Determination Of Intrinsic Viscosity Research Articles

Comprehensive physical visualisation of the chain conformation and solution property of carboxymethylated konjac glucomannan: Comparison of charged and uncharged polyelectrolytes

The present work deals with a comprehensive molecular characterization and delineation of solution property of a series of charged and uncharged carboxymethylated konjac glucomannan (CMKGM) with different molecular weights (Mw, 1.57 × 105–7.33 × 105) and degrees of substitution (DS, 0.19–1.63) by using various rheological models and solution scaling theory. CMKGM macromolecules in aqueous solutions are found to adopt semi-flexible chain conformation and show a tendency close to rigid chains with decreasing Mw and increasing DS. For uncharged CMKGM solutions, the Huggins–Kraemer, Heller, Fuoss and Wolf approaches can achieve equally excellent fitting results for the determination of intrinsic viscosity [η], whereas for charged CMKGM solutions, only the Huggins–Kraemer and Wolf plots are valid. In accordance with the physical scaling law, a scaling relationship exists between rheological parameters and concentration c for salt and salt-free aqueous solutions of CMKGM. The relationship of specific viscosity ηsp ~ c[η] and ηsp ~ c ~ Mw is derived for CMKGM in a high ionic strength environment (NaCl 0.15 M) by using the Kulicke-Keniewske approach. The constitutive models of the linear Maxwell model and two kinds of non-linear PTT and Giesekus models have also been applied to quantitatively describe the rheological properties of CMKGM entangled solutions under either dynamic or steady shear flow.

Protein intrinsic viscosity determination with the Viscosizer TD instrument: reaching beyond the initially expected applications.

Intrinsic viscosity is a key hydrodynamic parameter to understand molecular structure and hydration, as well as intramolecular interactions. Commercially available instruments measure intrinsic viscosity by recording the macromolecular mobility in a capillary. These instruments monitor Taylor dispersion using an absorbance or fluorescence detector. By design, these instruments behave like U-tube viscometers. To our knowledge, there are no studies to date showing that the Viscosizer TD instrument (Malvern-Panalytical) is able to measure the intrinsic viscosity of macromolecules. In this study, we then performed our assays on the Poly(ethylene oxide) polymer (PEO), used classically as a standard for viscometry measurements and on three model proteins: thebovine serum albumin (BSA), the bevacizumab monoclonal antibody, and the RTX Repeat Domain (RD) of the adenylate cyclase toxin of Bordetella pertussis (CyaA). The presence of P20 in the samples is critical to get reliable results. The data obtained with our in-house protocol show a strong correlation with intrinsic viscosity values obtained using conventional techniques. However, with respect to them, our measurements could be performed at relatively low concentrations, between 2 and 5mg/ml, using only 7µL per injection. Altogether, our results show that the Viscosizer TD instrument is able to measure intrinsic viscosities in a straightforward manner. This simple and innovative approach should give a new boost to intrinsic viscosity measurements and should reignite the interest of biophysicists, immunologists, structural biologists and other researchers for this key physicochemical parameter.

Rapid characterization of high-impact ethylene–propylene copolymer composition by crystallization extraction separation: comparability to standard separation methods

High-impact copolymers of propylene and ethylene are complex materials with several components and at least two different phases, a crystalline polypropylene (PP) matrix and a predominantly amorphous ethylene–propylene copolymer (EPC) normally present as disperse particles. Next to overall composition analysis and morphology studies, fractionation into crystalline and amorphous components followed by further analysis of those components is the most important characterization technique for this technically very relevant class of copolymers. This process, involving separation into xylene cold-soluble (XCS) and insoluble fractions and follow-up determination of intrinsic viscosities (IV) as well as ethylene (C2) content is, however, tedious and time-consuming. A far more rapid approach is presented here through the separation of the amorphous and crystalline fractions of PP in 1,2,4-trichlorobenzene (TCB) using the crystallization extraction technique and the Crystex QC instrument. As the standard methods and Crystex technique are using different solvents (xylene and decalin versus TCB), correlations need to be established in order to be able to compare the results. Based on nine structurally very different polymers, respective correlation curves were developed and predictions for 95% confidence intervals were calculated statistically. In addition, these correlation curves were validated by testing over 100 different PP samples covering a broad range of all tested characteristics. The results show agreement and comparability between the traditional test methods techniques and the Crystex technique inside statistically calculated prediction intervals at 95% over a broad range of all tested characteristics (XCS, C2 and IV).

Determination of intrinsic viscosity of native cellulose solutions in ionic liquids

The weight-average molecular weights of six native cellulose samples in ionic liquids were determined through steady shear viscosity measurements in the ionic liquid butyl methyl imidazolium chloride. The intrinsic viscosity [η] in ethyl methyl imidazolium acetate (EMImAc) is measured using a gravity-driven glass capillary viscometer and found to be independent of temperature in the range of 30–80 °C, disproving a literature report of [η] in EMImAc, exhibiting a strong temperature dependence. Findings are contrasted with values of intrinsic viscosity in cupriethylenediamine hydroxide, the most widely used solvent to dissolve and analyze the molecular weight of cellulose pulps in industry. Differences are tentatively attributed to the different temporary association properties of cellulose chains in the two solvents. Finally, it is demonstrated that cellulose adsorbs at the air/solution interface in three different ionic liquids to create a viscoelastic liquid interfacial layer of higher concentration. Adsorption at the air/solution interface gives an extra contribution to the measured torque in various rotational rheometer geometries, which apparently simply adds to the torque from the pure bulk solution.

Preparation and rheological characterization of Chitosan-Gelatine@ZnO-Si nanoparticles

Chitosan (Chi) and gelatine (Gel) polymer blends with ZnO nanoparticles loaded on silica were synthesized through a simple solution method under ultrasonic irradiation at different concentration ratios (5:3, 1:3 and 3:5). The viscosity characteristics of the nanostructure were investigated by using ultrasound irradiation to determine the behaviour of macromolecules in solution. Rheological characterization of the nanoparticles was determined. The experimental viscosity of the nanosystems was calculated with five different models including Huggins, Kraemer, Tanglertpaibul-Rao, Higiro and Rao. The results showed that the Huggins model was the best model for intrinsic viscosity determination of nanostructures at different concentration ratios and at sonicated or non-sonicated conditions. The voluminosity (VE) and the shape factor (υ) were calculated for the nanosystems. The Krigbaum and Wall parameter (Δb) along with the Chee parameter (μ) were calculated to understand the miscibility behaviour. The miscibility criterion was slightly affected by the collapse and cavitation. The intermolecular interactions occurring between polymers were investigated by comparing the experimental and ideal intrinsic viscosity. Characterization of the nanostructures was carried out via Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques.

Intrinsic Viscosity Determination of High Molecular Weight Biopolymers by Different Plot Methods. Chia Gum Case

The chia (Salvia hispanica) generates an abundant and viscous mucilage, this is purified with periods of heating-cooling and finally precipitated with ethanol, obtaining chia gum, CG. In this work the intrinsic viscosity is determined by different methods being Huggins taken as standard. The different methods are compared and evaluated with their respective percentage relative errors. By means of intrinsic viscosity is determined the molecular weight with value of 3846000g/mol. This polysaccharide acquires rod-like conformation with an a value, Mark-Houwink parameter, of 0.803 according to Int. J. Biological Macromol. 81 (2015) 991-999. This macromolecule is very promising and has potential in several industrial applications such as film forming, gel, thickener, and coemulsifier.

PROCEDURE FOR DETERMINATION OF THE MOLECULAR WEIGHT OF CHITOSAN BY VISCOMETRY

The aim of this publication is to facilitate the estimation of chitosan molecular weight (MW) in laboratories with no access to sophisticated analytical instruments, by applying the easily accessible and economical capillary viscometry. The procedure of viscosity-average molecular weight (Mv) determination is described in details. The examples provided encompass testing of the experimental procedure for determination of the Mv of chitosan with a low-molecular weight of 7.7 kDa and 88 kDa, after verification with a high-molecular weight polymer (477 kDa). The experimental work demonstrated the importance of the initial concentration of low-MW chitosan for the accurate determination of intrinsic viscosity and, as a consequence, the viscosity-average molecular weight.

KINETIKA DEGRADASI SELULOSA ASETAT DARI SABUT PINANG

Cellulose Acetate is a material with wide range in applications. Cellulose acetate may obtain from natural resources, such as areca fiber. Polymers should have uniform molecular weight for the applications and could be modify by ultrasonic waves. Ultrasonic treatment on polymer entangled with polymer degradation. In this research, degradation kinetics of cellulose acetate in acetone had been studied. Analysis was performed by determination of intrinsic viscosity in polymer solution system. Intrinsic viscosity was successfully obtained by fitting data using Huggins equation, indicate molecular interaction in polymer solution should not be neglected. Increasing in sonication time reducing the intrinsic viscosities as well as molecular size in solutions. Degradation rate constant and reaction order were obtained 5,975x10-3(g.mL-1)0,1.min-1 and 1,0616, respectively. Kinetics model was successful to determine the degradation rates of cellulose acetate on acetone by correlation coefficient (R2) at 0,966.

Ultrasound assisted polyacrylamide grafting on nano-fibrillated cellulose

Polyacrylamide has been grafted onto nanofibrillated cellulose (NFC-g-PAM) under mild conditions. This was accomplished by developing and optimizing an ultrasound assisted protocol in the presence of potassium persulfate initiator. The synthesis was optimized on the basis of maximizing grafting percentage and grafting efficiency by varying the initiator and monomer concentration. The data shows that ultrasound has a profound effect in promoting the grafting of PAM onto NFC. The intended grafting was confirmed and the properties of the new co-polymers were examined by elemental analyses, Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Intrinsic viscosity determinations in 0.1M cupriethylenediamine solutions for the NFC-g-PAM copolymers and the starting NFC and PAM homopolymer revealed that grafting of PAM onto nanofibrillated cellulose has a profound effect on the hydrodynamic characteristics of the graft polymers.

Solubilisation of Persian gum: Chemical modification using acrylamide

Persian gum (PG), mountain almond tree (Amygdalus scoparia) exudate, is a transparent and natural edible gum which consists of soluble (SFPG, 25–30wt%) and insoluble (IFPG, 70–75wt%) fractions. Therefore, in the present study, using response surface methodology (RSM), the influence of concentration (0.64–7.36wt%), acrylamide (0.070–0.120mol), temperature (19.77–70.23°C), and time (0.32–3.68h) on solubilizing and some other properties of IFPG were investigated. Based on our findings, the highest solubility (64wt%) was achieved at the presence of 6wt% IFPG, and 0.08mol acrylamide at 60°C after 3h. Intrinsic viscosity and molecular weight determination also confirmed modification reaction which led to reduction in molecular weight. In addition, the effect of pH and electrolytes on rheological properties showed that the soluble part of IFPG which modified at optimum conditions had an anionic structure similar to conventional SFPG.

Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

AbstractA set of hydrodynamic methods in extremely dilute solutions (determination of intrinsic viscosity [η], translational diffusion D and flotation in a centrifugal field s) was used in the studies of conformational properties, dimensions and equilibrium rigidity of individual molecules of a series of samples of poly(3‐hexylthiophene). Absolute molecular masses MsD were determined. The Mark–Kuhn–Houwink equations for the range of MsD from 2240 to 15 300 g mol−1 are given. For the first time, an analysis of conformational properties and equilibrium flexibility of poly(3‐hexylthiophene) molecules was carried out using the model of a statistical segment containing a twisted polymer chain. © 2017 Society of Chemical Industry

Opuntia dillenii (Ker-gawl) haw fruit peel pectin: Physicochemical, rheological, and functional behavior

High methoxyl low molecular weight pectin was extracted from Opuntia dillenii fruit peel under three acidic media. The effect of extraction medium on the yield and quality characteristics of pectin was investigated. The extracted samples consisted preponderantly galacturonic acid (68.2–74.0%) with minor quantities of neutral sugars viz., galactose (10.2–12.4%), arabinose (4.4–5.4%), and rhamnose (0.9–3.2%). DE (degree of esterification) of pectin samples estimated by FTIR ranged from 63% to 85%. The rheological properties of pectin showed decreased viscosity with increasing shear rate resulting in shear thinning flow features. Determination of intrinsic viscosity (1.4–3.5 dL/g) and molecular weight (21–76 kDa) showed significant differences among the extracted samples. All the samples were nonsticky, good flow ability, exhibited good functional properties like emulsion capacity and stability. The study advocates O. dillenii fruit peel as a source of high methoxy pectin for use in food and food allied industries. Practical applications The isolation of pectin from Opuntia dillenii pear peel with different extraction media was investigated to evaluate its quality with respect to yield and functional properties. CAP (Citric acid extracted pectin) was found to be HMP, higher yield with low ash content thereby enhancing the functional properties. Besides, it promotes the use of the underutilized, cactus crop as a source of pectin that can substitute other commercial HMP pectin used in food and pharmaceutical industries.

Using full‐factorial design analysis and response surface methodology to better understand the production of cationized chitosan from epoxides

AbstractThe production of cationized chitosan derivatives via reaction between chitosan and quaternary epoxides has the advantage of producing substances with a better regioselectivity and with structures that do not change as a function of pH, unlike N,N,N‐trimethylchitosan. Moreover, this reaction allows the production of cationized derivatives having different hydrophobic/hydrophilic balances because quaternary epoxides with different alkyl chains can be used in this reaction. The effects of reaction parameters, namely time, temperature and glycidyltrimethylammonium chloride (GTMAC)/chitosan (Ch) molar ratio, on the structural and hydrodynamic characteristics of N‐(2‐hydroxy)propyl‐3‐trimethylammoniumchitosan chloride (ChCat) and on reaction yield were evaluated using chemometrics and response surface methodology (RSM). Structural characterization and determination of intrinsic viscosity were realized using spectroscopic techniques (Fourier transform infrared and 1H NMR) and capillary viscometry, respectively. The polynomial functions and RSM developed from 23 full‐factorial analysis show the influence of the reaction parameters on the characteristics and properties of the ChCat produced, permitting the choice of appropriate reaction conditions to suit its desired application. Results show, as an example, that when the N‐substitution is carried out for 6 h at 50 °C employing excess of GTMAC (GTMAC/Ch = 4:1), water‐soluble moderately substituted ( = 33.0%) ChCat ([η] = 293.4 mL g−1) can be produced with moderate reaction yield (30.9%). Furthermore, as GTMAC is the simplest quaternary epoxide, the study of its reaction with chitosan serves as a template for more complex quaternary epoxides as they may be used for the production of new cationized chitosan derivatives possessing alkyl chains with various chain lengths. © 2016 Society of Chemical Industry

Dilute solution properties of canary seed (Phalaris canariensis) starch in comparison to wheat starch

Dilute solution properties of an unknown starch are important to understand its performance and applications in food and non-food industries. In this paper, rheological and molecular properties (intrinsic viscosity, molecular weight, shape factor, voluminosity, conformation and coil overlap parameters) of the starches from two hairless canary seed varieties (CO5041 & CDC Maria) developed for food use were evaluated in the dilute regime (Starch dispersions in DMSO (0.5g/dl)) and compared with wheat starch (WS). The results showed that Higiro model is the best among five applied models for intrinsic viscosity determination of canary seed starch (CSS) and WS on the basis of coefficient of determination (R2) and root mean square error (RMSE). WS sample showed higher intrinsic viscosity value (1.670dl/g) in comparison to CSS samples (1.325–1.397dl/g). Berry number and the slope of master curve demonstrated that CSS and WS samples were in dilute domain without entanglement occurrence. The shape factor suggested spherical and ellipsoidal structure for CO5041 starch and ellipsoidal for CDC Maria starch and WS. The molecular weight, coil radius and coil volume of CSSs were smaller than WS. The behavior and molecular characterization of canary seed starch showed its unique properties compared with wheat starch.

Solution properties of a heteropolysaccharide extracted from pumpkin (Cucurbita pepo, lady godiva)

A water-soluble galactoglucofucomannan was extracted from pumpkin (Cucurbita pepo, lady godiva variety). GC–MS analysis indicated that the polysaccharide was composed of 1,6-linked-glucosyl, 1,2,6-linked-mannosyl, 1,3,6-linked-mannosyl, 1,2,6-linked-galactosyl, 1,2,6-linked-galactosyl, terminal fucosyl and terminal glucose. The solution properties of the polysaccharide were studied systematically by using size-exclusion chromatography combined with multi-angle laser light scattering, viscometry and dynamic light scattering at 25°C. The weight average molecular masses (Mw), intrinsic viscosity [η], radius of gyration (Rg) and hydrodynamic radius (Rh) were found to be 12.7×105g/mol, 780ml/g, 68nm and 116nm, respectively. The fraction dimension and value of ρ (Rg/Rh) of the polysaccharide revealed that it existed in a sphere-like conformation in distilled water. The dependence of zero shear specific viscosity on the coil overlap parameter was analyzed using different models. Furthermore, degradation of samples upon autoclaving has been observed and quantified by intrinsic viscosity determination and SEC-MALLS.

Rheological and kinetic study of the ultrasonic degradation of locust bean gum in aqueous saline and salt-free solutions

The ultrasonic degradation of locust bean gum (LBG) in aqueous solutions has been studied at 25°C for ultrasonication times up to 120min. Although LBG is not a polyelectrolyte, the degradation extent and kinetics were found to be somewhat sensitive to the ionic conditions in solution, and this is attributed to changes in molecular conformation that can occur in different salt environments. Ultrasonic degradation was tracked by rheological measurements that lead to the determination of intrinsic viscosity for the LBG molecules. A kinetic model was also developed and successfully applied to characterize and predict the degradation results.

Introduction of a reliable method for determination of intrinsic viscosity for any polymer with high precision

Intrinsic viscosities for a given polyelectrolyte in salt free and low-salt solvents reported in literatures are normally not comparable, because of inadequate valuation procedures. This article describes a theoretically justified reliable method, which is free of any model assumptions: The so called Wolf plot (logarithm of the relative viscosity as a function of polymer concentration) enables the unequivocal determination of intrinsic viscosities for all kinds of macromolecules, irrespective of whether they are chain molecules of different architecture or globular polymers, whether they are charged or uncharged. The validation of the method was examined by evaluation of the viscosities of a polyelectrolyte, some uncharged polymers of different architectures, uncharged polymer blends, and some literature data.

Mechanical and thermal properties of dimer acid based nylon 636/Nylon 66 copolymers

ABSTRACTDimer acid (DA)‐based nylon 636/nylon 66 copolymers were synthesized by in situ polymerization. The effects of incorporating nylon 66 on the mechanical and thermal properties were characterized by means of intrinsic viscosity determination, attenuated total reflection (ATR)–Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry, thermogravimetric analysis, and mechanical testing. The results show that the intrinsic viscosity of the copolymers ranged from 1.0 to 2.1 dL/g, depending on the content of nylon 66. The incorporation of nylon 66 into DA‐based nylon 636 had no significant effect on the values of the glass‐transition temperature, melting temperature, temperature at 50% weight loss, or temperature at the maximum rate of decomposition, but the crystallization temperature, crystallinity degree, and extrapolated onset temperature increased. ATR–FTIR spectroscopy and XRD demonstrated that with increasing nylon 66 mass, the content of α‐ and β‐crystal forms would increase accordingly. The mechanical test data revealed that with increasing nylon 66 concentration, the tensile strength of the copolymers increased, and the flexural strength and flexural modulus first increased and then decreased. However, the notched Izod impact strength decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39845.

Effect of the oxidation level of corn starch on its acetylation and physicochemical and rheological properties

The objective of work was to determine the effect of the oxidation level of corn starch on its susceptibility to acetylation and to compare the physicochemical and rheological properties of the modified starches obtained. Starch was oxidised by sodium hypochlorite in amounts equivalent to 10, 20 and 40g Cl/kg starch (oxidation level I, II and III), and then acetylated using acetic anhydride. To assess the effectiveness of the oxidation and acetylation processes, the carboxyl and carbonyl groups and acetyl groups, respectively, were determined in modified starches. The starches were also examined for water-binding capacity and water solubility at 50, 60, 70 and 80°C, and for susceptibility to retrogradation of 2% starch pastes. In addition, the thermodynamic characteristics of gelatinisation were established. Rheological studies included determination of intrinsic viscosity, pasting characteristics by RVA, and mechanical spectra of starch gels. The results showed that oxidation level influences the effectiveness of starch acetylation and the physicochemical and rheological properties of starch investigated in this study.

SYNTHESIS, CHARACTERIZATION, AND IN VITRO DEGRADATION OF POLY(LACTIC ACID) UNDER PETROLEUM PRODUCTION CONDITIONS

Poly (d,l-lactic acid), PLA, was synthesized from lactic acid using two polymerization methods: direct polycondensation and ring opening polymerization. The effects of temperature, reaction time, and catalyst type were studied. Intrinsic viscosity determination, differential scanning calorimetry, and infrared spectrometry were used to characterize the polymers obtained. Gravimetric and colorimetry analyses were used to study polymer degradation under different environments varying pH, temperature and salinity. The results showed that higher rates of degradation were obtained in higher pH and temperatures, and lower molar mass polymers presented a higher degradation rate. The outcome showed that it is possible to control the degradation rate under different petroleum production conditions. This makes the PLA a potential material to be used as a matrix for additives releasing systems.