Relative Viscosity Measurements Research Articles

Volumetric and viscometric study of thiamine hydrochloride, pyridoxine hydrochloride and sodium ascorbate at T = (275.15, 277.15 and 279.15) K in dilute aqueous solutions

This paper presents data for density (ρ) and relative viscosity (ηr) measurements of aqueous solutions of thiamine hydrochloride, pyridoxine hydrochloride and sodium-L-ascorbate in dilute solutions (0–0.1) mol·kg−1 at three different temperatures, T=(275.15, 277.15 and 279.15)K and at 101.3kPa. Density results have been used to calculate apparent molar volume of solute (Vϕ), limiting apparent molar volume of solute (Vϕ0), limiting apparent molar expansivity of solute (Eϕ0), (∂2Vϕ0/∂T2) and coefficient of thermal expansion (α∗). Calculated viscosity values have been correlated according to Jones-Dole equation to obtain Falkenhagen coefficient A, Jones-Dole viscosity B-coefficient, temperature derivative of B-coefficient i.e.(dB/dT) and hydration number (nH). Free energy of activation for viscous flow per mole of solvent (Δμ10#), per mole of solute (Δμ20#), entropy of activation per mole of viscous flow of solution (TΔS20#) and enthalpy of activation (ΔH20#) have also been computed through B-coefficient. These significant parameters have been discussed in terms of different molecular interactions.

Polysaccharide type and concentration affect nanocomplex formation in associative mixture with β-lactoglobulin

The main objective of this work was to investigate the effects of polysaccharide type (gum Arabic, GA and/or carboxymethyl cellulose, CMC) and concentration (0–0.2% (w/w)) on the electrostatic interactions with β-lactoglobulin (BLG). Biopolymer interaction was studied using turbidimetric analysis, dynamic light scattering (DLS), electrophoretic mobility and relative viscosity measurements. Complexes were developed at pH values below the isoelectric point (pI) of BLG. Increasing polysaccharide concentration increased the stability of nanocomplexes through increasing the negative charges carried by complexes. The differences between GA and CMC were attributed to the polysaccharide structure (linear or branched chains), charge density and flexibility. Phase contrast optical microscopy showed that complexation was of nucleation and growth type mechanism. Relative viscosity measurements confirmed that wrapping phenomenon occurred in both associative mixtures.

Taylor Dispersion Analysis as a promising tool for assessment of peptide-peptide interactions

Protein-protein and peptide-peptide (self-)interactions are of key importance in understanding the physiochemical behavior of proteins and peptides in solution. However, due to the small size of peptide molecules, characterization of these interactions is more challenging than for proteins. In this work, we show that protein-protein and peptide-peptide interactions can advantageously be investigated by measurement of the diffusion coefficient using Taylor Dispersion Analysis. Through comparison to Dynamic Light Scattering it was shown that Taylor Dispersion Analysis is well suited for the characterization of protein-protein interactions of solutions of α-lactalbumin and human serum albumin. The peptide-peptide interactions of three selected peptides were then investigated in a concentration range spanning from 0.5mg/ml up to 80mg/ml using Taylor Dispersion Analysis. The peptide-peptide interactions determination indicated that multibody interactions significantly affect the PPIs at concentration levels above 25mg/ml for the two charged peptides. Relative viscosity measurements, performed using the capillary based setup applied for Taylor Dispersion Analysis, showed that the viscosity of the peptide solutions increased with concentration. Our results indicate that a viscosity difference between run buffer and sample in Taylor Dispersion Analysis may result in overestimation of the measured diffusion coefficient. Thus, Taylor Dispersion Analysis provides a practical, but as yet primarily qualitative, approach to assessment of the colloidal stability of both peptide and protein formulations.

Rheological Properties and Crosslinking Rheo-Kinetics of CMHEC/CTAB Synergistic Systems

Aiming at synergistic interaction between carboxymethyl hydroxyethyl cellulose (CMHEC) and cetyltrimethyl ammonium bromide (CTAB), mixtures of CMHEC and CTAB solutions were investigated, employing relative viscosity and rheological measurements. The effects of mass ratio of CMHEC and CTAB solutions, temperature, and polysaccharide concentration on relative viscosities of CMHEC/CTAB systems were studied. Rheological method was used to study rheo-kinetics of the isothermal crosslinking process for CMHEC/CTAB synergistic fracturing fluid, and the novel crosslinking rheo-kinetics equation was established. The results showed the strong synergism between CMHEC and CTAB, resulting in a higher relative viscosity, storage modulus G′, and loss modulus G″ than that of separate ones. CMHEC/CTAB systems behave as pseudoplastic fluids with considerable thixotropy and viscoelasticity, and the flow behavior can be well described by Carreau−Williamson model. The crosslinking rheo-kinetics equation can well describe the isothermal crosslinking process at different shear rates. The model parameters are well-defined and reasonable.

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.

Kinetic of the enzymatic degradation of chitosan using bromelain: a viscosimetric study

Enzymatic degradation of chitosan (degree of acetylation (da) and average viscosimetric molecular weight (MV) of 0.85 and 310 kDa, respectively) was carried out using commercial bromelain. Decrease of the average viscosimetric polymerization degree (XV) was studied in a buffer solution of acetic acid (0.3 M)/sodium acetate (0.2 M) at 25 ºC. Under these experimental conditions it is possible to relate the instantaneous intrinsic viscosity [η] with MV through the Mark-Houwink-Sakurada equation. Equations of Sano, Solomon-Ciuta, Deb-Chatterjee and Ram-Yaseen, which allow to compute values of [η] with a single measurement of relative (ηrel) and/or specific viscosity (ηsp), were employed to obtain instantaneous values of [η]. Instantaneous values of [η] were also obtained through an iterative process using Huggins equation. Initial velocity of depolymerization (vo) was obtained from different concentration of chitosan solutions and a fixed bromelain concentration. Michaelis-Menten constant (kM) and maximum velocity (Vm) were obtained using the Lineweaver-Burk representation of the Michaelis-Menten equation for each set of [η] which were calculated employing all procedures mentioned. Best kinetic parameters for chitosan depolymerization (kM=3.92x10-7 mol.dL-1; Vm=9.09x10-8 mol.dL-1.s-1) were obtained when Sano`s equation was employed to calculate [η] values.

Determination of critical micelle concentrations of ionic and nonionic surfactants based on relative viscosity measurements by capillary electrophoresis

The critical micelle concentration (CMC) can be obtained by measuring the distinct physical properties of surfactant molecules in the monomeric and micellar states. In this study, two linear increments of relative viscosity with distinct slopes were obtained when increasing surfactant concentrations from dilute solution to above the CMC, which was then determined by the intersection of the two linear extrapolations. Using a capillary electrophoresis (CE) instrument and Poiseuille’s law, the viscosities of surfactants at a series of concentrations covering the monomeric and micellar regions could be obtained by measuring the hydrodynamic flow rates of the corresponding surfactant solutions. We applied this method to determine the CMC values of various types of surfactants including anionic, cationic, zwitterionic, and nonionic surfactants. The resulting CMC values were all in good agreement with those reported in literature. Using this method, the multiple-stage micellization process of a short-chain surfactant was revealed. We have also demonstrated that the CE-based viscometer was applicable to the study of CMC variation caused by organic or electrolyte additives.

Organic matrix effects on the formation of light-absorbing compounds from α-dicarbonyls in aqueous salt solution

Aqueous-phase reactions of organic compounds are of general importance in environmental systems. Reactions of α-dicarbonyl compounds in the aqueous phase of atmospheric aerosols can impact their climate-relevant physical properties including hygroscopicity and absorption of light. Less-reactive water-soluble organic compounds may contribute an organic matrix component to the aqueous environment, potentially impacting the reaction kinetics. In this work we demonstrate the effects of organic matrices on the self-reactions of glyoxal (Gly) and methylglyoxal (mGly) in aqueous solutions containing ammonium sulfate. At an organic-to-sulfate mass ratio of 2 : 1, carbohydrate-like matrices resembling oxidized organic aerosol material reduce the rate of formation of light-absorbing products by up to an order of magnitude. The greatest decreases in the reaction rates were observed for organic matrices with smaller, more linear molecular structures. Initial UV-Vis spectra, product studies, relative rate data, acidity changes, and viscosity measurements suggest that shifts in carbonyl equilibria, due in part to (hemi)acetal formation with the matrix, reduce the rate of formation of light-absorbing imidazole and oligomer species.

Thermo-mechanical behaviour of Polyamide 6 chain extended with 1,1′-Carbonyl-Bis-Caprolactam and 1,3-Phenylene-Bis-2-Oxazoline

A commercial Polyamide 6 (PA6) was melt compounded by using a twin screw extruder with a combination of 1,1′-Carbonyl-Bis-Caprolactam (CBC) and 1,3-Phenylene-Bis-2-Oxazoline (PBO), in order to evaluate their effect on the chain extension behaviour of the resulting materials. An increase of the viscosity values with the chain-extender amount was evidenced by rheological tests on the compounded pellets and relative viscosity measurements on solubilized samples, while the opposite trend was determined increasing the residence time at elevated temperatures. The increase of the molecular weight due to the presence of CBC and PBO was confirmed by the reduction of carboxylic and aminic functionalities evidenced in end group analysis. DSC tests showed a reduction of the melting temperature and of the crystallinity degree proportionally to the chain extender amount. Elastic modulus of the chain-extended materials was similar to that of the corresponding PA6 grades at different molecular weight, while crystallinity drop due to chain extension determined an increase of the strain at break values.

Chain extension behavior and thermo-mechanical properties of polyamide 6 chemically modified with 1,1′-carbonyl-bis-caprolactam

A chain-extender based on 1,1′-Carbonyl-Bis-Caprolactam (CBC) was melt compounded with a commercial Polyamide 6 (PA6) by using a twin screw extruder. Rheological, thermal, and mechanical tests were performed on the resulting materials to evaluate the chain extension capability of CBC. Rheological tests on the compounded pellets and relative viscosity measurements on solubilized samples evidenced an increase of the viscosity values with the chain-extender amount, while the opposite trend was determined increasing the high temperature residence time. Terminal group analysis confirmed the increase of the molecular weight with the CBC content and highlighted a preferential reactivity of the chain-extender with aminic end groups. Differential scanning calorimetry (DSC) tests showed how both melting and relative crystallinity of the up-graded samples decreased with the CBC amount. Elastic and yield properties of chain-extended PA6 were similar to those of neat PA6 grades at different molecular weight, while crystallinity drop due to chain extension was responsible of an increase of the strain at break values. POLYM. ENG. SCI., 54:158–165, 2014. © 2013 Society of Plastics Engineers

Thermo-mechanical properties of Polyamide 6 chemically modified by chain extension with Polyamide/Polycarbonate blend

A Polycarbonate/Polyamide (PCPA) blend was used as chain extender in a melt compounding process with a Polyamide 6 (PA6), by using a twin screw extruder. The chain extension capability of the PCPA blend was evaluated through rheological, thermal and mechanical tests. Rheological tests on the compounded pellets and relative viscosity measurements on solubilized samples evidenced an increase of the viscosity values with the chain-extender amount and with the high temperature residence time. Terminal group analysis confirmed the increase of the molecular weight with the PCPA content and highlighted a preferential reactivity of the chain extender with amminic end groups. DSC tests showed a slight crystallinity decrease with the PCPA content, while both melting and crystallization temperatures were unaffected. Elastic and yield properties of chain-extended PA6 were similar to that of neat PA6 at different molecular weights, while crystallinity drop due to chain extension produced an increase of the strain at break values.

Electrokinetic and rheological properties of kaolinite in poly(diallyldimethylammonium chloride), poly(sodium 4-styrene sulfonate) and poly(vinyl alcohol) solutions

The zeta potential and viscosity values of kaolinite suspensions in cationic poly(diallyldimethylammonium chloride) (PDDACl), anionic poly(sodium 4-styrene sulfonate) (PSSS) and nonionic poly(vinyl alcohol) (PVA) solutions have been determined. The zeta potential value of kaolinite increases with the first addition of PDDACl and PVA solutions, on the contrary of PSSS. Kaolinite–water suspensions exhibit a thixotropic or rheopectic behavior depending on clay concentration. However, kaolinite–polymer suspensions display a thixotropic behavior. The flow type of kaolinite–water and kaolinite–polymer suspensions is Bingham, except kaolinite–PVA suspensions including 7.5 × 10 −5 and 1.0 × 10 −4 M PVA. It has been found from the relative plastic viscosity measurements that PDDACl and PVA are of a significant effect on the plastic viscosity values of kaolinite suspensions, unlike the PSSS. The interactions between kaolinite and polymer molecules have been investigated by FTIR spectroscopy. This study shows that the zeta potential and viscosity values of kaolinite suspensions can be adjusted using different polymers.

Synthesis and applications of main-chain Ru(ii) metallo-polymers containing bis-terpyridyl ligands with various benzodiazole cores for solar cells

A series of π-conjugated bis-terpyridyl ligands (M1–M3) bearing various benzodiazole cores and their corresponding main-chain Ru(II) metallo-polymers were designed and synthesized. The formation of metallo-polymers were confirmed by NMR, relative viscosity, and UV-visible titration measurements. The effects of electron donor and acceptor interactions on their thermal, optical, electrochemical, and photovoltaic properties were investigated. Due to the strong intramolecular charge transfer (ICT) interaction and metal to ligand charge transfer (MLCT) in Ru(II)-containing polymers, the absorption spectra covered a broad range of 260–750 nm with the optical band gaps of 1.77–1.63 eV. In addition, due to the broad sensitization areas of the metallo-polymers, their bulk heterojunction (BHJ) solar cell devices containing [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor exhibited a high short-circuit current (Jsc). An optimum PVC device based on the blended polymer P1:PCBM = 1:1 (w/w) achieved the maximum power conversion efficiency (PCE) value up to 0.45%, with Voc = 0.61 V, Jsc = 2.18 mA cm−2, and FF = 34.1% (under AM 1.5 G 100 mW cm−2), which demonstrated a novel family of conjugated polyelectrolytes with the highest PCE value comparable with BHJ solar cells fabricated from ionic polythiophene and C60.

A class of novel carboline intercalators: Their synthesis, in vitro anti-proliferation, in vivo anti-tumor action, and 3D QSAR analysis

Based on DOCK scores 18 N-(3-benzyloxycarbonylcarboline-1-yl)ethylamino acid benzylesters ( 6a– r) were synthesized as anti-tumor agents. Their IC 50 values against five human carcinoma cell lines ranged from 11.1 μM to more than 100 μM. The in vivo assay identified five derivatives of them had no anti-tumor action, the anti-tumor activity of nine derivatives of them equaled that of cytarabine, and the anti-tumor activity of three derivatives of them was higher than that of cytarabine. The UV and fluorescence spectra, as well as the relative viscosity and melting temperature measurements of calf thymus DNA (CT DNA) with and without the representative compound suggested that DNA intercalation could be their action mechanism. The 3D QSAR analysis of N-(3-benzyloxycarbonylcarboline-1-yl)ethylamino acid benzylesters ( 6a– r) revealed that their in vivo anti-tumor activity significantly depends on the molecular electrostatic and steric fields of the side chain of the amino acid residue.

Counterion Effect of Cationic Surfactants Upon the Interaction with Poly(methacrylic acid)

AbstractThis work investigates decylammonium salts, with inorganic (chloride and thiocyanate) and organic (acetate and butyrate) counterions, in interaction with poly(methacrylic acid) (PMA). The study is conducted by means of surface tension, relative viscosity and pH measurements. The role of the methyl group in PMA appears by comparison with analogous mixtures of poly(acrylic acid) (PAA). In aqueous solution, a non‐cooperative interacti between the surfactant and the hydrophobic microdomains (HMD) of PMA starts first. With surfactant addition, micellar aggregates bound onto the polymer chain appear at a concentration T1, which is higher than for the analogous PAA systems, but lower than the respective CMC. T1 is lower for chloride than for thiocyanate and lower for acetate than for butyrate. Depending on the counterion, the HMD conceal or expose carboxyl groups, with influence upon the interaction strength and the bulk and surface behavior. Stronger interactions and maxima of surface tension and relative viscosity appear for the systems with organic counterions. An estimation of the interaction strength shows weaker surfactant interactions with PMA than with PAA, and that acetate induces the strongest interaction while thiocyanate the weakest.

Sonolytic, sonocatalytic and sonophotocatalytic degradation of chitosan in the presence of TiO 2 nanoparticles

The degradation of chitosan by means of ultrasound irradiation and its combination with heterogeneous (TiO 2) was investigated. Emphasis was given on the effect of additives on degradation rate constants. Ultrasound irradiation (24 kHz) was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. The extent of sonolytic degradation increased with increasing ultrasound power (in the range 30–90 W), while the presence of TiO 2 in the dark generally had little effect on degradation. On the other hand, TiO 2 sono-photocatalysis led to complete chitosan degradation in 60 min with increasing catalyst loading. TiO 2 sonophotocatalysis was always faster than the respective individual processes due to the enhanced formation of reactive radicals as well as the possible ultrasound-induced increase of the active surface area of the catalyst. The degraded chitosans were characterized by X-ray diffraction (XRD), gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated chitosan was determined by measurements of relative viscosity of samples. The results show that the total degree of deacetylation (DD) of chitosan did not change after degradation and the decrease of molecular weight led to transformation of crystal structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within the degradation process was suggested.

Compatibility and biodegradability studies of linseed oil epoxy and PVC blends

Abstract With the aim to utilize linseed oil epoxy – a product from sustainable resource for the processing of hard polymers, blends of linseed oil epoxy (LOE) with polyvinylchloride (PVC) were prepared for the first time by solution blending of the requisite amounts of the two components in the weight ratios LOE/PVC- 85/15, 65/35, 55/45, 45/55, 35/65, and 15/85 through solution method by mixing in tetrahydrofuran (THF). The miscibility of the two components in solution phase was investigated by relative viscosity, reduced viscosity and density measurements. The blend with 85 wt% of LOE yielded stiff and flexible films with maximum stress of 33 MPa and 216% elongation at break. Biodegradability of these blends has been studied by soil burial test, enzymatic degradation, and hydrolytic degradation in phosphate buffer. The blend LOE/PVC 85/15 showed the highest biodegradation of 68 wt% in 6 months in the soil burial test. The degradability was found to increase with the increase in LOE content in the blend compositions. The potential applications for such sustainable resource based blend films include packaging materials and biodegradable plastic sheets which can be formed into products such as bio-bags.

Live Cell Cytotoxicity Studies: Documentation of the Interactions of Antitumor Active Dirhodium Compounds with Nuclear DNA

The promising antitumor activity of dirhodium complexes has been known for over 30 years. There remains, however, a general lack of understanding of their activity in cellulo. In this study, we report the DNA interactions and activity in living cells of six monosubstituted dirhodium(II,II) complexes of general formula [Rh(2)(mu-O(2)CCH(3))(2)(eta(1)-O(2)CCH(3))(L)(CH(3)OH)](+), where L = bpy (2,2'-bipyridine) (1), phen (1,10-phenanthroline) (2), dpq (dipyrido[3,2-f:2',3'-h]quinoxaline) (3), dppz (dipyrido[3,2-a:2',3'-c]phenazine) (4), dppn (benzo[i]dipyrido[3,2-a:2',3'-c]phenazine) (5), and dap (4,7-dihydrodibenzo[de,gh][1,10]phenanthroline) (6). DNA interactions were investigated by UV/visible spectroscopy, relative viscosity measurements, and electrophoretic mobility shift assay. These measurements indicate that compound 5 exhibits the strongest interaction with DNA. Compound 5 also causes the most damage to DNA after cellular internalization, as evaluated by the alkaline comet assay. Compound 5, however, is not the most effective at inhibiting cell viability of the human cancer cells HeLa and COLO-316. The greater hydrophobicity of 5 as compared to that of 4, which is the most effective compound in the series, hinders its ability to reach its cellular target(s). Data from modulation studies of glutathione using N-acetylcysteine and L-buthionine-sulfoximine indicate that changes in glutathione levels do not affect the activity of these particular dirhodium complexes. These results suggest that glutathione is not the only agent involved in the deactivation of these dirhodium complexes.

Study on the interfacial properties of viscous capillary flow of dilute acetic acid solutions of chitosan

The relative viscosities of acetic acid solutions of chitosan at varied temperatures were measured in a common glass capillary Ubbelohde viscometer in the range from dilute down to extremely dilute concentration. With the aid of the newly proposed theory related to the effect of solute adsorption on the relative viscosity measurement, the experimental data was analyzed, and some interesting parameters describing the interfacial properties of viscous capillary flow were deduced. The change of the conformation of the chitosan chains both free dissolved in solution and adsorbed on the glass capillary surface were discussed in detail. Furthermore, the morphologies of the adsorbed chitosan was also observed by AFM.

Spectroscopic and thermal studies on acrylic acid copolymers in interaction with uranyl

Two acid copolymers derived from acrylic acid and itaconic acid i.e., poly(AA-co-IA) (7:2 molar ratio) or from the same acids and a small amount of N-vinylpyrrolidone i.e., poly(AA-co-IA-co--NVP) (7:3:2 molar ratio) were prepared by standard free-radical polymerization in aqueous solutions to be further used in preparation of complexes with uranyl ions. FT-IR and 1 H NMR spectroscopy, thermogravimetric and relative viscosity measurements were used to characterize the resulting copolymers (PA-B, PA-T). Their polycomplexes with uranyl acetate, in aqueous solution and solid state (PA-Baq, PA-Taq and PA-Bss, PA-Tss, respectively), were analyzed by pH measurements, luminescence spectroscopy, FT-IR spectroscopy and thermal analyses for the latter ones.