Weight-average Molecular Mass Research Articles

Physicochemical characteristics of the active fractions of polyphenols from Arctic macrophytes

Brown algae of the Fucaceae family, collected in the western segment of the Arctic, contain a large number of polyphenolic compounds—phlorotannins—with a unique chemical nature, macromolecular structure, and physicochemical properties, exhibiting bioactive properties. The peculiarity of the biopolymers’ properties and structure, which are an element of fundamental scientific research of the cycle, structure—functional nature—properties, determines the priority of the directions of use of polyphenols as effective biologically active pharmaceutical preparations. This work aims to develop methods for selective extraction of phlorotannins from the Arctic brown alga Fucus vesiculosus, characterization of physicochemical properties, and biological activity of these compounds. The efficiency of solid-phase extraction (SPE) on a hydrophobic sorbent with grafted hexadecyl groups was shown for fractionation of the polyphenolic extract: active fractions were obtained, characterized by a high content of polyphenols (yield of polyphenols up to 98% relative to the content of these components in algae) with mass-average molecular weights of 21.4–35.8 kDa and oligomeric components in the mass range 374–994 Da. The IR spectra of the fractions were characterized, and the tendency of phlorotannins to form aggregates at high concentrations of the extract was shown. During hydrodynamic studies, a strong polyelectrolyte swelling of polyphenols (PP) was noted. The obtained polyphenolic fractions differ in physicochemical characteristics (acid-base and redox properties) and antioxidant activity.

Properties of Polyhexamethylene Guanidine (PHMG) Associated with Fatal Lung Injury in Korea.

The use of humidifier disinfectant (HD) has been determined to be associated with lung injuries (HDLI) in Korea. Although HD brands containing polyhexamethylene guanidine (PHMG) oligomers have been found to cause more HDLI compared to brands containing other disinfectants, the physicochemical properties of PHMG have been poorly defined. We aimed to quantify the PHMG dissolved in HD brands, characterize the number-average (Mn) and weight-average (Mw) molecular masses, and identify the polymerization degree of PHMG. Analysis of the PHMG oligomers was performed using a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF MS) operated in positive-ion reflectron mode. Eight brands of HD containing PHMG were identified. The PHMG concentrations in these brands ranged from 160 to 37,200 ppm (mean = 3100.9 ppm). Concentration was a significant variable among and within HD brands. The degree of PHMG oligomerization fell within the range of two to four. The averages of Mn and Mw were 517.2 g/mol (range: 422–613 g/mol) and 537.3 g/mol (range: 441.0–678.0 g/mol), respectively. Based on the average molecular weight and the degree of polymerization, the PHMG examined here could be regarded as oligomers, which may be associated with the highest proportion of HDLI being caused by PHMG.

Multiscale analysis on multiextruded poly(lactic acid)/organoclay nanocomposites: Insights into the underlying mechanisms of thermomechanical degradation

Due to the growing market and the relatively high price of poly(lactic acid) (PLA), the possibility to recycle PLA has attracted a tremendous attention, aiming to reduce the environmental impact related to the life cycle of PLA‐based products. However, the comprehensive structural and properties changes of PLA and PLA/clay nanocomposites induced by reprocessing are still not clear. In this work, PLA and its organoclay nanocomposites (PCN5) were subjected to repeated extrusion for 1 and 4 cycles to reveal their recycling characteristics by the observation of the changes in the microstructure, thermal and mechanical properties. Gel permeation chromatography, rheology and morphology analyses were utilized to deeply explore effects of the cycle number on the evolution of chemical structures and clay dispersion. It is found that reprocessing leads to a significant reduction in the weight average molecular mass of PLA by 24.0% and of PCN5 by 37.3%, whereas a more uniform dispersion of clay and a stronger clay‐polymer interaction are also found after reprocessing. A direct correlation between the molecular chain scission and deterioration of thermal/mechanical properties is observed both for PLA and PCN5 subjected to reprocessing cycles. The crystallization rate of PLA is suppressed by the addition of clay, while is accelerated by clay after their processing. Additionally, the presence of clay is found to reduce the differences in the thermal stability between the samples reprocessed after 1 and 4 cycles, which is ascribed to the competition between intensive chain scission and better dispersion of clay in the PLA matrix.

Application of Kinetic Models and Response Surface Methodology to Decolorization of Congo Red Dye with Biopolymer B6

Biopolymer B6 produced by Bacillus sp. B6 was investigated regarding its decolorization of the azo dye Congo Red. Chemical analysis showed that biopolymer B6 with a weight-average molecular mass (Mw) of 11 kDa, was mainly composed of 60.6% polysaccharide and 11.8% protein. Fourier transform infrared (FTIR) spectroscopic analysis revealed the presence of carboxyl, hydroxyl and amino groups. Kinetic studies showed that decolorization of Congo Red was a gradual process, equilibrium was reached in 500 min. Pseudo-second order equation was able to provide a realistic description of decolorization kinetic. Kinetic studies indicated that the process for decolorization of Congo Red was mainly controlled by chemical bonding or biosorption, the cause of adsorption could involve valency forces through sharing or exchange of electrons between Congo Red and biopolymer B6. Response surface methodology was employed to optimize the decolorizing conditions. A Plackett–Burman experimental design was used to aid in the first step of optimization. Temperature, biopolymer B6 dosage and CaCl2 dosage were found to be significant factors affecting decolorization of Congo Red. A Box-Behnken statistical design was employed to determine the optimal value of each significant variable. The concentration of Congo Red was 10 mg/L, the optimum conditions were obtained as follows: biopolymer B6 19.3 mg/L; CaCl2 594 mg/L; T = 15.5°C, with the corresponding decolorization capacity of 288 mg/g, which was in close agreement with the predicted value of 290 mg/g. These results demonstrated that biopolymer B6 was a large, acidic proteoglycan complex of 11 kDa, had strong ability for decolorizing the azo dye Congo Red. In addition, biopolymer B6 could have a potential application in domestic wastewater treatment.

Electron-Beam Plasma for Biomass Modification

Applications of nonequilibrium low-temperature oxygen electron-beam plasma (EBP) for the controllable processing of biopolymers (crab shell chitosan and softwood lignocellulose) are described. Water-soluble chitooligosaccharides with weight-average molecular mass $M_{w} = 800$ –2000 Da and polymerization degree varying from dimers to heptamers were obtained after the EBP-stimulated chitosan destruction; trimers being the most predominant. Water solutions of the EBP-produced chitosan oligomers enhanced the seeds germination and stimulated green mass formation in barley Hordeum vulgare. The EBP processing of lignocellulose resulted in its amorphization and formation of additional oxygen containing functional groups at the surface of the biomaterial.

Переход к параметрам модели процесса радикальной полимеризации

A mathematical transition to model parameters is presented, which are decisive in the preparation of a mathematical model of the radical polymerization process taking into account the gel effect. Using the mathematical model of radical thermal polymerization of styrene as an example, the derivation of parameters is considered, taking into account which the values of the number-average and mass-average molecular weights obtained as a result of calculation using similar parameters given in the previously published literature are confirmed. The difference of the study is the description of a step-by-step transition to the model parameters, applicable to the description of the radical polymerization process of other monomers, taking into account the gel effect.

New cyanopyridine based conjugated polymers carrying auxiliary electron donors: From molecular design to blue emissive PLEDs

Three new D-A (Donor-Acceptor) configured conjugated polymers, i.e.PPy1-3, centered on strong electron accepting cyanopyridine scaffold carrying varied auxiliary donors, viz. phenylene (PPy1), biphenyl (PPy2), and fluorene (PPy3) were designed and synthesized as blue emitters for PLEDs. The new polymers were subjected to spectral, thermal, photophysical and electrochemical characterization. Also, computational studies (DFT) were performed on the repeating units of polymer using Turbomole 7.2 V software package at the B3LYP/TZVP hybrid levels. Further, their weight average molecular masses were found to be 38.8 kDa, 38.9 kDa and 57.7 kDa, respectively as determined by GPC technique. Furthermore, the new polymers PPy1-3, were shown to be stable thermally up to 308–374 °C. Evidently, they exhibited good photophysical behavior with their optical energy band gaps of 2.53–2.64 eV. Finally, the polymers PPy1-3 were employed as an active emissive layer in standard ITO/PEDOT:PSS/Polymer/Al configured PLEDs. Interestingly, at 12 V all the newly fabricated devices exhibit a stable blue characteristic electroluminescence with low threshold voltages of 3.40–5.20 V, confirming an efficient injection of electrons in the diodes. From the results, it is clear that, the polymers PPy1-3, can be considered as prospective blue light emitters for PLED application.

EXTRACTION OF LIGNIN FROM SUGARCANE BAGASSE BY DEEP EUTECTIC SOLVENTS (DESs)

Lignin plays a crucial role as a structural material of plant cell walls and is also known as a significant renewable resource that has the potential to be a raw material for producing high value chemicals. The article aimed to research on the extraction of lignin from sugarcane bagasse by environmental method using deep eutectic solvents (DESs) containing choline chloride and formic acid. In the process, lignins dissolved in DESs were isolated from the solution by dilution with water and ethanol. The obtained lignin samples were characterized with UV - Vis (Ultraviolet – visible spectroscopy), FT-IR (Fourier-transform infrared spectroscopy), GPC (Gel permeation chromatography), and 1H-NMR (Proton nuclear magnetic resonance). The initial results showed that the extracted lignin obtained adequately distinct functional groups and the weight average molecular mass of the lignin was about 28265 g/mol.

Isolation and characterization of a novel exopolysaccharide secreted by Lactobacillus mucosae VG1

A novel strain of Lactobacillus mucosae was isolated from a faecal sample of an individual who had adhered to a strict vegetarian diet for nine years. The strain displayed a ropy character when grown on plates and generated a relatively small amount (62 mg/L) of an exopolysaccharide (EPS) when grown in broth culture.The EPS eluted from a size exclusion chromatography column as a single band with a weight average molecular mass of 1.51 × 104 g/mol. Monomer analysis and sugar absolute configuration analysis confirmed that the EPS was a D-galactan. Using linkage analysis in combination with 1D and 2D-NMR spectroscopy, with spectra being recorded for both the native EPS and for the products generated by Smith degradation of the EPS, the following structure was determined for the repeat unit of the polysaccharide: [Display omitted] This is a novel D-galactan and represents the first structure for an EPS produced by a strain of Lactobacillus mucosae to be reported.

MOLECULAR WEIGHT COMPOSITION OF HUMIC ACIDS IN URBAN SOILS (THE NORTHERN ADMINISTRATIVE DISTRICT OF MOSCOW CITY TAKEN AS AN EXAMPLE)

The article provides research results and comparative analysis of humic acids in sod-podzolic soil of the Experimental Forest of the Russian State Agrarian University (protected area) and urban soils located in the Timiryazev district of Moscow. Humic acids of the zonal sod-podzolic soil of the Experimental Forest include four fractions with varying molecular weight: the 1 st fraction – ≥ 23 440 unified atomic mass units (amu), the 2 nd one – 13 340 amu, the 3 rd one – 5 500 amu and the 4 th one – 2 460 amu. The fraction with a molecular weight of 5 500 amu and a relative content of 38 % dominates among them, while the share of low-molecular fractions (< 20 000 amu) accounts for 70 % of the total mass of humic acids. When weight-average molecular mass of humic acids is 17 530 amu, the average molecular mass of the low-molecular fractions is 9 960 amu. Humic acids of urbanozems differ in molecular weight composition from humic acids of sod-podzolic soil. In most cases it consists of 5–6, less commonly of 3, fractions with molecular weight from 1 780 to ≥ 23 440 amu. The share of medium- and high-molecular fractions fluctuates from 31–37 % to 47–50 % of the total mass of humic acids. The characteristic feature of humic acids of urbanozems is the presence in their composition of low-molecular fractions with such molecular weights, which are not found in humic acids of sod-podzolic soil. Thus, humic acids of urbanozems are characterized by higher weight-average molecular mass ranging from 17 680 to 19 980 amu, as well as by higher weigh-average molecular mass of the low-molecular fractions which vary from 10 680 to 13 650 amu.

Separation and Identification of Oligomeric-Hindered Amine Light Stabilizer Uvasorb HA 88 by High-performance Liquid Chromatography (HPLC) Coupled With Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALSI-TOF-MS)

Uvasorb HA 88 is widely used as a light stabilizer to prevent plastic polymer degradation. Its high molecular weight and oligomeric characters provide challenge for quality control. In this study, high-performance liquid chromatography (HPLC) coupled with electrospray ionization time of flight mass spectrometry (ESI-TOF MS) was applied for separation and detection of Uvasorb HA 88. The synthesis scheme was deduced and confirmed by the characterization of Uvasorb HA 88 products from different batches. Direct matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was employed for the detailed characterization of chemical composition of Uvasorb HA 88. Furthermore, a reliable reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with MALDI-TOF MS method was established and the weight-average and number-average molecular masses were calculated. The results revealed that six oligomers with repeat unit numbers from 1 to 4 were present in Uvasorb HA 88. A molecular weight of up to 6808 g mol−1 was detected and two new series of oligomers were reported for the first time. Different series of oligomers and positional isomers were observed in Uvasorb HA 88. This work provides a suitable method to evaluate the technical grade of Uvasorb HA 88 as well as comprehensive characterization of complex oligomeric hindered amine light stabilizers.

Purification, Characterization and Degradation Performance of a Novel Dextranase from Penicillium cyclopium CICC-4022.

A novel dextranase was purified from Penicillium cyclopium CICC-4022 by ammonium sulfate fractional precipitation and gel filtration chromatography. The effects of temperature, pH and some metal ions and chemicals on dextranase activity were investigated. Subsequently, the dextranase was used to produce dextran with specific molecular mass. Weight-average molecular mass (Mw) and the ratio of weight-average molecular mass/number-average molecular mass, or polydispersity index (Mw/Mn), of dextran were measured by multiple-angle laser light scattering (MALS) combined with gel permeation chromatography (GPC). The dextranase was purified to 16.09-fold concentration; the recovery rate was 29.17%; and the specific activity reached 350.29 U/mg. Mw of the dextranase was 66 kDa, which is similar to dextranase obtained from other Penicillium species reported previously. The highest activity was observed at 55 °C and a pH of 5.0. This dextranase was identified as an endodextranase, which specifically degraded the α-1,6 glucosidic bonds of dextran. According to metal ion dependency tests, Li+, Na+ and Fe2+ were observed to effectively improve the enzymatic activity. In particular, Li+ could improve the activity to 116.28%. Furthermore, the dextranase was efficient at degrading dextran and the degradation rate can be well controlled by the dextranase activity, substrate concentration and reaction time. Thus, our results demonstrate the high potential of this dextranase from Penicillium cyclopium CICC-4022 as an efficient enzyme to produce specific clinical dextrans.

New poly(ether imide)s with pendant di-tert-butyl groups: Synthesis, characterization and gas transport properties

Polymers with bulky substituents are of pronounced interest in membrane based separation applications. In this direction, the present work reports the synthesis and characterization of a series pendant di-tert-butyl and trifluorometyl groups containing new poly(ether imide)s (PEIs). The PEIs were prepared by thermal imidization of polyamic acid which is derived by the reaction of a diamine monomer, namely 1,4-bis-[{2′-trifluoromethyl 4′-(4″-aminophenyl)phenoxy}] 2,5-di-t-butylbenzene (FMTBDA) with four different commercially available aromatic dianhydrides, i.e. BPADA, 6FDA, ODPA, and BTDA. The PEIs are soluble in many organic solvents and show reasonably high intrinsic viscosity (0.87 to 1.10 dL/g in NMP) and weight average molecular mass as high as 371,900 g/mol with a polydispersity index of 3.8. The proton NMR and FTIR spectroscopic investigation are in accordance with the respective polymer repeating unit structures. The physical properties of the polymers like thermal and mechanical stability are investigated thoroughly to assess their suitability for membrane based application. The polymers are thermally stable up to 474 °C with 10% weight loss temperature in air environment and have a glass transition temperature as high as 253 °C. The polymer membranes have satisfactory mechanical strength with stress at break value up to 95 MPa. The gas permeability coefficients of the PEIs are somewhat higher than those of other polyimides prepared from the same dianhydrides.

The use of rheological behavior to monitor the processing and service life properties of recycled polypropylene

Abstract The influence of multiple reprocessing cycles on the rheological, thermal and mechanical properties of pre-consumer polypropylene (PP) waste (or manufacturing scrap) was investigated. An increase in the melt flow rate (MFR) and a decrease in the viscosity and the mass average molecular weight were found as well as a narrowing of the molecular weight distribution. As a typical industry practice, manufacturing scrap is often mixed with virgin material. Thus, production material with 70% regrind was also examined. The measured properties followed the same trends as for reprocessing without refreshing. A separate investigation of thermal and thermal oxidative degradation showed a constant MFR at processing temperatures for thermally degraded material and a significant increase for thermal oxidative tests. The results provide a better understanding of the degradation mechanisms of PP and show that the rheological behaviors, MFR and melt viscosity, are well suited to assess these effects.

Study of Rheology of Tannin Obtained from Flower Buds of Terminalia chebula (Aralu) and Formaldehyde Reaction

The gelling and hardening reactions of tannin extracted from flower buds of Terminalia chebula with formaldehyde were analysed by parallel-plate rheometry techniques. In this study, a method to determine the rheological features of tannin-formaldehyde reactions both before and after the gel point was settled. The conversion from the liquid to solid state occurs at the gel point. Before the gel point, the zero shear viscosity can portray the behavior of the liquid resin. The value of this parameter rises as the polycondensation reaction proceeds, and at the gel point the weight average molecular mass turn into theoretically infinite.

Modeling the molecular weight and number average molecular masses during the photo-thermal oxidation of polypropylene using neural networks

This work investigates the potential of artificial neural network (ANN) model to predict the molecular weight (M W ) and number average molecular masses (Mn) during the photo-thermal oxidation of polypropylene (pp). A set of 116 data points were used to test the neural network, 80%, 10%, and 10% of the database were used, or the training, the validation, and the test of the model. The optimal topology of ANN model obtained with the architecture of (3 inputs, 23 hidden and 2 output neurons). Statistical analyses of neural network model show good agreement with experimental data (a coefficient of correlation equal to 0.9864 and 0.9688, and a root mean square error equal to 11.1250 kg/mol and 3.5284 kg/mol for the predicted molecular weight and number average molecular masses respectively), considering, a three layer feed-forward backpropagation neural network with BFGS quasi-Newton (trainbfg) training algorithm, a hyperbolic tangent sigmoid and logarithmic sigmoid transfer function at the hidden and the output layer respectively. The comparison between the experimental and calculated results show that the ANN model is able of predicted the molecular weight and number average molecular masses during the photo-thermal oxidation of polypropylene.

Chicory root pulp pectin as an emulsifier as compared to sugar beet pectin. Part 1: Influence of structure, concentration, counterion concentration

The emulsifying properties of a pectin product vary with its origin. In this work, the structural and emulsifying characteristics of a low-methylated and partially acetylated pectin from chicory root pulp (referred to as CRP) were investigated and used in comparison with sugar beet pectin (SBP). The structural characterizations suggested a few aspects of dissimilarity between CRP and SBP: (a) GalA content, (b) composition of neutral sugars (NS), (c) weight average molecular mass, (d) protein content and amino acid composition, and (e) ferulic acid. CRP was interface-active and thus comparable to SBP in the stabilization of the oil/water emulsion formulated with 15% middle chain triglyceride (MCT). Upon increasing the concentration from 0.25 to 2% w/w, similar downward trends of d32 were observed for CRP and SBP, however, CRP showed relatively better performances at 0.25 and 0.5%. The minimum d32 values for CRP (0.58 ± 0.02 μm) and SBP (0.54 ± 0.02 μm) were achieved at critical concentrations of 1.5% and 2%, respectively. At these critical concentrations, the distribution of droplet sizes of the corresponding emulsions was significantly different. The emulsifying ability of CRP depended largely on the covalently bound proteinaceous moiety, whose contribution was demonstrated by proteinase induced demulsification. The effect of Na+ and Ca2+ on emulsification was also examined; both CRP and SBP were almost unaffected by the addition of Na+ (25–100 mM), whereas CRP was more sensitive to the addition of Ca2+ (25–100 mM). For CRP, the stronger responsiveness to Ca2+ may be due to the weaker hindrance of the acetyl groups. Altogether, we conclude that CRP can be used as a polysaccharide-based emulsifier, particularly for use in stabilizing low-calcium emulsion systems.

Colligative and hydrodynamic properties of aqueous solutions of pectin from cornelian cherry and commercial apple pectin

The analysis of literature revealed a certain lack of knowledge concerning Cornelian pectins, as well as a significant gap in the description of properties of apple pectin, and therefore the purpose of this study was to examine and compare the physicochemical properties of these compounds. Pectins from both sources were obtained using water extraction. Mass distribution was determined for each solution, physicochemical properties were measured using osmometry, DLS, and intrinsic viscosity; Atomic Force Microscopy (AFM) photos of the particles were recorded, together with their FT-IR spectra, and the ζ-potential was measured. Additionally both compounds were compared by X-ray diffraction revealing the amorphousness of the samples. Both polysaccharides exhibit polyion properties, but the results reveal considerable differences between them: industry-grade apple pectins have higher weight average molecular mass with strong dispersion, the Cornelian cherry pectins, unlike industry-grade apple ones, are poorly soluble in water. The Cornelian pectins’ inability to aggregate is quite an unexpected behaviour, as is the presence of protein complexes, which are absent in industry-grade apple pectin.

Atomistic chemical computation of Olefin polymerization reaction catalyzed by (pyridylamido)hafnium(IV) complex: Application of Red Moon simulation

We have realized the microscopic simulation of olefin polymerization, that is, the simulation of the catalytic polymerization (CP) reaction system composed of (pyridylamido)hafnium(IV) complex as the catalyst. For this purpose, we adopted Red Moon (RM) method, a novel molecular simulation method to simulate the complex reaction system. First, according to the previous research, with the help of the QM calculation, we proposed a model system and elementary processes and explained the theoretical treatment of the simulation by the RM method (the RM simulation). In addition, we also proposed a macroscopic simulation based on chemical kinetics simulation. Then, we performed two simulations and compared them in terms of the effective time evolution of the three macroscopic physical quantities, the number-average molecular weight Mn , the mass-average molecular weight Mw , and the molar-mass dispersity ĐM . The comparison showed that the two simulations are in quantitative or partially qualitative agreement with each other. Therefore, it is concluded that the RM simulation could not only simulate the CP reaction process microscopically, but also it is connected essentially to reproduce the time evolution of the macroscopic physical quantities on the basis of its microscopic simulation data. © 2018 Wiley Periodicals, Inc.

Polymer crystallinity and the ductile to brittle transition

The effects of crystallinity and molecular weight on the ductile-brittle transition of a semi-crystalline polyamide were de-coupled. Low molecular weight organic acid solutions were used to accelerate the molecular weight degradation of polyamide-11 to be faster than with water aging at 120 °C. The mass average molecular weight (Mm) of the aqueous acid aged polyamide-11 (PA-11) polymerized from 11- aminodecanoic acid degraded 4 times faster in acetic and 8 times faster in butanoic acid solutions than aging in water. With accelerated Mm degradation, crystallinity increased due to chemi-crystallizaion but at a slower rate than decreases in molecular weight. These accelerated molecular weight degradation techniques made it possible to separate the role of crystallinity from molecular weight on PA-11 ductility. This research on degradation of a semi-crystalline polyamide in acidic solutions and in water shows that reaching a critical crystallinity determines the ductile to brittle phase transition, not chain length as measured by molecular weight.