Degree Of Branching Research Articles

Polymerization of D,L-lactide in the presence of Boltorn™ polyester polyol

Objects. To synthesize monodisperse biodegradable hyperbranched polymers based on D,L-lactide in the presence of Boltorn™ H30 polyester polyol as a macroinitiator.Methods. 1H and 13C nuclear magnetic resonance (NMR) spectroscopy was used to study the chemical structure of the Boltorn™ H30 polyester polyol and (Boltorn™ H30)-PDLA hyperbranched copolymers. The molecular weight distribution of the polymers was studied by gel permeation chromatography (GPC). In order to study the thermal stability of Boltorn™ H30 polyester polyol, thermogravimetric analysis (TGA) was used. Polymerization of D,L-lactide was carried out in a block in the presence of Boltorn™ H30 polyester polyol.Results. The degree of branching of Boltorn™ H30 polyester polyol was calculated from NMR data, while the TGA method was used to determine the upper operational temperature range. The polymerization of D,L-lactide in the presence of Boltorn™ H30 polyester polyol used as a macroinitiator was studied. The molecular weight characteristics of the obtained copolymers were studied by NMR and GPC.Conclusions. Optimum conditions were determined for the polymerization of D,L-lactide when using Boltorn™ H30 polyester polyol as a macroinitiator. The possibility of synthesizing narrowly dispersed hyperbranched polymers (Boltorn™ H30)-PDLA under the described conditions was demonstrated.

Study on catalytic aquathermolysis of heavy oil by simple synthesis of highly dispersed nickel-loaded nitrogen-doped carbon catalysts

Faced with the increasing energy demand, the extraction of heavy oil is crucial. Efficient catalysts can reduce the viscosity and improve the quality of heavy oil. In this paper, the highly dispersed Ni/NC-6.0 catalyst was prepared by one-pot method and was utilized for the viscosity reduction and upgrading of heavy oil. The results of H2-TPD, SEM, TEM, and XPS demonstrate that the average size of Ni/NC-6.0 is about 200 nm, and the Ni atoms coordinated with N atoms are highly dispersed over the surface of carbon support. The experimental results of catalytic aquathermolysis reveal that highly dispersed Ni/NC-6.0 catalyst showed efficient catalytic performance in reducing the degree of asphaltenes branching and cracking the long chains of resin. It can reduce the viscosity by 82.21% and decrease the heavy components by 13.04% through the occurrence of hydrodesulfurization, hydrodenitrogenation, debranching, dealkylation of long-chain, depolymerization, and cracking. This work makes contributions to viscosity reduction and upgrading of heavy oil.

Preparation of resistant glucan by high pressure processing (HPP) and enzymatic methods increases indigestibility

This study describes a new method for producing high-quality resistant glucan by characterizing the structural mechanism of indigestibility. The structures and properties of resistant glucans were characterized before and after in vitro simulated digestion. The results demonstrated that high-pressure processing (HPP) led to the complete disappearance of crystal peaks and increased the efficiency of the two enzymes (α-amylase and transglucosidase). Moreover, α-1,6 and β-linkages were abundant in the connecting parts of the long and branching chains in the resulting resistant glucans, thus hindering the ability of digestive enzymes to hydrolyze short chains with a degree of polymerization (DP) ≤ 6. In addition, transglucosidase activity led to a higher proportion of short chains (DP 3–6), further promoting indigestibility. We demonstrated that, without rectification and decolorization, the dietary fiber content was >75 %, and the degree of branching increased to 50.9 %, indicating higher indigestibility than that resistant glucans produced by traditional methods.

Pore Characteristics and Fractal Dimension Analysis of Tectonic Coal and Primary-Structure Coal: A Case Study of Sanjia Coal Mine in Northern Guizhou.

Understanding the pore heterogeneity of tectonic coal and primary-structure coal is of great significance for predicting and preventing tectonic coal. This study adopts the low-temperature nitrogen adsorption method, mercury injection experiment, and other methods, combined with fractal theory, to quantitatively analyze the pore distribution of coal samples inside and outside the outburst cavities of the Sanjia coal mine. The experiments have shown that the contents of aliphatic functional groups and hydrogen in tectonic coal are higher than those of aromatic structural functional groups. Raw coal has more straight chains than side chains, whereas aliphatic hydrocarbon mostly has short chains, and the branching degree is high. Soft and primary-structure coals have similar elemental content and tectonic effects endow the coal with better connectivity. The pores are filled with particles and flakes, and the surfaces of tectonic coal have more pores and fissures on them. According to the experimental curve, the pores are divided into five types. The pore size of primary-structure coal is mainly type II pores, and the pore size distribution of tectonic coal is relatively wide, with the majority being class I and class II pores. The specific surface area of tectonic coal is 60.7% more than that of primary-structure coal. The box fractal dimension of coal decreases with the increase in scanning electron microscopy (SEM) magnification. The minimum fractal dimension of tectonic coal is 2.49, which is 7.8% lower than the peak of 2.70. It can be seen from the fractal dimension that the fractal dimensions of pore types II, III, and IV are rougher.

Influence of Silica-Supported Alkylaluminum on Heterogeneous Zwitterionic Anilinonaphthoquinone Nickel and Palladium-Catalyzed Ethylene Polymerization and Copolymerization with Polar Monomers

The development of the heterogeneous late transition metal-catalyzed olefin (co)polymerization is a challenge in current research. Here, we report the preparation of heterogeneous anilinonaphthoquinone nickel and palladium catalysts by the binding of SiO2-supported alkylaluminums to a quinone oxygen of the ligand (Mt-AlR3/SiO2). The heterogeneous nickel catalyst exhibited a very high activity (up to 10.4 × 106 g mol–1 h–1) for ethylene polymerizations to produce semicrystalline high-molecular-weight (Mn up to 54.3 × 104 g mol–1) polyethylenes with a low degree of branching (<11.1/1000 C), high Tm values (121–131 °C), and well-regulated particle morphologies. The polymerization behavior depended on the electron density of the metal center modulated by the Lewis acidity of the remotely bound alkylaluminum as can be analyzed and verified through model optimizations and density functional theory (DFT) calculations. Most importantly, these nickel catalysts were able to produce semicrystalline ethylene/5-hexene-1-yl copolymers with a high activity and high molecular weight. The heterogeneous palladium catalyst can promote the copolymerization of ethylene with commercial methyl acrylate or polar norbornene derivatives with a moderate activity, affording a polar functionalized polyethylene and a cyclic olefin copolymer.

Synthesis of Poly(glycerol butenedioate)-PGB-Unsaturated Polyester toward Biomedical Applications.

A new polyester poly(glycerol butenedioate) (PGB) was obtained in the bulk polycondensation of glycerin and maleic anhydride. Glycerol polyesters are new biomaterials commonly used in tissue engineering. PGB, containing the α,β-unsaturated moiety, could be very interesting due to potential modifications such as additions or oxidation. Such modifications are not possible on the heretofore known glycerol polyesters due to their structure without α,β-unsaturated moieties. In this work, the developed process was optimized by applying the design of experiments. The optimization criterium was the minimization of the E/Z isomer ratio. Applying the two-stage process, the E/Z isomer ratio was reduced from 5.5 to 0.5 compared to the one-stage process. The degree of branching was also reduced from 17 to 9%, as well as the degree of esterification from 0.89 to 0.72. The obtained structure can be used in modifying or cross-linking via Michael additions.

Production of a high molecular weight levan by Bacillus paralicheniformis, an industrially and agriculturally important isolate from the buffalo grass rhizosphere.

A new exopolysaccharide (EPS) producing Gram-positive bacterium was isolated from the rhizosphere of Bouteloua dactyloides (buffalo grass) and its EPS product was structurally characterized. The isolate, designated as LB1-1A, was identified as Bacillus paralicheniformis based on 16S rRNA gene sequence and phylogenetic tree analysis. The EPS produced by LB1-1A was identified as a levan, having β(2 → 6) linked backbone with β(2 → 1) linkages at the branch points (4.66%). The isolate LB1-1A yielded large amount (~ 42g/l) of levan having high weight average molecular weight (Mw) of 5.517 × 107Da. The relatively low degree of branching and high molecular weight of this levan makes B. paralicheniformis LB1-1A a promising candidate for industrial applications.

Coupling between acid precipitation and resin adsorption for purifying alkaline extracted hemicellulose from sugarcane bagasse

Hemicellulose is considered the second most renewable component in lignocellulosic biomass after cellulose, and can be used in value-added industrial applications including medical dressing, packaging materials and hydrogels. Hence, the purification methods of different acid precipitation conditions, ethanol precipitation and resin adsorption were investigated. In this paper, the results showed that most of the lignin was removed by acid precipitation. With the adjustment of pH value from 6 to 2 by acid precipitation, the less lignin remains in hemicellulose samples, the higher the purity of hemicellulose. After resin adsorption treatment, the molecular weight of hemicellulose increased slightly and the weight average molecular weight of Ha2 (Ha2 is hemicelluloses precipitated at pH = 2) is 7.91 × 104 g/mol among, the branching degree of hemicellulose decreased slightly, the thermal stability of hemicellulose increased slightly. It can be shown from 2D HSQC NMR that the structure of hemicellulose did not change significantly before or after adsorption and at different pH values. Trace lignin-carbohydrate complexes (LCCs) structures were remained in hemicellulose sample. The slight loss of hemicellulose caused by resin adsorption is due to LCCs. The sensitivity of XAD-16N resin to phenyl glycoside bond (PhGlc) of different forms was different.

Partial hydrolysis of waxy rice starch by maltogenic α‐amylase to regulate its structures, rheological properties and digestibility

SummaryAlthough different types of starch have been modified with maltogenic α‐amylase (MGA), its behaviour on waxy rice starch (WRS) remains obscure. This study aimed to modify cooked WRS with high concentration using MGA. The molecular weight of WRS decreased from 1.8 × 107 to 4.1 × 106 Da due to the exo–endo activity of MGA, while a high proportion of short branch chain and branching degree were generated as the degrees of hydrolysis (DH) increased. Intriguingly, no retrogradation occurred for the hydrolysates, even at DH 4.65%. Rheology reveal that the hydrolysate systems exhibited better fluidity and thixotropy. Furthermore, the resistant starch content of cooked WRS was elevated by 10.43% after MGA modification. The results indicate that MGA‐modified WRS was superior to other starches that have been reported in terms of inhibition of retrogradation and resistant starch content. Our data demonstrate the potential of enzyme‐based protocol for WRS modification using MGA alone to acquire clean and functional starch.

A novel bioderived AB2‐type monomer from castor oil derivative for the preparation of fully biobased hyperbranched polyesters

AbstractDesigning biobased hyperbranched polyesters from vegetable oil has been attracting considerable interests from academic industrial communities. Herein, a novel fully biobased hyperbranched polyester (HBPE) was prepared by self‐condensation of AB2‐type bioderived monomer based on methyl ricinoleate (MR), a castor oil‐derived renewable chemical. The reaction conditions were optimized to obtain the AB2‐type monomer in a high conversion ratio (up to 87%). The self‐condensation of AB2‐type monomers was carried out in the presence of two kinds of transesterification catalysts (Ti(OBu)4 versus Zn(Ac)2), among which Ti(OBu)4 was found to be more efficient one and yield higher molecular weights in the range of 5800~11,500 g/mol. The resulting HBPEs were characterized in terms of Fourier transform infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. The degree of branching was calculated to be 0.33~0.39. Thermal analysis revealed that the as‐prepared HBPEs were amorphous with tunable glass transition temperatures ranging from −44.8 to −24.6°C. All the prepared HBPEs exhibited good thermal stability with the maximum onset decomposition temperature (Tonset) up to 294.6°C. These structural features and properties of resulting biobased HBPEs enabled them to act as a potential ‘greener’ additive for polymers.

Structure-Dependent Nontraditional Intrinsic Fluorescence of Aliphatic Hyperbranched Polyureas.

The nontraditional intrinsic fluorescence (NTIF) of polymers containing heteroatoms has gained considerable attention due to its promising applications in label-free bioimaging. Aliphatic hyperbranched polyureas (aBPUs), which have recently shown great promise in the field of nanomedicine, bear controllable urea groups distributed on the branch points and thus are potential candidate luminogens. However, their NTIF properties and how their structures influence the NTIF properties have not been illustrated yet. Here, we addressed these issues by synthesizing a series of aBPUs with different degrees of branching (DBs) or different modifications. aBPUs exhibited an obvious NTIF phenomenon and with the increase of DBs, the NTIF enhanced as well. Chemical modifications either at the branching ends or in the interior of aBPUs could affect the NTIF performances, which were highly dependent on the types of modification. Disruption of the intra-/intermolecular hydrogen-bonding interactions decreased the NTIF. In addition, poly(ethylene glycol) (PEG)-modified aBPUs could self-assemble into nanospheres, and the formation of nanoassembly led to 89% enhancement on NTIF compared with the homogeneous solution of aBPUs-PEG in dimethylformamide (DMF). Finally, aBPUs-PEG nanoassembly demonstrated a capability in realizing label-free material imaging in vitro. These results shed light on the rational design of the polymer structures to achieve desired fluorescence with unconventional luminophores.

Oil‐Based versus Bio‐Based C8 Alkyl Chain (Meth)Acrylates in Emulsion Polymerization: Kinetics and Microstructure

Abstract2‐Octyl acrylate (2‐OA) is a very promising bio‐based monomer that is a great candidate to substitute the widely used (but oil‐based) 2‐ethylhexyl acrylate (2‐EHA). In this work, the homopolymerization of these two monomers along with their methacrylic analogues (2‐octyl methacrylate, 2‐OMA and 2‐ethylhexyl methacrylate, 2‐EHMA) is compared to analyze their performance in detail. Very similar polymerization kinetics are observed, both in conversion and particle size. However, there are important differences in the microstructure (molar mass distribution, gel content, and degree of branching). Both acrylates form high amounts of gel (2‐OA higher than 2‐EHA) while the methacrylates do not form any. It is found that the most likely reason for the higher amount of gel on 2‐OA lies on the second abstractable labile hydrogen in the side chain presented in this monomer, that is more reactive in 2‐OA than in 2‐EHA. This is supported by the molar mass distributions, that show that 2‐octyl esters have higher molar mass than their respective 2‐ethylhexyl counterparts (both in acrylates and methacrylates), as a result of a higher amount of long chain branches.

Effect of thermosonication on texture degradation of carrot tissue in relation to alterations in cell membrane and cell wall structure

Thermosonication as an alternative to hot water blanching of carrots, the effect of thermosonication on the carrot texture and cell structure required deep investigation. This study was conducted from the aspects of cell membrane, cell water, and cell wall pectin. Results showed that thermosonication at 60 °C significantly increased carrot tissue hardness by up to 10.3% compared with fresh. Rheological curves showed that the carrot tissues remained rigid after thermosonication. Cell membrane permeability was damaged to different extents during processing, inducing bound and immobilized water to migrate to free water and bring intracellular electrolytes to outflow. Thermosonication affected cell structure by altering the characteristics of pectin, including uronic acids and neutral sugar contents, degree of linearity and branching, and degree of methoxylation. The modified pectin can seize more divalent cations such as Ca2+ retained in the thermosonicated carrot cell wall, conducive to preserving the textural property of processed fruits and vegetables.

First-order Layer in Artificial Pain Pathway

The neural mechanisms involved in pain perception consist of a pathway which carry signals from the periphery to the cerebral cortex. First-order pain neurons transduce the potentially damaging stimuli detected by the sensorial extremes into long-ranging electrical signals that are transmitted to higher order neurons where the organisation is more heterarchical, especially in the cerebral cortex. However, the first order neurones, as their name states, have a degree of branching which clearly identifies them as hierarchical elements in the arrangement of pain pathway. This research aims to develop an artificial neural pain pathway that mimics this biological process, in particular the first order neurones. First, the research proposes the periodogram method on the condition monitoring data with a minor malfunction and operational damage. As the pain is associated with actual or potential tissue damage, using such data from a machinery system can provide insights which can be used to improve the computational effectiveness. Then, a one-dimensional convolutional neural network model is introduced to represent the second and third orders of the pain pathway. The research findings found clear support for studying the similarities between the major components of biological information processing of tissue damage and statistical signal processing for damage estimation.

Separation of Branched Alkanes Feeds by a Synergistic Action of Zeolite and Metal‐Organic Framework

Zeolites and metal‐organic frameworks (MOFs) are considered as “competitors” for new separation processes. The production of high‐quality gasoline is currently achieved through the total isomerization process that separates pentane and hexane isomers while not reaching the ultimate goal of a research octane number (RON) higher than 92. This work demonstrates how a synergistic action of the zeolite 5A and the MIL‐160(Al) MOF leads to a novel adsorptive process for octane upgrading of gasoline through an efficient separation of isomers. This innovative mixed‐bed adsorbent strategy encompasses a thermodynamically driven separation of hexane isomers according to the degree of branching by MIL‐160(Al) coupled to a steric rejection of linear isomers by the molecular sieve zeolite 5A. Their adsorptive separation ability is further evaluated under real conditions by sorption breakthrough and continuous cyclic experiments with a mixed bed of shaped adsorbents. Remarkably, at the industrially relevant temperature of 423 K, an ideal sorption hierarchy of low RON over high RON alkanes is achieved, i.e., n‐hexane ≫ n‐pentane ≫ 2‐methylpentane > 3‐methylpentane ⋙ 2,3‐dimethylbutane > isopentane ≈ 2,2‐dimethylbutane, together with a productivity of 1.14 mol dm−3 and a high RON of 92, which is a leap‐forward compared with existing processes.

Changes in chemical composition and starch structure in rice noodle cultivar influence Rapid Visco analysis and texture analysis profiles under shading.

GuichaoII, a rice variety with high amylose content widely used to make rice noodles, exhibits high hardness (631.07-729.43), gel consistency (8.47-9.47mm), and hold viscosity/peak viscosity (HPV/PKV) (0.85-0.88); however, it has a low protein content (5.74-6.96%) and swelling factor (5.49-9.77). Herein, GuichaoII was subjected to low-light stress (53% reduction) during the grain filling stage. The amylose content and crystallinity of GuichaoII and the control variety Shuhui 498 decreased while the protein content, short-chain branch ratio, and degree of branching increased, which affected the ability of the rice flour to absorb water and expand during the gelatinization process. The PKV, HPV, breakdown viscosity, and final viscosity were significantly reduced, while the hardness was significantly increased, and the gel consistency and the gelatinization quality of the rice were reduced, severely limiting the processing and production of rice noodles.

Pueraria lobata starch regulates gut microbiota and alleviates high-fat high-cholesterol diet induced non-alcoholic fatty liver disease in mice

The dried roots of Pueraria lobata (Willd.) Ohwi as an edible medicinal herb are enriched with starch. However, the structure, physiology, and biological bioactivity of P. lobata starch (PLS) has not yet been fully investigated. This study showed that PLS consisted of mixed population of granules with polyhedral or spherical surface. The apparent content of resistant starch was 23.14%, and the molecular weight was 1.93 × 107 Da. PLS showed a branching degree and an average polymerization rate of 2.06% and 20.74%, respectively, with fairly high proportion of B1 short chains. The solubility and swelling power of PLS were 38.51% and 28.10 g/g, respectively, showing high hot stability of the viscosity. In vitro fermentation of PLS resulted in specifically altered composition of gut microbiota and increased production of SCFAs, showing a potential prebiotic effect. Moreover, PLS remarkably alleviated inflammation, hepatic steatosis and dyslipidemia in mice with high-fat high-cholesterol diet induced non-alcoholic fatty liver disease (NAFLD). The protective effect of PLS was associated with amelioration of NAFLD-associated gut dysbiosis through specifically increasing the abundance of Lactobacillus, Bifidobacterium and Turicibacter, and decreasing Desulfovibrio. The results would support the use of PLS as a functional prebiotic for protecting against NAFLD.

The influence of amylose content on the modification of starches by glycogen branching enzymes

Glycogen branching enzymes (GBEs) have been used to generate new branches in starches for producing slowly digestible starches. The aim of this study was to expand the knowledge about the mode of action of these enzymes by identifying structural aspects of starchy substrates affecting the products generated by different GBEs. The structures obtained from incubating five GBEs (three from glycoside hydrolase family (GH) 13 and two from GH57) on five different substrates exhibited minor but statistically significant correlations between the amount of longer chains (degree of polymerization (DP) 9–24) of the product and both the amylose content and the degree of branching of the substrate (Pearson correlation coefficient of ≤−0.773 and ≥0.786, respectively). GH57 GBEs mainly generated large products with long branches (100–700 kDa and DP 11–16) whereas GH13 GBEs produced smaller products with shorter branches (6–150 kDa and DP 3–10).

Preparation of Slowly Digested Corn Starch Using Branching Enzyme and Immobilized α-Amylase.

The aim of this study was to modify the digestibility and structure of corn starch by treatment with compound enzymes. Corn starch was treated with two enzymes (α-amylase, which catalyzes hydrolysis, and branching enzyme, a transglycosidase that catalyzes branch formation), and the reaction was monitored by determining the content of slowly digestible starch in the reaction product. The fine structure and physical and chemical properties of enzyme-modified starch samples were analyzed using scanning electron microscopy, gel chromatography, and X-ray diffraction methods; modified starch has a high degree of branching, a high proportion of short-chain branched structures, and greatly improved solubility. The results show that the slow digestion performance of corn starch was significantly improved after hydrolysis by α-amylase for 4 h and treatment with branching enzyme for 6 h. These results show that enzymatic modification of corn starch can improve its slow digestibility properties.

Highly branched starch accelerates the restoration of edible quality of dried rice noodles during rehydration

Rice noodle with excellent edible quality usually needs a dense gel network structure, but the dense structure is detrimental to the entry of water molecules during dried rice noodle rehydration. To combine the conflict requirements, we described the branching modification of rice starch using 1,4- α- glucan branching enzyme (GBE). Highly branched starch with a short cluster structure reduced fractal dimension and crystallite thickness while increasing mesh size and hydrophilicity of rice noodle gel network. Rice noodles derived from rice soaked with 128 U/g of GBE had a desirable rehydration time (370 s), which was reduced by 39.84% compared to the control. Meanwhile, the shorter double helix formed by the short cluster contributed to the improved short-range order, resulting in GBE-modified rice noodles with significantly higher tensile strength than control. These findings demonstrate that manipulating the branching degree of starch is an effective method for producing high-quality instant rice noodles.