Influence Of Molar Mass Research Articles

Influence of Molar Mass and Degree of Substitution on Water Solubility of DEAE-Functionalized Apple Glycans

Influence of Molar Mass and Degree of Substitution on Water Solubility of DEAE-Functionalized Apple Glycans

Hybrid polymer/lipid vesicles: Influence of polymer architecture and molar mass on line tension

Hybrid polymer/lipid vesicles are self-assembled structures that have been the subject of an increasing number of studies in recent years. They are particularly promising tools in the development of cell membrane models because they offer the possibility to fine-tune their membrane structure by adjusting the distribution of components (presence or absence of “raft-like” lipid domains), which is of prime importance to control their membrane properties. Line tension in multiphase membranes is known to be a key parameter on membrane structuration, but remains unexplored, either experimentally or by computer modeling for hybrid polymer/lipid vesicles. In this study, we were able to measure the line tension on different budded hybrid vesicles, using a micropipette aspiration technique, and show the influence of the molar mass and the architecture of block copolymers on line tension and its consequences for membrane structuration.

Extraction and purification of Aspergillus tamarii β-fructofuranosidase with transfructosylating activity using aqueous biphasic systems (PEG/phosphate) and magnetic field

β-fructofuranosidases (FFases) are enzymes involved in sucrose hydrolysis and fructo-oligosaccharides’ production which are of great interest for the food industry. FFase from Aspergillus tamarii URM4634 was extracted using PEG/Phosphate Aqueous Biphasic Systems (ABS), and the impact of magnetic field on the extraction behavior was evaluated. A 24-full experimental design was employed to study the influence of molar mass of PEG, concentrations of PEG and phosphate and pH on the selected response variables, i.e., partition coefficient (K), purification factor (PF), activity yield (Y) and selectivity (S). The influence of magnetic field during partition and NaCl concentration on the same responses was also studied. The best results of FFase extraction without magnetic field (K = 0.50, PF = 4.05, Y = 72.66% and S = 0.06) were observed at pH 8.0 using 12.5% (w/w) PEG 400 and 25% (w/w) NaH2PO4/K2HPO4. Application of the magnetic field allowed improving the performance, with the best results being obtained at the longest distance between magnets (lowest magnetic field) and absence of NaCl (K = 0.93, PF = 4.22, Y = 83.79% and S = 0.09). The outcomes obtained demonstrate that ABS combination with low intensity magnetic field can be used as an efficient FFase pre-purification method.

Adsorption Kinetics of cis-1,4-Polyisoprene in Nanopores by In Situ Nanodielectric Spectroscopy

Using in situ nanodielectric spectroscopy, we studied the adsorption kinetics of cis-1,4-polyisoprene (PI) into porous alumina by following the evolution of the dielectrically active longest normal mode. We studied the influence of molar mass, nanopore diameter, and surface functionalization. Adsorption times depend strongly on the ratio 2Rg/D, where Rg is the radius is gyration and D is the pore diameter. For a given pore diameter, the characteristic adsorption times are some 8 orders of magnitude slower than the terminal relaxation times and more than 12 orders of magnitude slower than the segmental times. The extremely slow kinetics reflect the fact that exchanging chains with the pore surface have to pass through several unfavorable configurations (e.g., trains, loops). The molar mass dependence of the characteristic adsorption times (τads ∼ N2.6) is in good agreement with a scaling theory proposed by de Gennes and later refined by Semenov and Joanny. Subsequently, we investigated the imbibition of miscible PI blends by taking advantage of the difference in imbibition speeds of the respective homopolymers. We show that the shorter chains penetrate first the nanopores, whereas the longer chains enter only at the late stages of the filling process. Moreover, the long-time adsorption is dominated by an exchange mechanism involving primarily the shorter chains. The results from in situ nanodielectric spectroscopy demonstrate the capacity of the technique to provide the imbibition length, the adsorption kinetics, and, at the same time, the chain dynamics.

Rheological Measurements and Structural Analysis of Polymeric Materials.

Rheological measurements of polymer melts are widely used for quality control and the optimization of processing. Another interesting field of rheology is to provide information about molecular parameters of polymers and the structure build-up in heterogeneous polymeric systems. This paper gives an overview of the influence of molar mass, molar mass distribution and long-chain branching on various rheological characteristics and describes the analytical power following from established relations. With respect to applications, we discuss how rheological measurements can be used to gain insight into the thermal stability of a material. A special impact lies in the demonstration, how long-chain branching can be analyzed using rheological means like the zero-shear viscosity as a function of molar mass and strain hardening occurring in elongation. For contributions to branching analysis, the thermorheological behavior and activation energies are particularly discussed. The use of elastic quantities in the case of mechanical pretreatment effects is briefly addressed. The influence of fillers on recoverable properties in the linear range of deformation is analyzed and the role of their specific surface area for interactions described. It is shown how the fundamental results can be applied to study the state of nanoparticle dispersions obtained under special conditions. Furthermore, it is demonstrated that the findings on polymer/filler systems are the base of structure analyses in heterogeneous polymeric materials like polyvinylchloride (PVC) and acrylonitrile–butadiene–styrene copolymers (ABS).

Phase diagram of P3HT:PC70BM thin films based on variable-temperature spectroscopic ellipsometry

In this article, we present the research on the influence of the composition of thin films of a blend of poly (3-hexylthiophene −2,5-diyl) - P3HT with fullerene derivatives [6,6]-phenyl-C71-butyric acid methyl ester – PC70BM and [6,6]-phenyl-C61-butyric acid methyl ester – PC60BM on their thermal transitions. The influence of molar mass (Mw) of P3HT (Mw = 65.2; 54.2 and 34.1 kDa) and PCBM (PC60BM – Mw = 911 g/mol and PC70BM – Mw = 1031 g/mol) is examined in details. The article presents significantly expanded research compared to our previous work on thermal transitions in thin films of blend P3HT (Mw = 65.2 kDa) with PC60BM. For this reason, we also compare current results with previous ones. Here, we present for the first time a phase diagram of thin films of the P3HT(Mw = 65.2 kDa):PC70BM blend using variable-temperature ellipsometry. Our research reveals the presence of characteristic temperatures of pure phases in thin films of P3HT: PCBM blends. It turns out that the cold crystallization temperature of the P3HT phase in P3HT(Mw = 65.2 kDa):PC70BM blend films is lower than corresponding temperature in P3HT(Mw = 65.2 kDa):PC60BM blend films. At the same time, the cold crystallization temperature of the PC70BM phase behaves inversely. We demonstrate also that variable-temperature spectroscopic ellipsometry is a very sensitive technique for studying thermal transitions in these thin films. In addition, we show that the entire phase diagram can be determined based on the raw ellipsometric data analysis, e.g. using a delta angle at wavelength λ = 280 nm.

Influence of molar mass of partially hydrolyzed polyacrylamide on the treatment of produced water from enhanced oil recovery

Enhanced oil recovery (EOR) generates a large amount of produced water with emulsified oil, that must be treated before its final disposition. Polymer flooding is a chemical EOR method that is used to improve oil production, and these polymers can reportedly hinder the produced water treatment step. Flocculants are used to treat the produced water, and this work proposed to evaluate the EOR produced water treatment and the impact of the EOR polymers molar masses on the oil removal efficiency. For that, partially hydrolyzed polyacrylamide (HPAM) with different molar masses were used as the EOR polymer, while the flocculant used was a Polyethylenimine (PEI), an underexplored flocculant in oil industry. HPAM was evaluated in two concentrations (100 and 1000 ppm), under two different conditions: sheared and non-sheared. Flocculation with PEI was carried out in a Jartest equipment followed by Dissolved air flotation (DAF). The best oil removal results were achieved at 100 ppm concentration of HPAM, under shearing conditions.

Research of Surface-Active Properties of Waste of Processing of Tin Ores

The object of research is the waste of enrichment of ories of the closed mining enterprise “Solnechny GOK” of the Khabarovsk territory of the Far Eastern Federal district. The article discusses the results of research of surface-active properties of waste of enrichment of tin ories due to their impact on the environment and public health. Sodium oxalate, trilon B, methylene blue, sodium humate were used as sorbates. Methods for the determination of interaction of waste with the sorbates – thermal effect and discoloration of colored complexing agents in the presence of the waste. Titrimetric methods were used to determine the number of reaction centers of waste. For to determine the nature of the active centers of wastes was use the extinguish of the foam generated by the anionic and nonionic surfactants. The influence of molar mass and structure of sorbates on the nature of their interaction with the waste surface is shown. High molecular polydentate complexing agent form a surface film. Low molecular weight sorbates contribute to the formation of soluble complexes of heavy metals and pollution of water systems. The revealed physico-chemical properties will allow to predict the increase in the probability of groundwater contamination by low molecular weight organic complexing agents and also probability of the best fixing of soils on waste in the presence of high-molecular organic substances of soil absorption complex.

Molecular structure influence on bending behavior of polyester filaments examined using a modified cantilever bending test

ABSTRACTAn experimental setup used to measure the bending stiffness of polymer filaments based on existing cantilever approaches is presented. Additionally, it is utilized to evaluate the influence of molar mass and long‐chain branching on filaments of poly(butylene terephthalate), modified with a multifunctional chain extender. Using shear rheological analysis process limits for extrusion of the modified material were revealed, indicated by a change of the curve shape of van Gurp–Palmen plots. For the processable modified materials, it was found that increasing molar mass and degree of long‐chain branching, caused by the modification, raise the bending stiffness of filaments. Also the Young's modulus was found to increase with the amount of chain extender used, while no difference could be generated by using different linear molar grades of the polymer. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47952.

Molar mass and temperature dependence of rheological properties of polymethylmethacrylate melt

The influence of molar mass and temperature on the rheological properties of polymethylmethacrylate (PMMA) melts was investigated by dynamical mechanical and creep-recovery experiments. The results shown that the steady state viscosities obtained from both experimental modes were in good agreement, and a well linear relationship between the activation energy and molar mass was obtained. The creep compliance of PMMA increased with the molar mass increased or temperature decreased, while the linear steady state recoverable compliance was found to be independent of the molar mass and temperature. Moreover, it was found that the master curves followed the time-temperature superposition principle well in the whole frequency range or time scale.

Influence of molar mass, dispersity, and type and location of hydrophobic side chain moieties on the critical micellar concentration and stability of amphiphilic HPMA-based polymer drug carriers

In the present paper, we address the question to which extent the critical micellar concentration (cmc) value can be varied for clinically related drug delivery carriers if all crucial parameters needed for successful drug delivery are already preset. For this purpose, the cmc values of an amphiphilic polymer carrier based on N-(2-hydroxypropyl) methacrylamide (HPMA) with cholesterol side groups, differing in a variety of parameters, such as molar mass, dispersity, architecture (statistical vs. diblock copolymer), and spacer structure, were studied in detail. At this, we chose physiological conditions (phosphate buffered saline at pH 7.4) and investigated the formation of micelles using fluorescence correlation spectroscopy in dependence on polymer concentration. Moreover, conjugates where the cholesterol moieties are attached to the HPMA backbone by a pH-cleavable hydrazone bond were investigated in dependence on time with respect to their long-term stability at pH 7.4, and it was found that the nanoparticles change size in the course of a few weeks. After a pH change from 7.4 to 5.0 (typical for tumor cells), the nanoparticles grow during the first few hours, then shrink. A weak correlation between the cmc value and the content of the hydrophobic group was found for HPMA-based polymers, regardless their architecture, polydispersity, and spacer structure. A much stronger correlation was observed between the cmc value and the dispersity. This finding could be explained by the higher absolute number of hydrophobic groups located on the higher molar mass fractions of the HPMA copolymers, which initiate the micelle formation.

Influence of molar mass on the thermal properties, conductivity and intermolecular interaction of poly(ethylene oxide) solid polymer electrolytes

AbstractThe sample preparation pathway of solid polymer electrolytes (SPEs) influences their thermal properties, which in turn governs the ionic conductivity of the materials especially for systems consisting of a crystallizable constituent. Majority of poly(ethylene oxide) (PEO)‐based SPEs with molar masses of PEO well above 104 g mol−1 (where PEO is crystallizable and should reach an asymptote in thermal behaviour) display molar mass dependence of the thermal properties and ionic conductivities in non‐equilibrium conditions, as reported in the literature. In this study, PEO of different viscosity‐molar masses (Mη = 3 × 105, 6 × 105, 1 × 106, 4 × 106 g mol−1) and LiClO4 salt (0 to 16.7 wt%) were used. The SPEs were thermally treated under inert atmosphere above the melting temperature of PEO and then cooled down for subsequent isothermal crystallization for sufficient experimental time to develop morphology close to equilibrium conditions. The thermal properties (e.g. glass transition temperature, melting temperature, crystallinity) according to differential scanning calorimetry and the ionic conductivity obtained from impedance spectroscopy at room temperature (σDC ∼ 10−6 S cm−1) demonstrate insignificant variation with respect to the molar mass of PEO at constant salt concentration. These findings are in agreement with the PEO crystalline structures using X‐ray diffraction and ion − dipole interaction by Fourier transform infrared results. © 2017 Society of Chemical Industry

Preparation of Nanocomposites of Polypropylene/Alkylaluminum-modified Clay: Effect of Polymer Grade, Amount of Clay, and Screw Speed

ABSTRACTBentonite was modified with trialkylaluminum to prepare polypropylene/clay nanocomposites. Treated clay, commercial polypropylene, and a coupling agent were mixed in miniextruder. To obtain the masterbatches and dilutions, two polypropylene grades were used to analyze the influence of molar mass on clay dispersion. The screw rotation varied from 30 to 200 rpm, and the clay content was 1, 2, and 5 wt%. For samples prepared with higher molar mass, increasing speed from 30 to 200 rpm improved the clay dispersion. For processing with lower molar mass, decreasing speed from 60 to 30 rpm caused an increase in viscosity, resulting in better dispersion.

High-density polyethylene/needle-like sepiolite clay nanocomposites: effect of functionalized polymers on the dispersion of nanofiller, melt extensional and mechanical properties

Influence of molar mass and polarity of PE-g-MA on different properties [Morphological, Melt extensional, Mechanical and Thermal] of HDPE/sepiolite nanocomposites is reported.

Effect of molar mass on film-forming properties of self-crosslinking latexes based on structured acrylic microgels

Abstract The influence of molar mass of the shell layer of latex particles having core–shell morphology on film-forming and final coating properties of self-crosslinking latexes based on keto-hydrazide crosslinking system was investigated. Structured latex particles were prepared by the semi-continuous non-seeded emulsion polymerization of acrylic monomers. The particle core was slightly crosslinked to prevent the copolymers forming the core phase from migration into the shell phase. The molar mass of copolymers forming the shell phase was gradually reduced by isooctyl 3-mercaptopropionate chain transfer agent included in the synthesis of the shell layers. The results confirmed theoretical predictions and revealed that even a slight amount of chain transfer agent added during the synthesis achieved a substantial lowering of minimum film-forming temperature and reduction of water sensitivity of latex coatings.

Characterization of sodium carboxymethyl cellulose by comprehensive two-dimensional liquid chromatography

Two series of sodium carboxymethyl celluloses (NaCMC) with average degrees of substitution (DS) ranging from 0.45 to 1.55 were synthesized from low molecular mass Avicel cellulose (Avicel samples) and from high molecular mass cotton linters (BWL samples). The samples were characterized by online two-dimensional liquid chromatography using gradient liquid adsorption chromatography in the first and size exclusion chromatography (SEC) in the second dimension. This method allows the simultaneous determination of the chemical composition (DS) and the molar mass distribution within the individual samples. Moreover information was obtained on the dependence of the elution volume in gradient chromatography on molar mass. As expected, evidence for a stronger influence of molar mass on gradient elution volume was found for the low molecular mass NaCMC as compared to the high molecular mass BWL samples. Finally the applicability of the method for the simultaneous separation of blends heterogeneous with respect to chemical composition (DS) and molar mass was demonstrated. Such blends cannot be efficiently separated by either SEC or gradient chromatography alone, nor by simply combining the results of both methods. Only the complete two-dimensional chromatogram can reveal the complexity of such blends, since it reveals the correlations between molar mass and chemical composition.

Influence of Molar Mass and Concentration on the Thermogelation of Methylcelluloses

In this study, thermogelation of methylcelluloses is investigated in relation to the molar mass and concentration in aqueous medium. A large hysteresis between heating and cooling ramps was observed whatever the conditions. The heating process in particular was studied to analyze the two steps of gelation using rheometry. At low temperature, in the sol state, viscosity depends on the concentration and molar mass. Over 30°C a gel-like behavior was observed including two steps (the second step is a strong gel with phase separation) having storage moduli that are nearly independent of polymer molar mass but are directly related to polymer concentration.

Interfacial Properties of Methylcelluloses: The Influence of Molar Mass

The interfacial interactions of four methylcelluloses having the same average degree of substitution and distribution of methyl groups, but different molar masses, are studied at ambient temperature and at very low polymer concentrations. Firstly, the surface tension σ at the water/air interface is determined for the progressive addition of methylcellulose up to 100 mg/L; σ starts to decrease over 1 mg/L up to the critical aggregation concentration (CAC) at 10 mg/L. The curves describing the influence of polymer concentration on σ are independent of the molar mass at equilibrium. Secondly, the adsorption of methylcellulose on silica particles is estimated from ζ-potential measurements. The data are interpreted in terms of an increase of the adsorbed layer thickness at the interface when the molar mass of methylcellulose increases. It is concluded that methylcellulose is adsorbed, forming trains and loops at the interface based on the equilibrium between surface free energy and solvent quality.

Highly efficient hyperbranched CNT surfactants: influence of molar mass and functionalization.

End-group-functionalized hyperbranched polymers were synthesized to act as a carbon nanotube (CNT) surfactant in aqueous solutions. Variation of the percentage of triphenylmethyl (trityl) functionalization and of the molar mass of the hyperbranched polyglycerol (PG) core resulted in the highest measured surfactant efficiency for a 5000 g/mol PG with 5.6% of the available hydroxyl end-groups replaced by trityl functions, as shown by UV-vis measurements. Semiempirical model calculations suggest an even higher efficiency for PG5000 with 2.5% functionalization and maximal molecule specific efficiency in general at low degrees of functionalization. Addition of trityl groups increases the surfactant-nanotube interactions in comparison to unfunctionalized PG because of π-π stacking interactions. However, at higher functionalization degrees mutual interactions between trityl groups come into play, decreasing the surfactant efficiency, while lack of water solubility becomes an issue at very high functionalization degrees. Low molar mass surfactants are less efficient compared to higher molar mass species most likely because the higher bulkiness of the latter allows for a better CNT separation and stabilization. The most efficient surfactant studied allowed dispersing 2.85 mg of CNT in 20 mL with as little as 1 mg of surfactant. These dispersions, remaining stable for at least 2 months, were mainly composed of individual CNTs as revealed by electron microscopy.

The influence of molar mass on rheological and dilute solution properties of poly(butylene succinate)

ABSTRACTThe fundamental rheological properties of a wide molar mass Mw range of poly(butylene succinate)s (PBSs) are investigated. For entangled samples and a reference temperature of 140°C, the shear viscosity is described by the Carreau–Yasuda model. The plateau modulus is estimated at 1.5 × 105 Pa, the average activation energy of PBS melt is , and the critical molar mass for entanglement Mc is found to be 16,000 g mol−1 (PS equivalent). The dilute solution properties of PBS are also studied. A size exclusion chromatography equipped with a triple detection system is used to estimate the Mark–Houwink–Sakurada (MHS) parameters of PBS in solution in chloroform at 30°C. The exponent a and the coefficient K of the MHS relationship are found to be 0.71 ± 0.1 and 39.94 × 10−5 ± 6.31 × 10−5 dL g−1(g mol−1)−a, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40887.