Dilute Solution Properties Research Articles

Volumetric properties of dilute (d-glucose + H2O) solutions at temperatures from (293.15 to 433.15) K and pressures from (0.10 to 50.00) MPa

Abstract The densities of aqueous solutions of d -glucose were measured at temperatures from (293.15 to 433.15) K and pressures from (0.10 to 50.00) MPa using a vibrating-tube densimeter. Apparent molar volumes Vφ,m and partial molar volumes at infinite dilution V∞ were calculated from the experimental results. V∞ increases as temperature increases and varies linearly with temperature above ∼300 K. In addition, V∞ does not vary as a function of pressure up to 50.0 MPa. Comparison of these results with previous studies indicate excellent agreement and significantly extend the experimental database for aqueous solutions of d -glucose to elevated temperatures and pressures.

Pseudo-laminarization effect of dilute and ultra-dilute polymer solutions on flows in narrow pipes

The properties of dilute and ultra-dilute polymer solutions flowing in a narrow pipe (inner diameter: 680, 400, and 125 μm) were evaluated experimentally by measuring the pressure drop at constant flow rate. Deionized water, silicone oil, and several aqueous solutions of polyacrylamide (PAA), polyethylene oxide (PEO), and xanthan gum (X-Gum) were used. In viscosity measurements, 100- and 10-ppm solutions exhibited non-Newtonian viscosities whereas 1-ppm solutions exhibited Newtonian viscosities. We applied a power-law model to the non-Newtonian viscosities and estimated a generalized Reynolds number. Moreover, we focused on the transition and turbulent regions because the flows being observed were through narrow pipes. For water and silicone oil, good agreement was obtained between the resultant pressure drop and the predicted value. Furthermore, the critical Reynolds number for water and silicone oil was approximately 1.8×103. In contrast, laminar flow was maintained in the transition region for the dilute and ultra-dilute polymer solutions. In the 125- μm capillary flows, the maximum critical Reynolds numbers for the ultra-dilute polymer solutions were 2.4×103 (PAA), 3.9×103 (PEO), and 3.0×103 (X-Gum). Even though ultra-dilute solutions were used, pseudo-laminarization was obtained. To understand the experimental results, we estimated the first normal stress difference. All such values were correlated with the wall shear rate. We conclude that the pseudo-laminarization can be associated with the elasticity of the polymer solutions and is typified by the appearance of strong elastic properties in small-scale flows.

Study of the Topological Structure of Bamboo Bambusa sp. Lignin Macromolecules

The topological structure of macromolecules of Pepper lignin isolated from bamboo stems is studied. The molecular properties of dilute lignin solutions in dimethylformamide are investigated by the methods of high-velocity sedimentation, translational diffusion, and viscometry. The molecular mass of fractions, the scaling coefficients of the Kuhn–Mark–Houwink equation, and the Tsvetkov–Klenin hydrodynamic invariant are determined. It is first shown that the lignin of bamboo stems belongs to the universal class of chaotically branched polymers, and the degree of branching of macromolecules is estimated.

The Influence of Molecular Packing on the Emissive Behavior of Pyrene Derivatives: Mechanoluminescence and Mechanochromism

AbstractAlthough some bright, organic mechanoluminescence (ML) luminogens with aggregation‐induced emission properties and twisted molecular structures are recently reported, those with planar structures and bright ML and their related effective design strategies are not yet explored, partially due to aggregation‐caused quenching in luminogens with planar structures. Herein, using the unique solid‐state packing style of pyrene, bright dual monomer‐excimer‐ML and excimer‐ML from two pyrene derivatives (Py‐Bpin and Py‐Br) with a simple, planar molecular structure are reported for the first time, and two analogs of pyrene and Py‐H are used for comparison. These four luminogens display similar optical properties in dilute solution but different luminescent properties in the solid state, mainly due to their different molecular packing. Interestingly, pyrene is mechanochromism (MC)‐ and ML‐inactive, while Py‐H is MC‐active, Py‐Bpin is MC‐ and ML‐active, and Py‐Br is ML‐active. The relationship between molecular packing and ML/MC properties is confirmed by analyzing single‐crystal structures and related experimental results, providing important information to further understand the mysterious ML process and opening a new way to design efficient luminogens with both MC and ML.

Semiflexible ring polymers in dilute solutions

Our recent theoretical and/or Monte Carlo results for dilute solution properties of semiflexible ring polymers on the basis of the wormlike ring model are briefly summarized. The behavior of the mean-square radius of gyration 〈S2〉, intrinsic viscosity [η], scattering function P(k) with k the magnitude of the scattering vector, and second virial coefficient A2,Θ at the Θ state is examined as a function of the reduced contour length λL, where λ−1 and L are the stiffness parameter and contour length of the wormlike ring, respectively. Effects of the topological constraints on 〈S2〉, [η], P(k), and A2,Θ of semiflexible rings are also examined by comparing the results for the wormlike rings without the topological constraints with those for the wormlike ring of the trivial or trefoil knot.

Salt effects on the dilute solution properties of bototo gum (Cochlospermum vitifolium)

<p><span style="line-height: 113%; font-family: 'Times New Roman',serif; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'; mso-font-kerning: 14.0pt; mso-contextual-alternates: yes; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">Salt effects on the dilute solution properties of bototo gum (<em>Cochlospermum vitifolium</em>) were investigated. There were measured the intrinsic viscosities of the polymer under study in water, in NaCl (at different concentrations) and in NaCl, CaCl<sub>2</sub> and AlCl<sub>3</sub>, at the same ionic strength (I = 1), using an Ubbelohde viscometer at 25°C. The Huggins intersection model (R<sup>2</sup>) is more appropriate to determine the intrinsic viscosity than the Kraemer's equation. This parameter tends to reduce with the increase in the salt concentration and the cation charge. The molecules of <em>C. vitifolium</em> gum exudate in water (solvent Φ) tend to adopt a “random coil” conformation, of great volume and radius, which exist in two regimes: diluted and semi-diluted; in the presence of salts, the coils exist only in a diluted regime where they are separate each other. The macromolecules in water have probably an extended ellipsoid shape but in presence of salts, they change to another more compact, probably spherical, with radii and smaller volumes. The knowledge of the behavior of <em>C. vitifolium</em> gum molecules in dilute solutions is an important criterion for its rational use in various industries</span></p>

Magnetorheological and Volumetric Properties of Starch and Polyethylene Glycol Solutions in the Presence of NiO Nanoparticles

The effect of NiO nanoparticles on the rheological and volumetric properties of dilute solutions of starch-NaOH-H2O, PEG400-PEG2000 and PEG400-PEG6000 were investigated. Achieve this aim requires to prepare the stable nanofluids. Therefore, nanoparticles of NiO were added to these solutions and dispersed by a shaker and an ultrasonic bath for making the homogeneous nanofluids. The UV-Vis spectroscopy, zeta potential and dynamic light scattering have been used to specify the stability and particle size distribution of colloidal solutions studied. Fluid flow and suspense structure of NiO nanoparticles in the solutions of starch-NaOH-H2O, PEG400-PEG2000 and PEG400-PEG6000 were studied by measuring the magnetorheological properties at T=298.15 K. Bingham plastic, Herschel-Bulkley and Carreau-Yasuda models have been applied for modeling the magnetorheological properties of nanofluids. Density values of NiO-starch-NaOH-H2O, NiO-PEG400-PEG2000 and NiO-PEG400-PEG6000 nanofluids have also been measured at T = (298.15, 308.15 and 318.15) K. The excess molar volumes were calculated from the density data for highlighting the interparticle interactions occurred in nanofluids. Singh et al. equation was used for fitting the excess molar volume values.

Study on the effects of sucrose and lactose on the rheological properties of Alyssum homolocarpum seed gum in dilute solutions

Nowadays, demands for hydrocolloids which improve the rheological properties of foods as well as retain their properties under the influence of food additives have increased. In this study, dilute solution properties were employed to understand the molecular and conformational properties of Alyssum homolocarpum seed gum (AHSG), in presence of sucrose and lactose. The model of Tanglertpaibul & Rao was selected as the best model for the estimation of the intrinsic viscosity. It was shown that except for water, the solutions of sucrose and lactose are poor solvents for AHSG as indicated by a decrease in intrinsic viscosity, swollen specific volume, shape function, and coil dimensions. As the sucrose and lactose concentrations increased, the coil radius decreased. The reduction in the shape and swollen volume parameters in the presence of sucrose and lactose as compared to the sugar-free solution indicated the negative effect of the opted sugars on the molecular volume of the gum. Evaluations of the dilute solution properties of the gum in sucrose and lactose solutions revealed that the existence of a conformation tending to ellipsoidal shape and the probability of the conformation of random coil with no molecular entanglements in AHSG solutions.

Dilute Solution Properties of Two Hairless Canary Seed Starches Compared with Wheat Starch in a Binary Solvent: Influence of Temperature, Mono‐ and Divalent Cations

The dilute solution properties of starches from two canary seed varieties (C05041 and CDC Maria), as well as wheat starch (WS) in DMSO/H2O (9/1 v/v %) solution, as a function of salt type (NaCl and CaCl2) and salt concentration (5–100 mM) at different temperatures (25, 35, 45, and 55 °C) are investigated. Various models, i.e., Huggins, Kraemer, Higiro, and Tanglertpaibul and Rao equations are applied for estimating the intrinsic viscosity [η] of the canary seed starches (CSSs) and WS in dilute solution. Of all the examined models, the Higiro 1 model shows a higher performance for determining the intrinsic viscosity of the selected starches at all temperatures and ionic strengths. The intrinsic viscosity [η] of the selected starches decreases significantly with an increase in ionic strength, at all examined temperatures. The results show that the influence of NaCl on the [η] reduction of CDC Maria starch and WS is more than for C05041 starch. The shape functions of the selected starches at 25 °C are spherical; however, with increasing ionic strength and temperature from 25 to 55 °C, the CSSs and WS samples take an ellipsoidal shape. The Berry number and the slope of the master curve reveal that CSSs and WS solutions at all temperatures and salt concentrations are in the dilute domain and no molecular entanglements occur.

Effect of temperature, ion type and ionic strength on dynamic viscoelastic, steady-state and dilute-solution properties of Descurainia sophia seed gum

In this study, dilute solution, steady state and dynamic rheological properties of Descurainia sophia seed gum (DSSG) were investigated. With increasing the solution temperature, the intrinsic viscosity and coil dimension of DSSG decreased. The intrinsic viscosity of DSSG was essentially constant over a very extensive range of ion concentrations. Activation energy and chain flexibility of DSSG were found to be 1.1 × 107 (J/kg) and 1353 (1/K), respectively. DSSG can be introduced as good encapsulator in food and pharmaceutical systems due to low degree of chain flexibility. Steady shear measurements showed shear thinning behavior at all tested temperatures, regardless of ion type and ionic strength. Addition of NaCl and increasing temperature caused a decrease in consistency coefficient and an increase in the flow behavior index. On the other hand, at high CaCl2 concentration, the consistency coefficient of DSSG increased. The values of tan δ in all tested conditions were lower than one, but more than 0.1, revealing weak gel-like behavior. The frequency sweep results revealed that DSSG solution had weak gel behavior at different ions types and ionic strengths: as dynamic moduli increased with increasing frequency and G′ was always superior to G″. The data obtained in the present study and the results thereof can be useful when considering the impact of salts, and/or processing parameter such as temperature on food systems.

Effect of temperature and selected sugars on dilute solution properties of two hairless canary seed starches compared with wheat starch

In this paper, influence of temperature (25, 35, 45 and 55°C) and sugars (sucrose and lactose) at different concentrations (0, 5, 10 and 15%) on some molecular parameters of starches from two canary seed varieties (C05041 and CDC Maria) in the dilute regime were investigated in comparison to wheat starch (WS). The results indicated that the intrinsic viscosity ([η]) values of C05041, CDC Maria and WS samples were 1.42, 1.46 and 1.70dl/g at 25°C, respectively. Intrinsic viscosity of selected starches decreased with an increase in temperature, but the effect of high temperatures were somewhat unnoticeable. By increasing the sugar concentration, intrinsic viscosity of each starch solution significantly decreased in comparison with the value determined for sugar free solution. Lactose had more pronounced effect on the intrinsic viscosity reduction of CDC Maria starch and WS at 25°C and 35°C compared with sucrose (P<0.05). But at 55°C, the effect of increasing sucrose on decreasing of [η] of CDC Maria and WS samples were more considerable. The shape factor of starch samples at 25°C were spherical, but increasing temperature from 25°C to 55°C, CSSs and WS samples took an ellipsoidal shape.The interaction between starches and solvent/cosolutes is the predominant factors determining their functional properties in food systems. One of the aspects can help to understand the characteristic of biopolymers such as starches is determination of their dilute solution properties as a function of common additives which are used in food systems. As a matter of fact, dilute solution properties can help to understand the potential applications of biopolymers in food and non-food application. Attentively, dilute solution properties would give some priceless information about molecular properties, biopolymer behavior and its interaction with copolymers. For instance, intrinsic viscosity provides deep insight into fundamental properties of the solute and its interaction with the solvent and/or cosolutes, conformation of flexible chains. There are many studies which investigated the effect of different parameters such as temperature, salts and sugars on dilute solution properties of hydrocolloids, especially gums. Regrettably, few researches scrutinized the influence of various cosolutes on dilute solution properties of starch. Then in this paper, we studied the dilute solution properties of starches from two canary seed varieties (C05041 and CDC Maria), as a new potential source of starch, (CSSs), in comparison to wheat starch at different experimental conditions (temperatures and sugars at different concentrations) in order to shed light on its behavior in real system in comparison to wheat starch. Because of the unique properties of wheat starch, comparison of canary seed starch with wheat starch in dilute regime can help to having better vision of this new starch source. Overall, the intrinsic viscosity, coil dimensions (Rcoil and Vcoil), swollen specific volume, shape function, and hydration parameter of selected starches were determined affected by temperature and sugars concentration treatments. The importance of these results will be cleared when taking into account the influence of crucial additives generally used in food systems, for instance, different sugars and/or frequent processing parameters such as temperature on rheological and functional properties.

A comprehensive molecular dynamics study of a single polystyrene chain in a good solvent

In this study, molecular characteristics of polystyrene (PS) was calculated measuring its dilute-solution properties in toluene at 288.15 K via molecular dynamics (MD) simulations. The solution models consisted of PS chains with different number of repeating units all of which were in a dilute regime. In order to investigate the compatibility between the polymer and the solvent molecules, interaction energy and Flory-Huggins (FH) interaction parameter were estimated. The simulation results indicate that increasing the chain repeating units enhanced the interaction between the solute and the solvent. Additionally, the chain dimensions were evaluated calculating the radius of gyration (Rg) and end-to-end distance, r0. To determine the dynamic behavior of the chains in the solutions, mean square displacement (MSD) and diffusivity coefficient were calculated. The simulation results indicated that the chain rigidity at low molecular weight and chain flexibility with increasing the molecular weight influenced chains dynamic behavior and diffusivity. Moreover, radial distribution function (RDF) illustrated the effect of steric hindrance of the chains in dilute solution on capturing the solvent molecules. In addition, solution viscosity was calculated by performing non-equilibrium molecular dynamics simulation (NEMD). The obtained results of chain characteristics and viscosity showed a good agreement with experimental results published previously. This agreement confirms the accuracy of the applied simulation method to characterize the dilute solutions and the chains characteristics.

Solution properties, unperturbed dimensions, and chain flexibility of poly(1‐adamantyl acrylate)

ABSTRACTPoly(1‐adamantyl acrylate) (PAdA) exhibits much higher glass transition and degradation temperatures than other polyacrylates. However, the quantitative evaluation of the stiffness of this polymer chain has not been reported previously. In this study, the dilute solution properties and conformational characteristics of PAdA were evaluated using viscometry and scattering techniques. The unperturbed dimensions of this polymer were evaluated using the Burchard–Stockmayer–Fixman extrapolation and the touched‐bead wormlike chain model. The PAdA chain has a comparable persistence length, diameter per bead and characteristic ratio to poly(methyl methacrylate) and polystyrene. All these results indicate that PAdA is less flexible than common polyacrylates. In addition, the second virial coefficients (A2) of PAdA in different solvents obtained by static light scattering were compared. Among the solvents investigated, tetrahydrofuran is a moderate solvent. Radius of gyration of a polymer sample in the various solvents ranged from 16.8 to 30.3 nm. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1526–1531

Effect of sodium hydroxide on the interactions of polyethylene glycol macromolecules with water molecules

The rheological properties of dilute water solutions of polyethylene glycols with different molecular mass (1000, 3000, 6000, 8000, 20,000) were investigated in the temperature range 293-323°K in the presence of sodium hydroxide (0.1 mol/l). The intrinsic viscosities, Huggins constants, mean-square distance between the ends of the macromolecular chain, crossover concentrations and activation energies of viscous flow have been determined vs. temperature and molecular mass of polymers. It has been established that the macromolecular coils in the presence of sodium hydroxide (0.1 mol/l) in aqueous solutions of polyethylene glycols accept the unperturbed state as in theta solutions and the intrinsic viscosity becomes very sensitive to the molecular mass of polymers. The new approach for estimating the interaction energy per volume fraction between the macromolecule and solvent molecule has been proposed.

Thermodynamic properties of dilute Co-Fe solid solutions studied by 57Fe Mössbauer spectroscopy

Abstract The Co1-xFex alloys where x ranges from 0.01 to 0.06 were measured at room temperature using transmission Mössbauer spectroscopy (TMS). The analysis of the obtained data allowed the determination of the short-range order (SRO), the binding energy Eb between two iron atoms in the studied materials using the extended Hrynkiewicz-Królas idea and the enthalpy of solution HCo-Fe of Fe in Co. The results showed that the Fe atoms dissolved in a Co matrix interact repulsively and the estimated value of HCo-Fe = -0.166(33) eV/atom. Finally, values of the enthalpy of solution were used to predict the enthalpy of mixing for the Co-Fe system. These findings were compared with corresponding data given in the literature, which were derived from calorimetric experiments and from the cellular atomic model of alloys described by Miedema.

Topology-Dependent Chain Stiffness and Local Helical Structure of Cyclic Amylose Tris(3,5-dimethylphenylcarbamate) in Solution

Conformational properties of rigid and semiflexible cyclic chains are still unclear owing to few experimental researches on dilute solution properties. Five cyclic amylose tris(3,5-dimethylphenylcarbamate) (cADMPC) samples ranging in the weight-average degree of polymerization from 23 to 150 were prepared from enzymatically synthesized cyclic amylose. Light scattering and small-angle X-ray scattering measurements were made on the samples to determine the weight-average molar mass Mw, the particle scattering function P(q), and the z-average mean-square radius of gyration ⟨S2⟩z in methyl acetate (MEA), 4-methyl-2-pentanone (MIBK), and tetrahydrofuran (THF) at 25 °C. The obtained P(q) and ⟨S2⟩z data were analyzed on the basis of the cyclic wormlike chain model to determine the wormlike chain parameters, that is, the helix pitch (or helix rise) per residue h and the Kuhn segment length λ–1 (the stiffness parameter or twice of the persistence length) as a function of Mw. Although the chain stiffness parameter ...

Dynamics of falling droplet and elongational properties of dilute nonionic surfactant solutions with drag-reducing ability

The dynamics of the falling droplet through a nozzle for dilute nonionic surfactant (oleyl-dimethylamine oxide, ODMAO) aqueous solutions with viscoelastic and drag-reducing properties were investigated at different concentrations of ODMAO solutions Cs = 500, 1000, and 1500 ppm by weight. The effects of the flow rate and tube outer diameter on the length of the filament, which was the distance between the tube exit and the lower end of a droplet at the instant when the droplet almost detached from the tube, were clarified by flow visualization measurements by a high-speed video camera. Two types of breaking-off processes near the base of the droplet and within the filament were classified by the Ohnesorge number Oh and the Weber number We. In the regime of the higher Oh and We, the length of the filament became drastically larger at Cs = 1000 and 1500 ppm, whose high spinnability represented the strong viscoelasticity of ODMAO solutions. In the case where the filament was broken up near the lower end of the neck and thinning in time, the thinning of the diameter of the filament was measured by a light-emitting diode micrometer. As for the elasto-capillary thinning of dilute nonionic surfactant solutions, the initial necking process was similar to that of Newtonian fluids and then followed the exponential thinning like polymer solutions. The apparent elongational viscosity of the dilute nonionic surfactant solution was evaluated in the elasto-capillary thinning regime, in which the elongation rate was almost constant. At Cs = 1000 and 1500 ppm, the Trouton ratio, which was the ratio of the apparent elongational viscosity to the shear viscosity, was found to be several orders of magnitude larger than that of Newtonian fluids, while the shear viscosity measured by the capillary viscometer was almost the same order of the Newtonian fluids. The higher elongational property would be closely related to the higher drag-reducing ability of dilute nonionic surfactant solutions.

Effect of halogen bonding on supramolecular assembly and photophysical properties of diaryl oxalates

In order to determine the effect of halogen bonding on supramolecular assemblies and photophysical properties of diaryl oxalates, diaryl oxalate itself and its derivatives with fluorine, chlorine, bromine, and iodine substituents in the p-position of phenyl rings were studied and compared. Their single-crystal structures were studied by geometrical analysis and theoretical calculation. The study reveals that different halogen bonds are formed with respect to different halogen atoms, such as C…F and X…X (bromine and iodine atoms) interactions, and molecular stacking modes would be affected by halogen bonds directly. Comparative studies of photophysical properties in dilute solution and solid state indicate that halogen substitutions would not affect the emission processes of diaryl oxalates in dilute solution; this is not the case for their solid state. This work has demonstrated that halogen bonds play an important role in regulating structures and photophysical properties of diaryl oxalates.

Physicochemical properties of aqueous solutions of L-aspartic acid containing chitosan

Physicochemical properties of aqueous solutions of L-aspartic acid with and without addition of chitosan have been studied by conductometry, potentiometry, refractometry, tensiometry, and viscosimetry. It has been shown that aspartic acid molecules take a cyclic configuration stabilized by hydrogen bonds in aqueous solution at c > 0.04 g/dL (298 K). The interaction of chitosan with aspartic acid results in the formation of the polymeric salt that dissociates in aqueous solution to give chitosan polycation [~(NH3)+] and aspartate counterions. The addition of chitosan to solutions of L-aspartic acid results in progressive increase in the surface tension, absorbance, and refractive index as well as the change in hydrodynamic properties of the macromolecules. The polymeric salt exhibits polyelectrolyte properties in dilute aqueous solutions. The increase in temperature impairs the thermodynamic quality of the solvent for chitosan leading to the shrinkage of the polymer coils and, hence, to the decrease in the intrinsic viscosity of the system.

Dimensional and hydrodynamic properties of cellulose tris(alkylcarbamate)s in solution: Side chain dependent conformation in tetrahydrofuran

We prepared cellulose tris(ethylcarbamate) (CTEC), cellulose tris(n-butylcarbamate) (CTBC), and cellulose tris(n-octadecylcarbamate) (CTODC) samples with different molecular weight to determine their conformational properties in dilute solution. Weight average molar masses Mw,z-average mean-square radii of gyration 〈S2〉z, particle scattering functions P(q), and intrinsic viscosities [η] of the CTEC, CTBC, and CTODC samples in tetrahydrofuran (THF) at 25 °C were determined by size exclusion chromatography equipped with multi-angle light scattering detectors (SEC-MALS), small angle X-ray scattering (SAXS), and viscometry. Infrared (IR) absorption measurements were also made to observe intramolecular hydrogen bonding between C=O and NH groups. The obtained 〈S2〉z, P(q), and [η] data were analyzed in terms of the wormlike chain model to determine the Kuhn segment length (stiffness parameter, or twice of the persistence length) λ−1 and the helix pitch (rise) per residue h. While CTBC has the highest chain stiffness in the three cellulose derivatives as in the case of the corresponding amylose derivatives, the difference in the wormlike chain parameters is less significant for the cellulose alkylcarbamate derivatives. Indeed, intramolecular hydrogen bonding of CTEC, CTBC, and CTODC is weaker and fewer than that for the corresponding amylose derivatives owing to the main chain linkage, α or β.