Viscosity Average Molecular Mass Research Articles

Energy of Salt Formation and Supramolecular Ordering of Chitosan L- and D-Ascorbates

Using two samples of chitosan (D-glucan) with viscosity-average molecular mass 40 × 103 and 200 × 103 as the example, the influence of diastereomer form (L- and D-) of ascorbic acid on the energetics of formation, structure, and supramolecular ordering of hetero- (D‒L) and homochiral (D‒D) polymer–acid salt complexes has been studied. It has been found that heat effect during the interaction of chitosan with L-ascorbic acid in aqueous medium and degree of protonation of the (D‒L)-salts are lower in comparison with D-isomer of the acid. The homochiral (D‒D)-salts, in contrast to the heterochiral (D‒L)-salts, have exhibited lower amount of crystallization water, high degree of crystallinity, and denser supramolecular structure with high level of inter- and intramolecular contacts.

COMPARATIVE STUDY OF INDUSTRIAL LIGNOSULFONATES AND SOME THEIR PROPERTIES

The aim was to compare the chemical composition and some properties of three industrial lignosulfonates produced as a by-product at three pulp and paper mills (Russia). Using the classical methods of lignin chemistry, it was found that there were differences in the elemental composition and the content of functional groups of the industrial lignosulfonates, but in general, they were not very significant. The Kondopoga lignosulfonates contained the highest content of methoxy, aliphatic hydroxyl groups and carbonyl groups. The Vyborg lignosulfonates had the highest degree of sulfonation and the lowest content of carbonyl groups. The content of the functional groups in the chemical composition of the Syassky lignosulfonates was intermediate between the functional composition of the Vyborg and Kondopoga lignosulfonates. The Vyborg lignosulfonates had the lowest values of the viscosity average molecular mass, dynamic viscosity and surface tension at the air-water interface in comparison with these parameters of the Kondopoga and Syassky lignosulfonates.

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 effect of melt flow index, melt flow rate, and particle size on the thermal degradation of commercial high density polyethylene powder

The powder of EX5 grade of high density polyethylene—without any additives—manufactured by Amirkabir petrochemical company was separated by shaker equipment. The separated powder of average diameter ~25, ~62.5, ~87.5, ~112.5, ~137.5, ~175 and the particles >200 μm was tested by a thermogravimetric (TG) analysis instrument in nitrogen atmosphere and heating rates of 10, 20, and 30 °C min−1. In addition, the separated powders were analyzed by a melt flow index (MFI) instrument, and the viscosity average molecular mass (Mv) of the powders was tested by a viscometer. Kinetic evaluations were performed by Friedman and Kissinger analysis methods and apparent activation energy for the overall degradation of the powders was determined. The effects of molecular mass, MFI, MFR, and particle size on the degradation TG curve, derivative thermogravimetry curve breadth, and activation energy of thermal degradation were considered. The results showed that the Mv of EX5 pipe grade produced by two serial reactors is increased by increasing of the particle size and, MFI is decreased with a little deviation by particle size increasing. The particle size has no obvious effect on the melt flow rate (MFR), and MFR as function of molecular mass distribution does not change very much. The results showed that the powder with bigger particles and higher molecular mass moderately increases the activation energy and shifts the degradation curve to the higher temperatures.

Novel High-Viscosity Polyacrylamidated Chitosan for Neural Tissue Engineering: Fabrication of Anisotropic Neurodurable Scaffold via Molecular Disposition of Persulfate-Mediated Polymer Slicing and Complexation

Macroporous polyacrylamide-grafted-chitosan scaffolds for neural tissue engineering were fabricated with varied synthetic and viscosity profiles. A novel approach and mechanism was utilized for polyacrylamide grafting onto chitosan using potassium persulfate (KPS) mediated degradation of both polymers under a thermally controlled environment. Commercially available high molecular mass polyacrylamide was used instead of the acrylamide monomer for graft copolymerization. This grafting strategy yielded an enhanced grafting efficiency (GE = 92%), grafting ratio (GR = 263%), intrinsic viscosity (IV = 5.231 dL/g) and viscometric average molecular mass (MW = 1.63 × 106 Da) compared with known acrylamide that has a GE = 83%, GR = 178%, IV = 3.901 dL/g and MW = 1.22 × 106 Da. Image processing analysis of SEM images of the newly grafted neurodurable scaffold was undertaken based on the polymer-pore threshold. Attenuated Total Reflectance-FTIR spectral analyses in conjugation with DSC were used for the characterization and comparison of the newly grafted copolymers. Static Lattice Atomistic Simulations were employed to investigate and elucidate the copolymeric assembly and reaction mechanism by exploring the spatial disposition of chitosan and polyacrylamide with respect to the reactional profile of potassium persulfate. Interestingly, potassium persulfate, a peroxide, was found to play a dual role initially degrading the polymers—“polymer slicing”—thereby initiating the formation of free radicals and subsequently leading to synthesis of the high molecular mass polyacrylamide-grafted-chitosan (PAAm-g-CHT)—“polymer complexation”. Furthermore, the applicability of the uniquely grafted scaffold for neural tissue engineering was evaluated via PC12 neuronal cell seeding. The novel PAAm-g-CHT exhibited superior neurocompatibility in terms of cell infiltration owing to the anisotropic porous architecture, high molecular mass mediated robustness, superior hydrophilicity as well as surface charge due to the acrylic chains. Additionally, these results suggested that the porous PAAm-g-CHT scaffold may act as a potential neural cell carrier.

Rheological characterization of the galactomannan from Leucaena leucocephala seed

A water soluble galactomannan isolated from Leucaena leucocephala seeds gave an intrinsic viscosity of 3.5dl/g and viscosity average molecular mass, Mv, of 6.98×105g/mol. This was in reasonably good agreement with the value of the weight average molecular mass, Mw, of 5.44±0.20×105g/mol determined by GPC-MALLS coupled to RI. The onset of polymer coil overlap occurred at c*[η] of 2.1, with slope of 3.0 above and 1.3 below the point of polymer coil overlap. The shear viscosity of the polysaccharide was temperature dependent and decreased with increasing temperature. The activation energy for viscous flow of 3.0% polysaccharide concentration obtained by Arrhenius plot of zero shear viscosity as a function of temperature was 26.4kJ/mol. Both the storage modulus (G′) and loss modulus (G″) showed strong dependence on frequency indicating the presence of entangled coils. The Cox–Merz plot gave close superimposition of the complex and shear viscosities.

Cryopolymerization of N,N-dimethylacrylamide in moderately frozen formamide

The free-radical polymerization of N,N-dimethylacrylamide initiated by the redox pair ammonium persulfate-N,N,N′,N′-tetramethylethylenediamine in moderately frozen and liquid formamides is studied at temperatures 10–30°C below or above the temperature of crystallization (2.9°C) of the pure solvent at various monomer concentrations in the initial solution. When polymerization is conducted at temperatures below the temperature of crystallization of formamide, the frozen systems, as is evident from their phase diagrams, include the crystallized main bulk of the solvent and the noncrystallizing monomer concentrated in the unfrozen liquid microphase where the reaction occurs. It is found that, in the case of this cryopolymerization variant, the temperature dependences of the yield of the polymer and its viscosity-average molecular mass show an extremum pattern and the positions of maximum points relative to the temperature scale depend on the initial monomer concentration. It is shown that the molecular masses of cryopolymerization products are much higher and their molecular-mass distribution is wider than that of poly(N,N-dimethylacrylamide) samples synthesized through solution polymerization (above the temperature of crystallization of formamide) at the same concentration of the monomer.

Agarose and polyacrylamide gel electrophoresis methods for molecular mass analysis of 5- to 500-kDa hyaluronan

Agarose and polyacrylamide gel electrophoresis systems for the molecular mass-dependent separation of hyaluronan (HA) in the size range of approximately 5–500kDa were investigated. For agarose-based systems, the suitability of different agarose types, agarose concentrations, and buffer systems was determined. Using chemoenzymatically synthesized HA standards of low polydispersity, the molecular mass range was determined for each gel composition over which the relationship between HA mobility and logarithm of the molecular mass was linear. Excellent linear calibration was obtained for HA molecular mass as low as approximately 9kDa in agarose gels. For higher resolution separation, and for extension to molecular masses as low as approximately 5kDa, gradient polyacrylamide gels were superior. Densitometric scanning of stained gels allowed analysis of the range of molecular masses present in a sample as well as calculation of weight-average and number-average values. The methods were validated for polydisperse HA samples with viscosity-average molecular masses of 112, 59, 37, and 22kDa at sample loads of 0.5μg (for polyacrylamide) to 2.5μg (for agarose). Use of the methods for electrophoretic mobility shift assays was demonstrated for binding of the HA-binding region of aggrecan (recombinant human aggrecan G1–IGD–G2 domains) to a 150-kDa HA standard.

Rheological behaviour of tamarind seed gum in aqueous solutions

Tamarind seed gum as seed polysaccharide from Tamarindus indica L. has been characterized for physicochemical and rheological properties in the present work. The structural analysis determined the presence of glucose:xylose:galactose in a molar ratio of 2.61:1.43:1.The Huggins and Kraemer plots obtained by capillary viscometry gave an intrinsic viscosity of 4.7 dl g −1 and the viscosity average molecular mass was calculated to be 9.18 × 10 5 g mol −1 using the Mark–Houwink relationship. The steady shear and dynamic viscoelasticity properties of tamarind seed gum in aqueous solutions at different concentrations were investigated at 20 °C using a Haake Rheometer RS75. The tamarind seed gum solutions clearly exhibited shear-thinning flow behaviour at high shear rate and Newtonian region occurred at low shear rate range, however, at higher concentrations, pronounced shear thinning was observed. The value of zero shear viscosity ( η 0) was estimated by fitting Cross and Carreau models. The specific viscosity at zero shear rate ( η sp 0) was plotted against the coil overlap parameter ( C[ η]) and the slopes of the lines in the dilute and semi-dilute regions were found to be ∼2.2 and 4.3, respectively. The value of the critical concentration ( C ∗) was about 4.23/[ η]. While, the mechanical spectra in the linear viscoelastic region of tamarind seed gum solutions showed the typical shape for macromolecular solutions. Plots of η versus γ and η ∗ versus ω were superimposable and hence obey the Cox–Merz rule.

Production and characterization of PHB from two novel strains of Bacillus spp. isolated from soil and activated sludge

The present study reports two bacteria, designated 87I and 112A, which were isolated from soil and activated sludge samples from Hyderabad, India, and that are capable of producing poly-3-hydroxybutyrate (PHB). Based on phenotypical features and genotypic investigations, these microorganisms were identified as Bacillus spp. Their optimal growth occurred between 28 degrees C and 30 degrees C and pH 7. Bacillus sp. 87I yielded a maximum of 70.04% dry cell weight (DCW) PHB in medium containing glucose as carbon source, followed by 55.5% DCW PHB in lactose-containing medium, whereas Bacillus sp. 112A produced a maximum of 67.73% PHB from glucose, 58.5% PHB from sucrose, followed by 50.5% PHB from starch as carbon substrates. The viscosity average molecular mass (M (v)) of the polymers from Bacillus sp. 87I was 513 kDa and from Bacillus sp. 112A was 521 kDa. All the properties of the biopolymers produced by the two strains 87I and 112A were characterized.

A novel Bacillus sp. accumulating poly (3-hydroxybutyrate-co-3-hydroxyvalerate) from a single carbon substrate

The objective of this paper was to report a bacterium designated as 88D, capable of producing poly (3-hydroxybutyrate-co-3-hydroxyvalerate) [P (3HB-co-3HV)] copolymer from a single carbon source, which was isolated from a municipal sewage treatment plant in Hyderabad, India. This microorganism, based on the phenotypical features and genotypic investigations, was identified as Bacillus sp. The optimal growth of Bacillus sp. 88D occurred between 28 and 30 degrees C and at pH 7. The strain yielded a maximum of 64.62% dry cell weight (DCW) polymer in the medium containing glucose as carbon source, which was followed by 60.46% DCW polymer in glycerol containing medium. Bacillus sp. 88D produced P (3HB-co-3HV) from glucose or glycerol, when they were used as a single carbon substrate. This bacterium produced polyhydrxybutyrate (PHB) when sodium acetate was used as sole carbon substrate. The viscosity average molecular mass (Mv) of the copolymers ranged from 523 to 627 kDa. The physical, chemical and mechanical properties of the biopolymers were characterized.

Isolation and rheological characterization of Mucuna flagellipes seed gum

The gum from Mucuna flagellipes seed endosperm has been isolated and characterised using capillary viscometry and steady shear and small deformation oscillatory rheometry. The endosperm was found to constitute 67.15% of the whole seed and yielded 32.6% of gum. The Huggins and Kraemer plots obtained by capillary viscometry gave an intrinsic viscosity of 7.9 dL/g and viscosity average molecular mass was calculated to be 2.1 × 10 6 using the Mark–Houwink relationship. The zero shear viscosity was plotted against the coil overlap parameter, C[ η], and the slopes of the lines in the dilute and semi-dilute regions were found to be ∼1.0 and 4.6 respectively. The curves were fitted to the Tuinier and Martin equations and showed only qualitative agreement. The shear flow viscosity profiles indicated that M. flagellipes gum did not exhibit significant shear thinning at polymer concentrations less than 0.5%, however, at higher concentrations, pronounced shear thinning was observed with the relaxation time ( τ) increasing with increase in polymer concentration. The dynamic viscosity profiles showed that at all polymer concentrations examined, a Newtonian plateau was obtained at low frequencies indicating that the loss modulus was the dominant response. Plots of log η versus log γ ˙ and log η ∗ versus log ω were not superimposible and hence did not obey the Cox–Merz rule.

Viscous-flow properties and viscosity-average molecular mass of orange peel pectin

The viscous-flow properties of pectin from the residue of orange peel after extraction of essential oil and flavonoid were studied and the viscosity-average molecular mass (Mv, ave) of this kind of pectin was determined. Experimental results show that Arrhenius viscous-flow equation can be applied to describing the effect of temperature on viscosity of this kind of orange peel pectin solutions with the average viscous-flow activation energy being 17.91 kJ/mol (depending on the concentration). Neither power equation, \( \eta = K_1 c^{A_1 } \), or exponential equation, η=K2exp(A2c) can describe the effect of concentration on viscosity of this kind of orange peel pectin solutions well. However, it seems that exponential equation model is more suitable to describe their relation due to its higher linear correlation coefficient. Schulz-Blaschke equation can be used to calculate the intrinsic viscosity of this kind of orange peel pectin. The Mv, ave of the orange peel pectin is 1.65×105 g/mol.

Extraction, purification and characterization of galactomannans from non-traditional sources

This work presents a methodology for the extraction of galactomannans from seeds of four different species of Leguminosae ( Adenanthera pavonina, Caesalpinia pulcherrima, Gleditsia triacanthos and Sophora japonica) to be used e.g. in the food and biomedical industries. The galactomannans were obtained by aqueous extraction followed by a precipitation with ethanol. This methodology is simpler and easier to perform than other existing extraction and purification methodologies, and because it avoids the use of organic solvents (other than ethanol), it is able to generate food grade substances and is environmentally friendlier. The yield of extraction in different stages of the process, monosaccharide composition, as well as physical and chemical parameters of the isolated galactomannans were determined and compared with previously published results. The mannose/galactose ratio of the extracted galactomannans ranged from 1.35 ( A. pavonina) to 5.75 ( S. japonica). The intrinsic viscosity ranged from 11.34 dL/g ( C. pulcherrima) to 8.74 dL/g ( S. japonica), while the viscosity average molecular mass ranged between 1.81 × 10 6 Da and 1.17 × 10 6 Da ( A. pavonina > C. pulcherrima > G. triacanthos > S. japonica). The results confirm the suitability of the extraction and purification procedure to obtain galactomannans from non-traditional sources.

A Comparative Study of Preparation of Porous Poly‐L‐lactide Scaffolds Using NaHCO3 and NaCl as Porogen Materials

Poly‐l‐lactide (PLLA) scaffold materials were fabricated by using NaCO3 and NaCl as porogens, and the influences of porogen on the properties of the scaffold were investigated. The scaffold fabricated with NaHCO3 as porogen is more highly porous and has more macropores than that fabricated with NaCl. As a porogen, NaHCO3 particulate is easier to leach out than NaCl, due to quickly reacting with HCl solution and producing CO2. Distilled water soaking treatment has little effect on the viscosity average molecular mass of PLLA; however, HCl solution treatment decreases the viscosity average molecular mass of PLLA. The PLLA scaffold fabricated with NaHCO3 has a lower compressive strength than that fabricated with NaCl.

Synthesis of Poly-L-Lactide for Scaffold Materials by Melt-Solid Polycondensation

Poly-L-lactide (PLLA) with low viscosity average molecular mass for scaffold materials was synthesized by melt-solid condensation polymerization and characterized by IR, XRD, and 1H-NMR. The influences of catalyst (LaCl3/C7H8SO3) concentration, polymerization temperature and polymerization time on the viscosity average molecular mass of poly-L-lactide acid (PLLA) were investigated. Poly-L-lactide with a viscosity average relative molecular mass of about 7.2 × 104 was obtained when melt-solid polycondensation was conducted with first preheating at 110°C for 4 h and solid polycondensation at 150°C for 20 h; the catalyst concentration was 0.4 wt. %. PLLA was made into porous materials by using sodium hydrogen carbonate particulates as the porogen to foam. Scanning electron microscope observation indicates that the sample is highly porous and well distributed with good interconnections between pores and the pore size of porous materials in the range of 300–500 μm and it can be used as scaffold for bone tissue engineering.

Effects of novel quasi‐interpenetrating network/gold nanoparticles composite matrices on DNA sequencing performances by CE

Gold nanoparticles (GNPs) with particle sizes of about 20, 40, and 60 nm were prepared and added into a quasi-interpenetrating network (quasi-IPN) composed of linear polyacrylamide (LPA) with different viscosity-average molecular masses of 1.5, 3.3, and 6.5 MDa and poly-N,N-dimethylacrylamide (PDMA) to form polymer/metal composite matrices, respectively. These novel matrices could improve ssDNA sequencing performances due to interactions between GNPs and polymer chains and the formation of physical cross-linking points as demonstrated by intrinsic viscosities and glass transition temperatures. The effects of the parameters in relation to quasi-IPN/GNPs matrices, such as GNP contents, GNP particle sizes, LPA molecular masses, and solution concentrations, on ssDNA sequencing performances were studied. In the presence of GNPs, the separation had the advantages of high resolution, speediness, excellent reproducibility, long shelf life and easy automation. Therefore, less viscous matrix solutions (with moderate size GNPs) due to lower solution concentration and lower-molecular-mass LPA could be used to replace more viscous solutions (without GNPs) due to higher solution concentration or higher-molecular-mass LPA to separate DNA, while the sieving performances were approximate even higher, which helped to achieve full automation especial for capillary array electrophoresis (CAE) and microchip electrophoresis (MCE).

Novel quasi‐interpenetrating network/gold nanoparticles composite matrices for DNA sequencing by CE

In order to further improve ssDNA sequencing performances using quasi-interpenetrating network (quasi-IPN) as a matrix composed of linear polyacrylamide (LPA) with lower viscosity-average molecular mass (3.3 MDa) and poly(N,N-dimethylacrylamide) (PDMA), gold nanoparticles (GNPs) were prepared and added into this quasi-IPN to form polymer/metal composite sieving matrices. The studies of intrinsic viscosity and differential scanning calorimetry (DSC) on quasi-IPN and quasi-IPN/GNPs indicate that there were interactions between GNPs and polymer chains. The sequencing performances on ssDNA using quasi-IPN and quasi-IPN/GNPs (with different GNPs concentrations) as sieving matrices were studied and compared by CE at different temperatures. The results show that resolutions of quasi-IPN/GNPs were higher than those of quasi-IPN without GNPs and approximated those of quasi-IPN composed of LPA with higher MW (6.5 MDa) and PDMA without GNPs in the bare fused-silica capillaries. Furthermore, the sequencing time of quasi-IPN/GNPs was shorter than that of quasi-IPN under the same sequencing conditions. The influences of GNPs and sequencing temperature on the sequencing performances of ssDNA were also discussed. The separation reproducibility of quasi-IPN/GNPs solution was excellent and its shelf life was more than 8 months.

Preparation of high viscosity average molecular mass poly-L-lactide

Poly-L-lactide(PLLA) was synthesized by ring-opening polymerization from high purity L-lactide with tin octoate as initiator, and characterized by means of infrared, and 1H-nuclear magnetic resonance. The influences of initiator concentration, polymerization temperature and polymerization time on the viscosity average molecular mass of PLLA were investigated. The effects of different purification methods on the concentration of initiator and viscosity average molecular mass were also studied. PLLA with a viscosity average molecular mass of about 50.5×104 was obtained when polymerization was conducted for 24 h at 140 °C with the molar ratio of monomer to purification initator being 12 000. After purification, the concentration of tin octoate decreases; however, the effect of different purification methods on the viscosity average molecular mass of PLLA is different, and the obtained PLLA is a typical amorphous polymeric material. The crystallinity of PLLA decreases with the increase of viscosity average molecular mass.

Synthesis and Characterization of Novel Polymeric-Schiff Bases and Their Complexes

An investigation of the solid state conductivity of polymeric-Schiff bases derived from the condensation reaction of polyacrylamide and an aldehyde (4-methoxybenzaldehyde and 4-chlorbenzaldehyde) has been carried out and Co(II) and Ni(II) complexes have been prepared. Polymeric-Schiff bases and their metal complexes were characterized by molar conductance, magnetic susceptibility, and electronic and IR spectral studies. Conductivity measurements were carried out at 20 °C in dimethylformamide to determine the electrolytic behavior. The 1H-NMR and 13C-NMR spectra, elemental analysis, and viscosity average molecular mass (M v) of the polymeric-Schiff bases and their complexes were determined. All of the polymer–metal complexes showed high thermally stability. The DC conductivities of the solid samples were measured using a four-probe technique.