Greater Molecular Weight Research Articles

Adaptability of Polymer Molecular Coil Dimension in the Pore Structure of the Reservoir

A series of experiments was carried out to study the matching relationship between the pore structure in the reservoir and the molecular radius of gyration. The hydrodynamic radius Dh (molecular coil dimension) was tested by dynamic light scattering and was be used to characterize the crimping degree of polymer chains and molecular coil dimension. The storage modulus and loss modulus were studied through creep recovery. CT scan was used to measure the parameters of pore throat structure in the reservoir. Finally, a polymer injection experiment has been carried out to evaluate the adaptability of polymer molecular coil dimension in the pore structure of the reservoir. Comparing pore radius with the molecular radius of gyration, it was shown that the storage modulus ratio is the key critical factor of oil displacement efficiency and its value is in the range of 10-20. It was also shown that the optimal stable pressure gradient is in the range of 0.05-0.3 MPa/s; a medium stable pressure gradient of 0.3-0.6 MPa/s is acceptable; and a stable pressure gradient above 0.6 MPa/s or no stable pressure gradient is poor. Greater molecular weight and higher concentration of polymer in the core with low permeability do not provide stable pressure.

IDENTIFICATION OF WATER-SOLUBLE COMPOUNDS CONTAINED IN AQUEOUS EXTRACTS AND FRACTIONS OBTAINED FROM LEAVES OF Ugni Molinae TO DETERMINE THEIR EFFECT ON THE VIABILITY OF HUMAN GASTRIC CANCER CELLS

Ugni molinae Turcz. Myrtaceae (Murtilla) is a plant native to Chile. There is evidence about the antiproliferative compounds present in fruits, but there is no evidence on the antiproliferative activity of the compounds in the leaves. These compounds have importance because they predominate in the popular form of ingestion of leaves. In the present study, the identification of water-soluble components of leaves of U. molinae and a fractionation were carried out to determine the effect on viability of gastric adenocarcinoma cells (AGS). A decoct of leaves was performed at 1%. For the separation of fractions, a countercurrent system (CPC) was used. Leaves were collected and identified by thinlayer chromatography and liquid chromatography-mass spectrometry (HPLC MS/MS). Samples were evaluated to determine the viability of AGS cells by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromidefor (MTT) assays. Three large fractions were identified. In the first one, the phenolic compounds of medium polarity and low molecular weight (phenolic acids) are found. In The second fraction shows low concentrations of phenolic compounds with greater molecular weight (glycosylated and gallolylated flavonoids); and the third, has a predominance of hydrolysable tannins, procianidins and other highly hydrophilic compounds. About cell viability, it was found that, the 1% extract is the one that presented the best effects on cell viability inhibition, in comparation to tannin and flavonoid fractions. In conclusion, there is synergy in the compounds present in the aqueous extract, which causes greater inhibition of cell viability, unlike the separated fractions.

Physicochemical properties of different-sized fractions of sweet potato starch and their contributions to the quality of sweet potato starch

Sweet potato starch consists of granules varying in size. However, the size-dependence of its physicochemical properties and the contribution of different-sized fractions to the functionality of unfractionated starch are not well recognized. These were addressed in the present study by comparing the whole starch with its small-, medium- and large-sized fractions. In composition, the contents of protein, lipid and ash decreased but the apparent amylose content increased by an increase in granule size. The large-sized fraction had significant higher relative crystallinity than its counterpart small- and medium-sized fractions. The degree of short-range order calculated from deconvoluted FTIR spectra for large-sized fraction was identical to the whole starch and showed the lowest degree of order. On the molecular level, larger-sized granules had amylose populations with greater molecular weight. Small-sized fraction had lower average chain length of amylopectin, more DP 6–12 chains but less DP > 25 chains. Insignificant difference in thermal properties was observed among the unfractionated starch and its different-sized fractions. Breakdown, setback and consistency coefficients as well as resistance to digestion showed significantly positive correlation with granule size. However, the pasting temperature negatively correlated with granule size (r = -0.994, p < 0.05). An additive effect on pasting behavior but a non-additive effect on rheological properties was estimated by the weighted summation of individual-sized fraction. Results suggested that the significant impact of granule size on the functionalities of sweet potato starch, which could provide useful information for the utilization of these different-sized fractions.

The role of dye molecular weight on the decolorization performance of the electrocoagulation

Comparative results of color removal performances of Reactive Blue 198 (RB198), Reactive Yellow (RY145) and Reactive Blue 19 (RB19) by electrocoagulation process are presented. Our primary objective was to investigate whether the dye molecular weight affects color removal performance. Dye removal costs of each dye were calculated and compared. Experiments were performed at current densities of 1.04, 2.08, 4.17 and 10.42 A/m2 in electrocoagulation (EC) reactor with aluminum electrodes connected parallel monopolar configuration. Laboratory-scale experiments were run in batch mode with 0.5 L synthetic dye solution volume and 50 mg/L initial dye concentration. Results showed that the color removal efficiencies were directly influenced by the molecular weight of the dyes. The color removal efficiency of the dye with the greatest molecular weight (RB198) was the highest, whereas the color removal efficiency of the dye with the smallest molecular weight (RB19) was the lowest. Moreover, results indicated that the operating cost of RB198 was significantly lower (2.91 $ per kg dye removed) than RY145 (6.61 $ per kg dye removed) and RB19 ($6.72 per kg dye removed) at a current density of 4.17 A/m2.

Baobab polysaccharides from fruits and leaves

Polysaccharides have been isolated at pH 6.0 or 2.0 from fruits and leaves of two varieties of baobab (Adansonia digitata L.). The isolation protocol was designed to study the influence of pH on the structural and functional characteristics of polysaccharides. The polysaccharides were examined by means of sugar composition analysis, NMR spectroscopy, size exclusion chromatography (SEC) and dilute solution viscometry. Polysaccharide yield was substantially higher in fruits (~20% w/w) than in leaves (~4% w/w) with all samples having low protein content (<~0.5% w/w). Monosaccharide and NMR analysis revealed that polysaccharides extracted from leaves have characteristics of “linear” and “branched” pectins (~71 mol% uronic acids, ~12 mol% rhamnose and ~9 mol% galactose) whereas those from fruits were primarily xylogalacturonans (~69 mol% uronic acids, ~13 mol% xylose). Polysaccharides from leaves had greater molecular weight (>300 × 103 g mol−1) than fruits (<200 × 103 g mol−1) presenting distinct solution behaviour. Polysaccharides from leaves were only dispersed at low concentrations (~1% w/v) whereas those from fruits may be dispersed at >20% w/v, representing a clear divide in their functional properties and potential applications. Overall, baobab fruits and leaves offer a novel source of polysaccharides for the food or pharmaceutical industries.

Investigation of eluted characteristics of fulvic acids using differential spectroscopy combined with Gaussian deconvolution and spectral indices.

The characteristics of subfractions of soil fulvic acid (FA3, FA5, FA7, FA9, and FA13) using stepwise elution from XAD-8 resin with pyrophosphate buffers were investigated by differential absorption spectroscopy (DAS) and differential fluorescence spectroscopy (DFS) combined with mathematical deconvolution and spectral indices. The log-transformed absorbance spectra (LTAS) exhibited three regions for both acidic-buffer-eluted subfractions (AESF) and neutral-buffer-eluted subfraction (NESF) and four regions for basic-buffer-eluted subfractions (BESF) according to the differences in spectral slopes. The DAS spectra of FA subfractions were closely fitted with seven Gaussian bands with maxima location at 199.66, 216.18 ± 1.50, 246.20 ± 3.85, 285.22 ± 7.26, 345.64 ± 5.30, 389.27, and 307.37nm, respectively (R2 > 0.993). The content of salicylic-like and carboxyl groups in FA subfractions decreased, while the phenolic chromophore increased with elution sequence. From the 11 spectral indices, AESF had greater molecular weight, condensation, polymerization, hydroxyl radical production, humification degree, and terrigenous contribution, as well as contained more conjugated aromatic structures and less N-containing groups than NESF and BESF. The humification degree and humic characters of FA subfractions were closely associated to the aromaticity, molecular condensation, and DOM-metal-bound functional groups. The proper separation of FA into subfractions is beneficial for reducing its complexity and heterogeneity, which helps us to further explore its chemical properties and interactions with various contaminants in soil environments. Graphical abstract.

SYNTHESIS AND CHARACTERIZATION OF THREE ORGANOTIN(IV) CARBOXYLATE OF ENT-KAURENOIC ACID: ANTIFUNGAL ACTIVITY AGAINST TRAMETES VERSICOLOR (L.: FR) PILÀT

The forest products industry has a very important role in the development toward a sustainable, biobased society. However, many fungi that deteriorate the main structural components of wood, such as cellulose, hemicellulose and lignin, are able to cause decay in standing trees, leading to significant losses in forest output due to impacts on biomass production. Trametes versicolor (L.: Fr) Pilát is a fungus able to attack the trees by saprotrophic and parasitic life strategies, causing white-rot of wood species, a serious problem for the industry that is focused on wood and its uses. The objectives of the work were the synthesis of organotin(IV) carboxylate of a natural product (ent-kaurenoic acid), characterization of the structures and anti-fungal evaluation against T. versicolor, as a contribution of new alternatives for the wood preservation. The synthesis of organotin(IV) complexes derived from the diterpene tetracyclic ent-kaur-16-en-19-oic acid (ent-kaurenoic acid, KA) gave three new complexes potentially active against T. versicolor. The complexes were characterized by FTIR and NMR spectroscopy. The biological activity was evaluated by a gel dilution method with superficialplate inoculation, using 60 and 120 μg/mL concentration, for the KA and the three organotin(IV) complexes. A considerably higher bioactivity was observed to the 120 μg/mL concentration, and for the complex with greater molecular weight.

Polymeric Stabilization of Nano‐Scale HMX Suspensions During Wet Milling

AbstractThe focus of this paper is to investigate the polymeric stabilization of cyclotetramethylene tetranitramine (HMX) suspensions using polyvinylpyrrolidone (PVP). The PVP adsorption on HMX surface was studied using zeta potential measurements, which revealed that the shorter PVP polymer chain (lesser molecular weight) adsorbed better than the longer one (greater molecular weight). This study also showed that the solvent dramatically affects the PVP adsorption. A turbidity test was conducted, showing that lower molecular weight PVP offers better stability. This stability is enhanced by increasing the ethanol concentration. The depletion mechanism was responsible for HMX stabilization with ethanol. Finally, a milling study was conducted to compare the HMX with and without a stabilization mechanism. This study indicated that PVP in 50 % water/50 % ethanol was able to stabilize HMX by depletion and reduce the size to 180 nm within 10 minutes of milling. Strong aggregation was observed for HMX milled in the absence of the stabilization mechanism. The stabilization techniques discussed in this study appeared to lead to a shorter processing time and a more efficient milling process when utilized. Under comparable milling conditions, a particle size of 180 nm could be achieved with stabilization compared to 500 nm without. Such a dramatic improvement of the milling process bodes well for future nanoHMX production, as well as that of similar materials.

Chitosan/β-glycerophosphate in situ gelling mucoadhesive systems for intravesical delivery of mitomycin-C

The development of mucoadhesive in situ gelling formulations for intravesical application may improve the therapeutic outcomes of bladder cancer patients. In this work, chitosan/β-glycerophosphate (CHIGP) thermosensitive formulations have been prepared using three different chitosan grades (62, 124 and 370 kDa). Their ability to form in situ gelling systems triggered by changes in temperature upon administration to urinary bladder were evaluated using vial inversion and rheological methods. Texture analysis was used to study their mucoadhesive properties as well as syringeability through the urethral catheter. The retention of CHIGP formulations, with fluorescein sodium as the model drug, was studied on porcine urinary bladder mucosa ex vivo using the flow-through technique and fluorescent microscopy. CHIGP formulations containing mitomycin-C were prepared and drug release was studied using in vitro dialysis method. It was established that the molecular weight of chitosan influenced the thermogelling, mucoadhesive and drug release behaviour of the in situ gelling delivery systems. Formulations prepared from chitosan with greatest molecular weight (370 kDa) were found to be the most promising for intravesical application due to their superior gelling properties and in vitro retention in the bladder.

Synthesis of sodium polyacrylate copolymers as water-based dispersants for ultrafine grinding of praseodymium zirconium silicate

A series of sodium polyacrylate copolymers (i.e., poly acrylic acid-co-itaconic acid-co-2-acrylamide-2-methylpropanesulfonic acid or PSIA with different molecular weights and monomer molar ratios) were synthesized based on acrylic acid-co-itaconic acid (PAI) as water-based dispersants for ultrafine grinding of praseodymium-doped zirconium silicate (Pr-ZrSiO4). The particle size/size distribution, suspension rheology and dispersant adsorption were analyzed by laser particle size analysis, rheometry, Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG) and electrokinetic potential measurement, respectively. Compared to the dispersant PAI, the use of the dispersant PSIA1 with a greater molecular weight in the Pr-ZrSiO4 suspension ground for 45 min at pH values 7.0–8.0 can give a finer product with the narrower particle size distribution. The dispersant PSIA1 used in ultrafine grinding has a suitable viscosity of the suspension and generates more hydrogen bonds on the particle surface, and sulfonic acid group in the dispersant PSIA1 can provide a greater charge density than carboxylic acid groups in the dispersant PAI. In addition, the total potential energies between the particles in suspension with different copolymer dispersants at different pH values were also calculated. It is indicated that the effective ultrafine grinding of the particles is related to the total interparticle potential energy provided by the dispersant PSIA1 at pH 7.0–8.0.

Two horseradish peroxidase-based modifications result in two milk protein products with ordered secondary structure and enhanced in vitro antigenicity

ABSTRACTIn this study, two horseradish peroxidase (HRP)-based modifications were used to treat whey protein isolate (WPI) and skim milk powder (SKMP) at protein concentration of 50 g/L, pH 7.0, and 37°C, via dityrosine formation in protein molecules. When HRP, glucose oxidase, and glucose were used to treat WPI and SKMP, suitable usages of HRP, glucose oxidase, and glucose, and reaction time were selected from single factor trials based on relative dityrosine contents of the modified products. After that, the selected HRP plus the calculated H2O2 were used to treat WPI and SKMP. Electrophoretic analysis demonstrated that the modified products contained some cross-linked proteins with greater molecular weights. Other analyses showed that the modified products had more ordered secondary structure, and higher in vitro α-lactalbumin and β-lactoglobulin antigenicity than the respective substrates. HRP–glucose oxidase–glucose system was more potent than HRP–H2O2 system to enhance in vitro antigenicity of WPI and SKMP.

Study on the Characterization and Evaluation Methods of PA6 Chips for High-Speed Spinning

Abstract The reasons for the significant difference of PA6 spinnability are discussed. For this research project, BASF PA6 chips (BASF, Germany) and PA6 chips (GC, China) were chosen as research objects. We chose these two different chips because BASF PA6 chips are stable and GC PA6 chips are unstable in high-speed spinning. The measurement of relative viscosity, crystallization rate, content of extractable matter, molecular weight and its distribution, and Fourier transform infrared (FTIR) spectroscopy of extractable matter were systematically investigated. Moreover, the screw extrusion process of PA6 melt in high-speed melt spinning was simulated by a capillary rheometer, in which PA6 samples with different melting times were prepared to conduct the above-mentioned tests. Compared to BASF chips, the GC chips have the higher content of extractable matter, the greater and more variable relative viscosity, the greater molecular weight, and the wider distribution, causing the poorer spinnability in high-speed spinning. Furthermore, the extractable matter in GC chips is the same as that in BASF chips, which is confirmed by FTIR spectra.

Temperature resistance and salt tolerance of starch derivatives containing sulfonate groups

In this study, novel anionic starch derivatives (2,4‐bis(diiminobenzenesulfonic acid disodium salt)‐[1,3,5]‐triazine‐6‐yl)‐starch (BSTSS) were prepared by reacting 2,4‐bis(diiminobenzenesulfonic acid disodium salt)‐6‐chloro‐[1,3,5]‐triazine with natural corn starch. The molecular weight of samples with different degrees of substitution (DS) was analyzed by gel permeation chromatography, and their structures were characterized by Fourier‐transform infrared spectroscopy. The rheological properties of BSTSS were evaluated using a rotational viscometer. Results indicated that the starch derivatives had a greater molecular weight (Mw = 2.57 × 106 to 3.12 × 106) and lower viscosity (η(DS = 0.10, C = 1%) = 133.27 mPa s; η(DS = 0.56, C = 4%) = 586.83 mPa s) than carboxymethyl starch at the same DS and concentration. The samples with different DS exhibited good viscosity stability from pH 2 to 12 and good temperature resistance from 25 to 60°C. The addition of salts exerted a more pronounced effect on the viscosity of BSTSS solution, and the viscosity of the solution increased with the addition of NaCl and CaCl2.

Influence of glycerol on morphology and properties of polylactide/montmorillonite nanocomposites

The widespread use of polymers from renewable sources is currently unachievable, not only by economic constraints but by the limiting properties of this type of material. Several strategies have been developed to overcome this problem; one of the most extensively explored is the use of nanofillers to improve the biopolymer’s properties such as stiffness, impact strength and gas barrier, amongst others. However, several gaps in understanding the morphology formation of these systems still exist. This study evaluates the use of glycerol as an auxiliary additive during production of polylactide/montmorillonite nanocomposites. In this study, the presence of glycerol seems to influence the nanocomposites’ morphology, influencing the clay exfoliation in some cases, and the mechanical properties. On the other hand, the presence of glycerol seems to induce a greater molecular weight reduction during twin screw extrusion.

Effect of cationic polyacrylamides on the aggregation and SERS performance of gold nanoparticles-treated paper

This study examines and quantifies the effect of cationic polyelectrolyte adsorption on paper on the aggregation and retention of gold nanoparticles (AuNPs) to optimize their Surface Enhanced Raman Scattering (SERS) enhancement factor and sensitivity. Aggregation of metallic nanoparticles is known as a key factor for intense SERS enhancement. Paper substrates were treated with aqueous solutions of cationic polyacrylamide (CPAM) varying in concentration, charge density, and molecular weight to control the AuNPs’ aggregate size distribution and surface coverage on paper. The Raman Enhancement Factor of AuNPs-CPAM paper was almost an order of magnitude greater than for the untreated AuNPs paper. The high loading and uniform distribution of AuNPs aggregates on CPAM pre-treated paper contributed toward the excellent SERS reproducibility, sensitivity, and high enhancement factor. This configuration of AuNP on paper was favoured by treating the substrate with CPAM solutions of higher concentrations, higher charge density, and greater molecular weight.

Recent Developments in Atom Transfer Radical Polymerization (ATRP): Methods to Reduce Metal Catalyst Concentrations

Atom transfer radical polymerization (ATRP) was initially developed in the mid-1990s, and with continued refinement and use has led to significant discoveries in new materials. However, metal contamination of the polymer product is an issue that has proven detrimental to widespread industrial application of ATRP. The laboratories of K. Matyjaszewski have made significant progress towards removing this impediment, leading the development of "activators regenerated by electron transfer" ATRP (ARGET ATRP) and electrochemically mediated ATRP (eATRP) technologies. These variants of ATRP allow polymers to be produced with great molecular weight and functionality control but at significantly reduced catalyst concentrations, typically at parts per million levels. This Concept examines these polymerizations in terms of their mechanism and outcomes, and is aimed at giving the reader an overview of recent developments in the field of ATRP.

Development of an experimental technique for testing rheological properties of ultrathin polymer films used in nanoimprint lithography

A new method for the measurement of rheological properties (complex viscosity, viscosity and elasticity) of thin polymeric films is presented. The probe, which is placed on the end of an arm of a mini tuning fork, is caused to oscillate and then is put into poly(methyl methacrylate) films, whose thickness ranges from 30 nm to 1080 nm. All measured properties depend on temperature, thickness of the films, indentation depth and the molecular weight of PMMA. Complex viscosity, viscosity and elasticity are found to be lower at higher temperatures and higher with greater molecular weight. They are also lower for thicker films. The results gained from this experiment may be useful in the development of nanoimprint lithography and many other branches of nanotechnology. Furthermore, the method allows for the measurement of the rheological properties of many different thin films (nanoimprint polymers, oils, lubricants) at different temperatures.

Synthesis of fluorene- and anthracene-based π-conjugated polymers and dependence of emission range and luminous efficiency on molecular weight

In the present work poly[9,9-dioctylfluorene-co-2-pentyl-9,10-bis(4-vinylphenyl)anthracene], a fluorene- and anthracene-based copolymer, is synthesized through a Heck coupling reaction. In order to synthesize polymers with high-molecular weight, DMF (P1), DMF/p-Xylene = 1/1 (P2), p-Xylene (P3), and 1,4-Dioxane (P4) are used as solvents, which are an important factor in the synthesis process. The number of average molecular weights ( M n) of the synthesized polymers P1–P4 do not differ significantly, standing at 22,309, 12,369, 29,192, and 39,464, respectively, while their weight average molecular weights ( M w) show considerable differences (i.e. 50,055; 24,042; 125,406; and 231,053). Polymers P1–P4 demonstrate little difference in the results of a thermal analysis, electrochemical analysis, UV–vis analysis, and photoluminescence (PL) spectrum measurement. With regard to electroluminescence (EL) spectrum measurement, however, P1 and P2 show main luminous peaks at 508 nm, while P3 and P4's luminous peaks are seen at 516 nm. Moreover, luminous shoulder peaks were red-shifted with increase of molecular weight of polymers from 460 to 544 nm. In this process, the luminous area is red-shifted from greenish-blue to yellowish-green. The I– V– L measurement results show that the maximum brightness of P1, P2, and P3 ranges from 164 to 303 cd/m 2 and their luminous efficiency is low at 0.031–0.054 cd/A. Meanwhile, the turn-on voltage of P4, having greater molecular weight, is 9.5 V, and its maximum brightness and corresponding luminous efficiency are 736 cd/m 2 and 0.08 cd/A, respectively, implying that the luminous efficiency of devices improves as the molecular weight becomes greater.

Polychlorinated biphenyl behavior in soils amended with biosolids

Assessment of the mobility of polychlorinated biphenyls (PCBs) in soils, amended with biosolids at a rate of 30 Mg ha −1, was performed using an incubation process and leaching columns. The incubation process was carried out for 0, 30, and 60 d under field capacity conditions at 25 °C. The mobility of PCBs was assessed using solutions of 0.5 mol L −1 CaCl 2 and 25 mg L −1 linear alkylbenzenes sulfonate (LAS). Ultrasound-assisted pressurized solvent extraction (US-PSE) was utilized for compound separation from the solid matrix. Compounds were determined by gas chromatography coupled to mass spectrometry. The biosolids, containing a background PCB concentration about 300 μg kg −1, were spiked with the analytes at 300 mg kg −1 to obtain a clearer determination of their behavior when the biosolid was mixed with soil. In biosolid-amended soils, an increase was observed in the extractability of PCBs with increasing incubation time, which may be attributed to organic matter breakdown. The leaching column study showed that CaCl 2 was unable to mobilize the PCBs from the biosolid to the soil, whereas LAS mobilized these compounds within the time scale implicit in the experiment (30 d). The most mobilized congeners in the columns corresponded to those with the greatest molecular weight (hexa- and heptachlorinated), probably due to the higher hydrophobicity of these compounds. Results indicate that the presence of important concentrations of LAS in biosolids could mobilize PCBs from soil to the freatic level.

Synthesis of linear low density polyethylene with a nano-sized silica supported Cp2ZrCl2/MAO catalyst

A nano-sized silica supported Cp2ZrCl2/MAO catalyst was used to catalyze the copolymerization of ethylene/1-hexene and ethylene/1-octene to produce linear low-density polyethylene (LLDPE) in a batch reactor. Under identical reaction conditions, the nano-sized catalyst exhibited significantly higher polymerization activity, and produced copolymer with greater molecular weight and smaller polydispersity index than a corresponding micro-sized catalyst, which was ascribed to the much lower internal diffusion resistance of the nano-sized catalyst. Copolymer density decreased with the increase of polymerization temperature, probably due to the decrease of reactivity ratio r1 and ethylene solubility with increasing temperature. Polymerization activity of the nano-sized catalyst increased rapidly with increasing comonomer concentration. Ethylene/1-octene exhibited higher polymerization activity and had a stronger comonomer effect than ethylene/1-hexene.