low cost of formulation and waste management. The general outcome of the tests illustrates that SASO has the potentials of being one of the technically and environmentally feasible substitutes for the diesel OBM.

Scale Inhibitor and Dispersant Based on Poly(Acrylic Acid) Obtained by Redox‐Initiated Polymerization

AbstractLow molar mass poly(acrylic acid) (PAA) is generally obtained by free radical polymerization of acrylic acid (AA) in aqueous solution, using thermal initiators and some chain transfer agent. However, under such conditions it is rather difficult to efficiently produce molar masses as low as those required for obtaining an effective dispersant. In this work, the semibatch polymerization of AA at 45 °C is considered, using potassium persulfate (KPS) and sodium metabisulfite (KPS/NaMBS), or alternatively KPS and sodium hypophosphite (KPS/NaHP) as redox initiators to produce PAA of controlled low molar masses. These initiation systems allow the production of PAA with Mn as low as 2.0 kDa, relatively narrow molar mass distribution (1.5 < Mw/Mn < 3.0), and low branching degree. Most of the investigated polymerizations reach almost complete conversions (>95%); and it is verified that both reductants, NaMBS and NaHP, also behave as chain transfer agents. Finally, the investigated process with redox couples allowed the production of PAA with acceptable dispersant and antiscaling properties.

Active site selectivity of 2,3-Bis[(2,6-diisopropylphenylimino)butane] nickel/MAO/ZnEt2 system toward ethylene polymerization for modulating polyethylene microstructure

2,3-Bis[(2,6-diisopropylphenylimino)butane] nickel/MAO system toward ethylene polymerization displays two active sites with ultraviolet absorption bands at 456 nm and 492 nm to produce branched polyethylenes, respectively. It is surprising that adding ZnEt2 results in selective catalyst active site to modulate polyethylene microstructure. 200 equiv. of ZnEt2 causes a more than 30% decrease of branching degree from 140 to 97. The UV,EPR and CV results suggest that the active site at 456 nm is easily reduced by ZnEt2. However, the active site at 492 nm still exhibits high catalytic activity, producing polyethylenes with a relatively low branching degree.

Cationic para-benzhydryl substituted α-diimine nickel catalyzed ethylene and 1-decene polymerizations via controllable chain-walking

A series of α-diimine nickel complexes bearing para-benzhydryl groups, {[(2,6-R2-4-CHPh2C6H2N = C)2Nap]NiBr2, Nap: 1,8-naphthdiyl, R = Me (C1); R = Et (C2); R = iPr (C3)}, were synthesized and characterized. Upon activation with AlEt2Cl, these para-benzhydryl substituted catalysts conducted the ethylene and 1-decene polymerizations via controlled chain-walking process. These nickel complexes exhibited good thermal stability and high activities (up to 106 g PE (mol Ni h)−1) towards ethylene polymerization, producing high molecular weight polyethylenes with a relatively low degree of branching and narrow polydispersities (Mw/Mn ≤ 2.01). The catalytic activities [(0.81–2.42) × 106 g PE (mol Ni·h)−1], polyethylene molecular weights [Mn: (7.9–29.3) × 104 g mol−1] and total branching densities (57–102/1000C) can be tuned over a wide range. These controlled branching degrees of the obtained polyethylenes were decreased with increasing the bulkiness of the ligand and decreasing the polymerization temperature. Polymerization of 1-decene using these cationic nickel complexes generated branched poly(1-decene)s (69–87/1000C) with high molecular weights and narrow polydispersities (Mw/Mn = 1.18–1.55).

Fine structure, crystalline and physicochemical properties of waxy corn starch treated by ultrasound irradiation

As a simple and effective physical method, ultrasound irradiation has been used to modify starch. Native waxy corn starch was treated by ultrasound irradiation at 100 and 400 W in this study. Compared with native waxy corn starch, lower proportion of B1, B2, and B3, higher proportion of A chain were observed in ultrasonicated waxy corn starch. 1H NMR combined with HPSEC-MALLS-RI data showed that lower degree of branching was observed in ultrasonicated waxy corn starch, and α-1,4 glycosidic linkages were more stable than α-1,6 glycosidic linkages in waxy corn starches. 13C NMR data indicated that the content of double helices was decreased, and single helix and amorphous components were increased after ultrasound irradiation. The A-type crystal structure was scarcely affected according to X-ray diffraction (XRD) analysis. The granule surface of ultrasonicated waxy corn starch became notch and rough fragment, and lower particle diameter was observed in ultrasonicated waxy corn starch. These results demonstrated that ultrasound irradiation affected chain length distribution, double helices, single helices and amorphous state, especially α-1,4 glycosidic linkages and α-1,6 glycosidic linkages, of waxy corn starch.

In vitro enzymatic hydrolysis of amylopectins from rice starches

The effects of the molecular structures of amylopectins on the enzymatic hydrolysis of waxy-rice amylopectin (WRA) and normal-rice amylopectin (NRA) were investigated. The results indicated that compared to NRA, WRA possessed larger chain length, number of chains, internal chain length, degree of polymerisation, interblock chain length, and lower degree of branching and short:long B-chains, which caused WRA was much less susceptible to enzymatic hydrolysis than NRA. The digestibility curves for WRA and NRA were well fitted by the first-order kinetic equation. WRA and NRA were hydrolyzed in two separates phases in the LOS plots. Whether using α-amylase alone, or together with amyloglucosidase, WRA and NRA exhibited different digestibility rates due to different chain structure of amylopectin. The low C1∞ values predicted that WRA and NRA would have little impact on blood glucose concentrations in the early digestion stage. HPLC results showed that G1∼G5 from WRA using α-amylase were lower than that from NRA, whereas from WRA were higher than that from NRA. There was the synergism between α-amylase and amyloglucosidase in glucose released from WRA and NRA.

Implications of recovery procedures on structural and rheological properties of schizophyllan produced from date syrup

This study investigates the effects of different recovery procedures on high molar mass schizophyllan produced by Schizophyllum commune using low value agricultural residues. Recovered extracellular polysaccharides (EPSs) were compared in terms of purity, sugar composition, degree of branching, molecular weight, and rheological properties. Performing different recovery methods, such as re-dissolving in water and re-precipitation with ethanol on produced EPS, provided schizophyllan with purity similar to the commercial grade. Besides, Freeze-thawing cycles allowed the fractionation of schizophyllan based on branching degree and solubility. The EPSs with higher purity and lower degree of branching (less conformational flexibility) showed higher viscosity. This study evidences the possibility of producing EPSs with excellent rheological properties using low value agricultural side products. Furthermore, our results demonstrate the importance of recovery methods for tailoring the purity, molecular structure and macroscopic properties of the produced polysaccharides for specific applications.

Combining control of branching and sulfonation in one-pot synthesis of random sulfonated polyarylethersulfones: effects on thermal stability and water retention

In functional polymers with tunable hydrophilic behaviour like sulfonated polyarylethersulfone (SPES) high ionic conductance can be obtained directly by increasing the concentration of sulfonic moieties along the macromolecular chain. This, however, often comes to the cost of excessive water sorption, which can lead to membrane rupture and consequent device failure. To overcome this drawback, and to reconcile high hydrophilicity with the high mechanical properties of aromatic polymers, we propose the use of SPES copolymers with a low degree of branching. A series of branched SPES was synthesized using homogeneous (one-pot) copolymerization by replacing an amount up to 0.9% mol of the difunctional monomer 4,4′-dihydroxydiphenyl with the trifunctional 1,3,5-trihydroxybenzene (THB). The polymers were characterized by 1H-NMR spectroscopy, intrinsic viscosity, water sorption measurements, thermogravimetric analysis and differential scanning calorimetry. Like linear SPES, branched SPES is totally amorphous and soluble in polar aprotic solvents, lending itself to easy fabrication of membranes and coatings. Besides reducing the water sorption and in-plane swelling of SPES membranes upon equilibration in liquid, branching also improves the retention of water in swollen membranes.

Variation in structure and properties of poly(glycerol adipate) via control of chain branching during enzymatic synthesis

Poly (glycerol adipate) (PGA) can be produced from divinyl adipate and unprotected glycerol by an enzymatic route to generate a polymer with relatively low molar mass (12 kDa). PGA bears a pendant hydroxyl group which imparts a hydrophilic character to this water insoluble polymer. We have examined the effect of synthesis temperature on polymer characteristics through various techniques including FT-IR, 1H and 13C NMR, surface and thermal analysis, both to expand the data already present in the literature about this material and to understand better its properties for potential pharmaceutical applications. The use of a lipase (Novozym 435) as a catalyst suppresses cross-linking at the pendant glyceryl hydroxyl through steric hindrance at the active site, thus producing polymers with low degrees of branching (5–30%), and removes the need for any pre- or post-polymerization protection/deprotection reactions. Careful temperature control during synthesis can give polymers with reproducible molecular weights and reduced amounts of polymer branching compared to synthesis at higher temperatures. Due to the ability of the synthetic route to produce a range of structures, PGA generated by enzymatic routes may emerge as a useful biodegradable polymer platform to engineer solid dispersions or nanoparticles for healthcare applications.

Native and structurally modified gum arabic: exploring the effect of the gum's microstructure in obtaining electroactive nanoparticles.

Electroactive nanoparticles combining gum arabic (GA) and polyaniline (PANI) were prepared by chemical synthesis. The gum consists of highly branched anionic polysaccharides with some protein content. GA was structurally modified by Smith controlled degradation, in order to reduce its degree of branching (GAD), aiming the elucidation of the relationship between the structure and the properties of complex polysaccharides. The modification was studied by SEC, GC-MS, (13)C NMR and colorimetric methods. GAD has lower molecular mass, lower degree of branching and lower uronic acid content. Besides it is enriched in galactose and protein when compared with GA. The obtained composites (GA-PANI and GAD-PANI) were thoroughly characterized. Although the use of both polysaccharides (GA and GAD) produced highly stable electroactive nanoparticles, the best combination of properties was achieved for GA-PANI. The sample GAD was not able to prevent the occurrence of crosslinking between PANI chains, possibly due to its lower microstructural complexity which diminishes the occurrence of hydrogen bonds between the polymers.

Different structures of heterogeneous starch granules from high-amylose rice.

High-amylose cereal starches usually have heterogeneous starch granules in morphological structure. In the present study, the polygonal, aggregate, elongated, and hollow starch granules were separated from different regions of the kernels of high-amylose rice, and their structures were investigated. The results showed that the polygonal starch granules had low amylose content and high short branch-chain and branching degree of amylopectin, and exhibited A-type crystallinity. The aggregate starch granules had high long branch-chain of amylopectin, relative crystallinity, and double helix content, and exhibited C-type crystallinity. The elongated starch granules had high amylose content and low branching degree of amylopectin and relative crystallinity, and exhibited C-type crystallinity. The hollow starch granules had very high amylose content, proportion of amorphous conformation, and amylose-lipid complex, and very low branch-chain of amylopectin, branching degree of amylopectin, and double helix content, and exhibited no crystallinity. The different structures of heterogeneous starch granules from high-amylose rice resulted in significantly different thermal properties.

Mineral oil in human tissues, Part II: Characterization of the accumulated hydrocarbons by comprehensive two-dimensional gas chromatography

Mineral oil hydrocarbons are by far the largest contaminant in the human body. Their composition differs from that in the mineral oils humans are exposed to, and varies also between different tissues of the same individual. Using the presently best technique for characterizing the composition of mineral oil hydrocarbons, comprehensive two-dimensional gas chromatography (GC×GC), the hydrocarbons in human tissues were compared to those of various mineral oils. This provided information about the strongly accumulated species and might give hints on the flow path through the human body. The selectivity of accumulation is probably also of interest for the risk assessment of synthetic hydrocarbons (polyolefins). GC×GC grouped the MOSH into classes of n-alkanes, paraffins with a low degree of branching, multibranched paraffins and naphthenes (alkylated cyclic hydrocarbons) with 1–4 rings. Metabolic elimination was observed for constituents of all these classes, but was selective within each class. The MOSH in the subcutaneous abdominal fat tissues and the mesenteric lymph nodes (MLN) had almost the same composition and included the distinct signals observed in mineral oil, though in reduced amounts relative to the cloud of unresolved hydrocarbons. The MOSH in the liver and the spleen were different from those in the MLN and fat tissue, but again with largely identical composition for a given individual. Virtually all constituents forming distinct signals were eliminated, leaving an unresolved residue of highly isomerized hydrocarbons.

Ruthenium(IV) Complexes for Ethylene Insertion Polymerization

The synthesis, characterization, and ethylene polymerization behavior of novel RuIV(η3:η3-C10H16)(OPO) (OPO = bis(arenesulfonato)phosphine) complexes is reported here. Upon activation with AlMe3-depleted methylaluminoxane (dMAO), the Ru(IV) precursors were able to produce polyethylene with activities up to 1182 h–1 turnover frequency (TOF). The polymers were highly linear with a low degree of branching (<12 methyl branches per 1000 C) and had high molecular weights (up to Mp = 289 kg mol–1) with a bimodal molecular weight distribution. The polymerization activity increased with decreasing donor strength of the OPO ligand.

Study on branching structure, melting, and crystallization of polyethylene prepared by nickel a-diimine catalyst covalently intercalated inside OapPOSS-modified laponite clay gallery

Ethylene polymerization was catalyzed by using nickel α-diimine covalently supported inside the octaaminopropyl polyhedral oligometric silsesquioxane (OapPOSS)-modified Laponite clay layers. The branching structure, melting, and crystallization of the polyethylene (PE) matrix of PE/OapPOSS-clay nanocomposites were investigated by X-ray diffraction analysis (XRD), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). The results showed that the PE matrix of PE/OapPOSS-clay nanocomposites has lower branching density and higher melting point and degree of crystallinity when compared with those of PE prepared by unsupported catalyst. It is proposed that the chain walking rate of the ethylene polymerization was reduced greatly, resulting in a lower degree of branching because the catalyst has been intercalated into the clay galleries. In order to further investigate the chain branching distribution of the PE matrix of PE/OapPOSS-clay nanocomposites, a DSC technique termed successive self-nucleation and annealing was applied. It was found that the PE matrix of PE/OapPOSS-clay nanocomposites has a larger high melting point fraction, thicker lamella and longer L¯n and L¯w than PE obtained with unsupported catalyst.