Capillary Viscometry Research Articles

Hydrodynamic properties of some cationic amphiphilic polysaccharides in dilute and semi-dilute aqueous solutions

The dynamic properties of aqueous solutions of amphiphilic cationic polyelectrolytes based on polysaccharides with N,N-dimetyl-N-alkyl-N-(2-hydroxypropyl)ammonium chloride pendant groups were studied by capillary viscometry over a large concentration range (0.01–10 g/dL), as a function of the degree of substitution with pendant groups, length of the alkyl substituent (C 8, C 12, C 16), molar mass and nature of polysaccharide backbone. Intrinsic viscosity determined in dilute solution using Rao or Heller equations provided information on the conformation of individual polymer chains. Comparison of the specific viscosity–concentration relationships with scaling theories allowed the delimitation of concentration domains and calculation of overlap and entanglement concentrations. Semi-empirical equations (Fedors, Martin) could describe the viscosity variation with concentration only for polymers with low degree of substitution (<10 mol%). All these studies help to identify the predominant characteristic for each amphiphilic polyelectrolyte (neutral, charged or associative polymer), determined by its chemical structure, as a result of the balance between electrostatic repulsion and intra- or/and intermolecular associations. The obtained information could be very useful to tailor the cationic amphiphilic polysaccharide's chemical structure to the viscometric properties suitable to different application as flocculants, thickeners or drug delivery systems.

Influence of the Solvent Quality on the Thermodynamic Behavior of Polymethylphenylsiloxane Solutions

In this work we investigate the effect of the solvent quality on the thermodynamic behavior of the polydimethyldiphenylsiloxane copolymer by using turbidimetry and viscosimetry. The turbidimetric method was used for the determination of the composition of the solvent mixture at the theta point. The experimental data obtained by using the capillary viscometry both in good and theta solvent conditions have been processed by using classical Huggins equation and new Wolf model (2007), which allows the calculation of intrinsic viscosities and other hydrodynamic parameters. The results obtained by using the two approaches were discussed comparatively. The conformational properties of copolymer in solution depend on their molecular structure, which is essentially dominated by the solvent quality, reflecting the balance of the interactions between the polymer chains and each solvent and that between solvent molecules.

Synthesis and physicochemical evaluation of a new carrier based on an interpolyelectrolyte complex formed by Eudragit® EPO and Carbomer 940

The formation of interpolyelectrolyte complexes (IPEC) between Eudragit® EPO (EPO) and Carbomer 940 (C940) was investigated with a view to their use in peroral controlled-release drug delivery systems. The structure of the synthesized products was investigated using FTIR spectroscopy and MT—DSC methods, which indicated that the synthesized product can be considered to be an IPEC stabilized by a cooperative system of ionic bonds. Based on results of capillary viscosimetry and elemental analysis, the IPEC prepared at pH 4.0 has a characteristic composition with a C940:EPO mole ratio of 1.75:1.

Ultrasonic degradation for molecular weight reduction of pharmaceutical cellulose ethers

Several pharmaceutical grade cellulose ethers, hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC), hydroxyethyl cellulose (HEC) and ethylhydroxyethyl cellulose (EHEC) have been degraded to different molecular weights by exposing either a 1.5 or 4.0 wt.% aqueous solution of the polymer to varying periods of ultrasonic radiation over 24 h. The resulting solutions were characterised with respect to molecular weight and molecular weight distribution of the polymer using capillary viscometry, size exclusion (SEC) and in the case of HPC, dynamic and static light scattering. Depending upon the ultrasonication time, a range of polymer solutions were produced over a range of molecular weights in a suitable form for further experimental use. In all cases a limiting polymer molecular weight was reached after 24 h of ultrasonic degradation; the limiting polymer molecular weight was dependent upon the nature of the polymer and not the concentration of the polymer solution. From measurements of intrinsic viscosity using capillary viscometry and molecular weight using static light scattering, the Mark-Houwink parameters of HPC were found to be K = 6.25 × 10 −5 and a = 0.84 over the molecular weight range 139,000–58,000 relative molecular mass.

Molecular characteristics of a novel water-soluble polysaccharide from the New Zealand black tree fern ( Cyathea medullaris)

A water-soluble polysaccharide fraction isolated from the fronds of the black tree fern ( Cyathea medullaris or ‘Mamaku’ in Māori) was characterised using capillary viscometry, multi-angle laser light scattering and dynamic light scattering techniques. The intrinsic viscosity [ η ] of the native polymer was ∼2020 ± 23 mL/g (in Milli-Q water). The weight-average molar mass M w and the root-mean square ( R g 2 ) z 1 / 2 radius of the polymer molecules in 0.1 M NaCl, determined using a size-exclusion chromatography coupled to a multi-angle laser light scattering (SEC-MALLS), were ∼3 × 10 6 Da and ∼144 nm respectively. The z-average diameter of the samples obtained by dynamic light scattering was ∼75 nm. Based on the Smidsrød-Haug’s stiffness parameter B (∼0.015); the exponent of ( R g 2 ) z 1 / 2 versus M w (∼0.60); and the shape-factor ( p) of ( R g 2 ) z 1 / 2 / R h (∼1.8), the results suggest that the polymer molecule adopted a semi-flexible (extended) random coil conformation in 0.1 M NaCl solution.

Synthesis and properties of siloxane(ethylene oxide)urethane block copolymers

A new approach to the synthesis of hydrolytically stable dimethylsiloxane-ethylene oxide polyblock copolymers is described, in which ethylene oxide and siloxane blocks are linked by urethane groups. The molecular-mass parameters of block copolymers of different compositions are determined by capillary viscometry, light scattering, and gel-permeation chromatography. The temperature transitions in copolymers are characterized by differential scanning calorimetry.

Structural and rheological properties of chitosan semi-interpenetrated networks

The local structure and the viscoelastic properties of semi-interpenetrated biopolymer networks based on cross-linked chitosan and poly(ethylene oxide) (PEO) were investigated by Small Angle Neutron Scattering and rheological measurements. The specific viscosity and the entanglement concentration of chitosan were first determined, respectively, by capillary viscosimetry and steady-state shear rheology experiments performed at different polymer concentrations. Mechanical spectroscopy was then used to study the gelation process of chitosan/PEO semi-interpenetrated networks. By fitting the frequency dependence of the elastic and loss moduli with extended relations of relaxation shear modulus around the sol-gel transition, it was shown that the addition of PEO chains had a significant effect on the viscoelastic properties of aqueous chitosan networks but no effect on the gelation time. The improvement of mechanical properties was in accordance with the correlation length decrease deduced from Small Angle Neutron Scattering experiments.

Cationic acrylamide copolymers and terpolymers as flocculants for model aqueous suspensions

Summary — Cationic acrylamide copolymers with diallyldimethylammonium chloride and terpolymers of the both monomers with N-vinylformamide were synthesized, characterized by capillary viscometry and their flocculation efficiency evaluated by extinction, sludge volume and solid matter recovery measurements. The polymerization reactions were carried out either as thin-layer processes in aqueous solutions or as microsuspension polymerization. The results from the numerous flocculation tests performed on model aqueous suspensions of fine coal, colloidal silica and talc have been presented and discussed. Flocculation efficiency was determined taking into account the type and dose of the used copolymer.

Solution properties of hyaluronic acid and comparison of SEC‐MALS‐VIS data with off‐line capillary viscometry

AbstractExtensive study of solution properties of sodium hyaluronate including about 140 samples and covering broad molar mass range was carried out by classical viscometry using an Ubbelohde capillary viscometer and by combination of size‐exclusion chromatography with a multi‐angle light scattering detector and an on‐line viscometer. The study also involved critical overview of literature data of Mark‐Houwink relation for sodium hyaluronate. Continuous decrease of the Mark‐Houwink exponent with increasing molar mass to the values markedly lower than those typical of linear random coils in thermodynamically good solvents was observed. This fact was attributed to branched molecular structure of hyaluronic acid as a result of unknown side reactions during the manufacturing process. The molar mass dependence of the second virial coefficient was determined and proved aqueous salt solutions to be thermodynamically good solvents for sodium hyaluronate. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Final report on CCM.V-K2.1 comparison

This report describes a CCM key comparison in capillary viscometry at six national metrology institutes, which was carried out between October 2008 and January 2009. This comparison is a follow-up of key comparison CCM.V-K2 carried out in 2006–2007. It was carried out at the request of laboratories that were not able to participate in key comparison CCM.V-K2 or reported unsatisfactory results.The objective was to compare viscosity measurements made at 20 ºC, 60 ºC and 100 ºC using a standard fluid with nominal viscosities at these temperatures of 1300 mm2 s−1, 150 mm2 s−1 and 40 mm2 s−1, respectively.For 20 °C and 100 ºC, the results from two participants, PTB and Cannon, were used to link the measurement results of this key comparison to those of key comparison CCM.V-K2 and thus calculate the degrees of equivalence with respect to the key comparison reference value of CCM.V-K2. Since in key comparison CCM.V-K2 no measurements were carried out at 60 ºC, at this temperature no linkage could be provided. Also no reference value could be computed at 60 ºC, because there are only three participants with independent measurement scales, one of which has withdrawn a clearly outlying result at this temperature.For 20 °C and 100 ºC, none of the reported results show a significant difference from the key comparison reference value of CCM.V-K2.Main text.To reach the main text of this paper, click on Final Report.Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Rheology Study of Chlorinated Polyethylene with Various Cl-Contents and Carbon Nanotube Composites

Composites of chlorinated polyethylene with various Cl-contents and carbon nanotubes (CNT) were produced and their rheological behaviors were characterized by capillary viscometry. For polyethylene (PE)/CNT composites with CNT loadings of 3 wt% and 5 wt%, the melt viscosity was higher than that of PE alone. However, the PE/CNT composite with CNT loading of 2 wt% gave a much lower melt viscosity than that of PE alone. The melt viscosity of chlorinated polyethylene (PECl)/CNT composites prepared also depended on the amount of added CNT and chlorine content. PECl/CNT composites with higher chlorine content displayed lower melt viscosities than that of PECl alone. A mechanism was proposed.

Surface tension effects in capillary viscometers: an evaluation with an experimental comparative analysis

Surface tension effects in capillary viscometry play an important role in the accuracy of the measurements of kinematic viscosity. An experimental evaluation of these effects has been carried out using capillary viscometers having the same shape and size of the upper and lower bulbs, the same timing bulb, the same capillary radius, but different capillary lengths. The measurement method applied for evaluating the correction factor and its associated uncertainty is described. As an example, results of the kinematic viscosity of the liquid n-nonane, obtained with two Ubbelohde viscometers, which have been calibrated with bi-distilled water, are presented.

Ionic Polymers Based on Dextran: Hydrodynamic Properties in Aqueous Solution and Solvent Mixtures

Hydrodynamic properties of a series of ionic polysaccharides with different charge density but the same molecular weight have been evaluated in salt-free aqueous solution and aqueous/organic solvent mixtures by means of capillary viscometry. The polyelectrolytes investigated contain quaternary ammonium salt groups, N-ethyl-N,N-dimethyl-2-hydroxypropylammonium chloride, attached to a dextran backbone. The experimental viscometric data have been plotted in terms of the Wolf method. The results show that the experimental data fit well with this model and allow the calculation of intrinsic viscosities and other hydrodynamic parameters, which provide new information about the dependence of the polyion conformation on its polyion charge density as well as on solvent composition.

Micellization in solutions of hybrid block copolymer of poly(methyl methacrylate) and hyperbranched perfluorinated poly(phenylene germane)

Fractions of the product resulting from the polymerization of methyl methacrylate in the presence of hyperbranched perfluorinated poly(phenylene germane) have been studied by dynamic and static light scattering and capillary viscometry in methyl ethyl ketone solutions. The hybrid product is obtained via the reaction of the chain transfer of methyl methacrylate propagating radicals to pentafluorophenyl groups. Eight fractions have been isolated by fractional precipitation, including fractions of the linear-dendrite block copolymer. Light scattering studies have shown that hybrid macromolecules containing 15–20 wt % hyper-branched fragments form micelles in solutions.

Solution behavior and surface properties of carboxymethylcellulose acetate butyrate

Solution behavior of carboxymethylcellulose acetate butyrate (CMCAB) in acetone and ethyl acetate has been investigated by small-angle X-ray scattering (SAXS) and capillary viscometry and correlated with the characteristics of CMCAB films. Viscosity and SAXS measurements showed that ethyl acetate is a better solvent than acetone for CMCAB. Thin films of CMCAB were deposited onto silicon wafers (Si/SiO2) by spin coating. AFM images revealed that CMCAB spin coated films from solutions prepared in ethyl acetate were homogeneous and flat. However, films obtained from solutions in acetone were very rough. Contact angle measurements with polar and apolar test liquids characterized CMCAB surfaces as hydrophobic and allowed estimating the surface energy of CMCAB. Sum frequency generation vibrational spectroscopy was used to understand the role played by solvents and to gain insight about molecular orientation at Si/SiO2/CMCAB interface.

Organic-inorganic hybrid hydrogels based on linear poly(N-vinylpyrrolidone) and products of hydrolytic polycondensation of tetramethoxysilane

The initial stage of gelation of organic-inorganic hybrid hydrogels based on poly(N-vinylpyrrolidone) and the products of hydrolytic polycondensation of tetramethoxysilane has been studied by capillary viscometry. The development of strong bonds between polymer molecules and silica particles in aqueous solutions is proved by the electrokinetic sonic amplitude method. The molecular mass of poly(N-vinylpyrrolidone), the concentration of starting components, and their total amount affect the onset time of gelation in poly(N-vinylpyrrolidone)—water—tetramethoxysilane systems. The general scheme of formation of three-dimensional networks in such systems under the conditions of mutual penetration of poly(N-vinylpyrrolidone) coils is suggested. According to this scheme, nanoparticles of the general formula SiOx(OH)y(OR)z linking poly(N-vinylpyrrolidone) macromolecules serve as junctions of the gel network due to the formation of hydrogen bonds between hydrogens of silanol groups of organosilanes and oxygens of carbonyl groups of poly(N-vinylpyrrolidone).

Cold-set thickening mechanism of β-lactoglobulin at low pH: Concentration effects

There is an interest in developing protein based thickening agents for nutritional considerations. A procedure to convert whey protein concentrates or isolates into a pH modified cold-thickening ingredient was developed. Concentration effects on thickening mechanism of this whey protein ingredient were studied with a β-lactoglobulin model system at the pH of the modification procedure, 3.35. In this study, concentration effects on thermal aggregation of β-lactoglobulin were studied at low pH using capillary and rotational viscometry, transmission electron microscopy (TEM), and high performance liquid chromatography coupled with multi-angle laser light scattering (HPLC-MALS). From the results of capillary viscometry, a critical concentration ( C c ∼ 6.9% w/w) was identified below which no significant thickening functionality could be achieved. Microscopy revealed formation of flexible fibrillar network at pH 3.35 during heating at all concentrations. These flexible fibrils had a diameter of about 5 nm and persistence length of about 35 nm as compared to more linear and stiff fibrils formed at pH 2 and low ionic strength conditions. Under similar heating conditions at concentration above C c, larger aggregates similar to microgels were observed compared to the concentration below C c, where isolated fibrils with an average contour length of about 130 nm were observed. These microgels and apparently stronger interactions between aggregates at concentrations above C c were seemingly responsible for thickening functionality of heated β-lactoglobulin solutions and subsequently modified powders. Further investigation of β-lactoglobulin aggregation at this pH may provide capability to mechanistically tailor the functional attributes of modified ingredients.

Physicochemical features of ultra-high viscosity alginates

The physicochemical characteristics of the ultra-high viscosity and highly biocompatible alginates extracted from Lessonia nigrescens (UHV N) and Lessonia trabeculata (UHV T) were analyzed. Fluorescence and 1H NMR spectroscopies, viscometry, and multi-angle light scattering (MALS) were used for elucidation of the chemical structure, molar mass, and coil size. The sequential structures from NMR spectroscopy showed high guluronate content for UHV T, but low for UHV N. Intrinsic viscosity [ η] measurements exhibited unusual high values (up to 2750 mL/g), whereas [ η] of a commercial alginate was only about 970 mL/g. MALS batch measurements of the UHV-alginates yielded ultra-high values of the weight average molar mass ( M w up to 1.1 × 10 6 g/mol) and of the z-average gyration radius (〈 R G〉 z up to191 nm). The M w and 〈 R G〉 z distributions of UHV-alginates and of ultrasonically degraded fractions were determined using size exclusion chromatography combined with MALS and asymmetrical flow-field-flow fractionation. The M w dependency of [ η] and 〈 R G〉 z could be described by [ η] = 0.059 × M w 0.78 and 〈 R G〉 z = 0.103 × M w x . (UHV N: x = 0.52; UHV T: x = 0.53) indicating that the monomer composition has no effect on coil expansion. Therefore, the equations can be used to calculate M w and 〈 R G〉 z values of UHV T- and UHV N-alginate mixtures as used in immunoisolation. Furthermore, the simple and inexpensive capillary viscometry can be used for real-time validation of the extraction and purification process of the UHV-alginates.

Use of Viscosity to Probe the Interaction of Anionic Surfactants with a Coagulant Protein from Moringa oleifera Seeds

The intrinsic viscosity of the coagulant protein was evaluated from the flow times of the protein solutions through a capillary viscometer, and the results suggested the coagulant protein to be globular. The interactions of the coagulant protein with anionic surfactant sodium dodecyl sulphate (SDS) and sodium dodecyl benzene sulfonate (SDBS) were also investigated by capillary viscometry. We conclude that there is strong protein‐surfactant interaction at very low surfactant concentrations, and the behavior of the anionic surfactants in solutions containing coagulant protein is very similar. The viscometry results of protein‐SDS system are compared with surface tension, fluorescence, and circular dichroism reported earlier. Combining the results of the four studies, the four approaches seem to confirm the same picture of the coagulant protein‐SDS interaction. All the physical quantities when studied as function of surfactant concentration for 0.05% (w/v) protein solution either exhibited a maximum or minimum at a critical SDS concentration.

Final report on CCM.V-K2 comparison

This report describes the second CCM key comparison in capillary viscometry at nine national metrology institutes (NMIs), which was carried out between April and August 2006. Five NMIs, which do not maintain an independent viscosity scale, also took part in this comparison. One participant submitted changes to their originally submitted results for one liquid and requested that results be withdrawn for a second liquid.Six samples of Newtonian liquids with nominal kinematic viscosities of 80 mm2/s at −40 °C, 20 mm2/s at −20 °C, 5 mm2/s at 20 °C, 1300 mm2/s at 20 °C, 40 mm2/s at 100 °C and 15 mm2/s at 150 °C were used to determine the degrees of equivalence between the individual NMIs and the proposed key comparison reference values (KCRV). From the total number of 54 measurements carried out by all the participating NMIs, 7 measurements (13%) showed deviations from the proposed KCRVs greater than were covered by the measurement uncertainties. This compares to 18 deviations (24%) out of 74 total measurements made in the first key comparison.Linkage to the first key comparison is found at two points—approximately 1300 mm2/s at 20 °C and 40 mm2/s at 100 °C. For this key comparison, 13% of the measurements (3 out of 23) on these two points exceeded the proposed KCRVs by more than were covered by the respective measurement uncertainties.For reference, the first CCM viscosity key comparison (CCM.V-K1) was conducted in 2002.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).