Properties Of Aqueous Solutions Research Articles

Thermoresponsive Properties of Poly[oligo(ethylene glycol) sorbate]s Prepared by Organocatalyzed Group Transfer Polymerization

The current contribution presents the synthesis of poly[oligo(ethylene glycol) sorbate]s (PREGmSs) by the t-Bu-P4-catalyzed group transfer polymerization (GTP) method, their postpolymerization modification at the backbone double bond, and thermoresponsive properties in aqueous solution. Four oligo(ethylene glycol) sorbate monomers (REGmSs), including 2-(2-methoxyethoxy)ethyl sorbate (MeEG2S), 2-(2-(2-methoxyethoxy)ethoxy)ethyl sorbate (MeEG3S), 2-(2-(2-ethoxyethoxy)ethoxy)ethyl sorbate (EtEG3S), and 2-(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)ethyl sorbate (MeEG4S), are newly designed to study the thermoresponsive properties of their related polymers. The t-Bu-P4-catalyzed GTP of REGmS only proceeds in a 1,4-regioselective addition manner to quantitatively produce the backbone trans-rich (ca. 80%) PREGmS. The complete hydrogenation and epoxidation of the backbone double bonds result in hydrogenated and epoxidized polymers (PREGmS-H2 and PREGmS-epoxy, respectively), which have different main-chain structures and rigidity from their parent PREGmS. Given the 1,4-substituted structure of a sorbate monomer, the chemical structure determination of PREGmS-H2 by 13C NMR spectra demonstrates that the above polymers have an erythro-rich (ca. 60%) structure in diastereochemistry and a diisotactic/disyndiotactic ratio around 1:1 in stereoregularity. The thermoresponsive properties of PREGmS, PREGmS-H2, and PREGmS-epoxy in aqueous solutions are studied in detail from various aspects in terms of polymer mass concentration, molecular weight, length and end group of the oligo(ethylene glycol) side chain, and main-chain structure by turbidity, 1H NMR spectroscopy, and dynamic light scattering (DLS) methods, which are discussed below.

Synthesis and spectral properties of H acid-containing dyes and their Mannich-type dyeing performances on silk fibroin

The colouration of silk fibroin through a Mannich-type reaction with aromatic primary amine-containing dyes (APADs), named Mannich-type dyeing, is a novel dyeing method with the advantages of moderate conditions, high selectivity, and high wet fastness. In this study, three novel APADs, including an H acid structure, D1-D3, were designed and synthesized. A similar dye, C1, without an aromatic primary amine group, was selected as the control. Their spectral and colour fastness properties in aqueous solutions and on silk fabrics were measured and evaluated. In addition, their Mannich-type reactivity to silk fabric was evaluated via experiments and simulated calculations. It was revealed that for the H acid-containing dye with the same chromosome structure, the electron accepting/donating properties of the diazo and coupling components affect the colour of the dye after the Mannich-type dyeing. The substituent effect of dyes C1–D3 demonstrated that with the changing properties of electron donation and acceptance in the case of the diazonium component, the absorption spectrum (λmax) of the neutral aqueous dye solution changed from reddish-orange (505 nm) to bluish-violet (541 nm). The λmax of Mannich-type dyed fabrics was generally red-shifted in comparison with that of dyed fabrics by acidic dyeing, which implied the formation of a reactive bond between the dye and the silk fibroin. The presence of aromatic primary amine groups in dyes is the prerequisite for Mannich-type reactivity. The primary amine groups on both benzene and naphthalene rings have Mannich-type reactivity, which is related to the electron cloud density of amino N atoms. With the increase in electron cloud density of the amino N atom, the colour fixation of the dye and the fibre was improved. After the Mannich-type dyeing, the colour fastness of the dyed fabrics and DMF stripping resistance significantly improved, also indicating the formation of a covalent bond between the dye and the fibre. The simulated calculation predicted the colour of APAD in an aqueous solution and on dyed silk fabric after Mannich-type dyeing, which guides the design and enrichment of APADs’ chromatography.

Exploring dielectric spectra of polymer through molecular dynamics simulations

ABSTRACT In this work, poly(N-isopropylacrylamide) (PNIPAM) was used as a research object to explore the feasibility of molecular dynamics (MD) simulations to study the dielectric properties of polymers. A comparison of the static dielectric constants for two different calculation schemes, the applied electric field method and the dipole moment fluctuation method, has been conducted. The dielectric properties of PNIPAM aqueous solutions with different concentrations were studied as a function of temperature. The static dielectric constants derived from dipole moment fluctuation method at different temperatures can accurately describe the phase transition process. The concentration does not affect the lower critical solution temperature, but significantly affects the relaxation process of the system. According to the frequency-dependent dielectric constants, two relaxation processes are observed, namely, the dielectric relaxation process in the region of frequency less than 30 terahertz (THz) determined by the synergistic interaction of PNIPAM and water molecules, and that in the region of frequency higher than 30 THz mainly determined by water molecules beyond the solvation shell of the polymer. The calculation results suggest that the dielectric behaviour is concentration and temperature independent, similar to Debye behaviour of bulk water. This method of calculating dielectric properties using MD simulations can be used in detecting the dynamic processes of soft condensed matter and in aiding the design of materials with excellent dielectric properties.

Electrochemical Characterization of Ionic Dynamics Resulting from Spin Conversion of Water Isomers

Para- and ortho-isomers of water have different chemical and physical properties. Excitations by magnetic field, laser emission or hydrodynamic cavitation are reported to change energetic levels and spin configurations of water molecules that in turn change macroscopically measurable properties of aqueous solutions. Similar scheme is also explored for dissolved molecular oxygen, where physical excitations form singlet oxygen with different spin configurations and generate a long chain of ionic and free-radical reactions. This work utilizes electrochemical impedance spectroscopy (EIS) to characterize ionic dynamics of proposed spin conversion methods applied to dissolving of carbon dioxide CO2 and hydrogen peroxide H2O2 in pure water excited by fluctuating weak magnetic field in μT range. Measurement results demonstrate different ionic reactivities and surface tension effects triggered by excitations at 10−8 J/mL. The CO2- and O2-related reaction pathways are well distinguishable by EIS. Control experiments without CO2/H2O2 input show no significant effects. Dynamics of electrochemical impedances and temperature of fluids indicates anomalous quasi-periodical fluctuations pointing to possible carbonate-induced cyclic reactions or cyclical spin conversion processes. This approach can underlie the development of affordable electrochemical sensors operating with spin conversion technologies with applications in quantum biology, biophysics, and material science.

Cationic Polyelectrolytes Containing Perfluorinated Groups: Synthesis and Self-Assembly Properties in Aqueous Solutions

In this work, the synthesis and solution self-assembly of partially fluorinated cationic polyelectrolytes based on post-polymerization-modified poly(2-(dimethylamino) ethyl methacrylate), incorporating hydrophobic fluorinated groups along the polymer chain, is reported. The post-polymerization modification aims to establish amphiphilic characteristics and strong polyelectrolyte properties to the polymer. Therefore, the self-organization characteristics in aqueous media are expected to be affected. The poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) homopolymer precursor is synthesized using RAFT polymerization. A quaternization reaction on the amine side groups using heptadecafluoro-10-iododecane results in the poly((2-dimethylamino) ethyl methacrylate-co-quaternized heptadecafluoro-10-iododecane (2-dimethylamino) ethyl methacrylate) (PQFD) amphiphilic statistical copolymers. We intentionally study statistical copolymers in our research of DMAEMA-based polyelectrolytes as there are not many studies about such materials. We have also chosen the incorporation of highly hydrophobic perfluorinated groups to study the changes in the solution properties of the initial hydrophilic homopolymer. The successful synthesis is supported by size-exclusion chromatography (SEC), 1H-NMR, and FTIR experiments. The self-assembly of the copolymers in aqueous solutions along with the dependence of the properties of the resulting aggregates on the pH, temperature, and ionic strength of the solution are studied using light scattering methods (DLS, ELS) and fluorescence spectroscopy (FS). The structural characteristics of the aggregates depend on composition, solution preparation protocol and solution pH, and temperature.

Interaction between Highly Diluted Samples, Protein Solutions and Water in a Controlled Magnetic Field

We have previously shown that water incubated in a weak combined magnetic field (CMF) increased the production of reactive oxygen species (ROS) by neutrophils. Adding high dilutions (HD) of water into the same system resulted in a similar effect. HD of antibodies to interferon-gamma (HD Abs to IFNγ) were shown to emit electromagnetic radiation and affect hydrogen bond energies. Here, we aimed to evaluate the effect of HD of substances (donor) on the properties of aqueous solutions (acceptor). The donor and acceptor were incubated for 1 h in a controlled magnetic field so that the walls of the two cuvettes were in close contact. As a control, the acceptor was incubated under the same conditions but without the donor. An aliquot of the acceptor solution was then added to mouse neutrophils, and ROS levels were measured using luminol-dependent chemiluminescence assay. Joint incubation led to a 185–356% increase (p < 0.05) in ROS production, depending on the type of acceptor sample. The magnitude of the effect depended on the parameters of the magnetic field. In a CMF, the effect was strongest, completely disappearing in a magnetic vacuum or with shielding. These findings are important for understanding the physical mechanism of action of HD preparations, which opens up opportunities for expanding their practical applications.

Preparation and characterization of APTES-assisted Fe3O4/CNTs composites with high decontamination and high magnetic recovery capacity

In this paper, the magnetic carbon nanotubes (CNTs) adsorbents with good adsorption capacity were prepared via linking Fe3O4 nanoparticles and CNTs by γ-Aminopropyltriethoxysilane (APTES). The prepared specimens were characterized by field emission scanning electron microscopy (SEM), Energy Dispersive Spectromete (EDS), X-ray diffraction (XRD), Raman spectrometer and BET detection. The content of tartrazine in the adsorbed solution was detected by a UV-vis spectrophotometer. The results show that the granular Fe3O4 particles are uniformly distributed on the surface of the carbon nanotubes, and the composite characteristic peaks of CNTs and Fe3O4 are detected by XRD. The specific surface area, total pore volume and average adsorption pore size of Fe3O4/APTES/CNTs are 181.166m2/g, 2.109m3/g, and 44.582nm, respectively, and the equilibrium adsorption capacity for tartrazine is 25 mg/g. Fe3O4/APTES/CNTs had excellent dispersion property in aqueous solution, and could be attracted by magnetic force. So the magnetic CNTs adsorbents can be used in recycling and reuse by magnetic separation and thus have a huge application prospect.

Preparation of bioplastic consisting of salmon milt DNA.

The microplastic that pollutes the ocean is a serious problem around the world. The bioplastic consisting of biopolymers which is degraded in nature, is one of the strategies to solve this problem. Although the bioplastics consisting of protein, polysaccharide, polylactic acid, etc., have been reported, which consist of DNA, one of the most important materials in the genetic process, have not been reported to the best of our knowledge. In addition, a large amount of DNA-containing materials, such as salmon milts, is discarded as industrial waste around the world. Therefore, we demonstrated the preparation of a bioplastic consisting of salmon milt DNA. The DNA plastic was prepared by the immersion of a DNA pellet in a formaldehyde (HCHO) solution and heating. As a result, the water-stable DNA plastics were obtained at the HCHO concentration of 20% or more. Particularly, the DNA plastic with a 25% HCHO treatment showed water-insoluble, thermally stable, and highly mechanical properties. These are due to the formation of a three-dimensional network via the crosslinking reaction between the DNA chains. In addition, since DNA in plastic possesses the double-stranded structure, these plastics effectively accumulated the DNA intercalator, such as ethidium bromide. Furthermore, the DNA plastics indicated a biodegradable property in a nuclease-containing aqueous solution and the biodegradable stability was able to be controlled by the HCHO concentration. Therefore, salmon milt DNA has shown the potential to be a biodegradable plastic.

Stability and uniformity of gas–liquid two-phase flow in shear-thinning fluids in parallelized microchannels

The stability of gas–liquid two-phase flow and uniformity of bubble size in shear-thinning fluids within symmetrical parallelized microchannels are investigated experimentally. Air and sodium carboxymethyl cellulose (CMC) aqueous solutions with 0.3% SDS are used as the dispersed and continuous phases, respectively. The process of gas pressure buildup and rapid release is observed under conditions of exceeding the critical gas and liquid flow rates. Various slug bubble shapes are identified in different concentrations of CMC solutions, gas and liquid flow rates. The results show that the increase of liquid flow rates and the decrease of CMC concentration are beneficial for the stability of bubble formation and uniformity of bubble size in the parallelized microchannels. Finally, semi-empirical formulas are proposed, based on the rheological property of CMC aqueous solutions, to estimate the bubble length.

Studies of radial distribution function and second virial coefficient for surfactant decyltrimethylammonium bromide in aqueous solutions at 298.15 K: Evidence for cation–cation hydrophobic interactions effect

Excess internal pressure of solution and excess partial molar volume of solute data embedded in the parameter reversible isothermal work (W) have been used to calculate the ion–ion pair correlation functions (gij(r), r being distance) and the thermodynamic properties of aqueous solutions of decyltrimethylammonium bromide (C10TAB) in concentration range 0.01 – 0.14 mol∙kg–1. It is observed that gij(r) exhibits a peak at critical micelle concentration (cmc), while the virial coefficient term (gij(r) – 1) also goes through a maximum. Using Friedman's methodology and McMillan–Mayer theory of solutions, these results have been examined. With the help of concept of Gurney cosphere around the ions, the overlap of solvation shells (water molecules) as the concentration of ions increases have been used to probe water– structure effects as water–structure making/breaking. Coefficients Aij are estimated (Coulombic term, a core repulsive term, a cavity formation term and overlap of cosphere term) at various concentrations of ionic surfactant and at a radial distance of 20 Å for a micellar entity. Further analysis indicates that gij parameter (that is, representing cation–cation interaction g++) dominate over g+– (representing ion–solvent interaction) in solution phase. Thus for a self–assembly process (formation of micelle with aggregation number) in a solution phase is being characterized by a peak in gij(r) function at cmc and aggregation number of ≈ 38, area under the peak, while the virial coefficient variation indicates a dominance of cation–cation interaction and cosphere water–structural effects. It is emphasized that the approach adopted by us to use excess PV work to estimate gij(r) is better to understand the thermodynamic process involved in self–assemblies and micelle formation.

Quantum confined peptide assemblies in a visual photoluminescent hydrogel platform and smartphone-assisted sample-to-answer analyzer for detecting trace pyrethroids

Quantum confinement (QC) effect-related materials have been extensively studied as photoluminescent probes for agricultural, food, and environmental analyses, with the advantage of simple-to-synthesize, reusable, nontoxic, and environmentally friendly. Herein, we propose a strategy to dimerize aromatic cyclo-dipeptides, namely cyclo-ditryptophan (cyclo-WW), cyclo-diphenylalanine (cyclo-FF), and cyclo-dihistidine (cyclo-HH), into quantum dots as basic building blocks for the self-assembly of QC supramolecular structures with excellent photoluminescent properties in aqueous solutions. In particular, through coordination with Zn(II), the bandgap can be tuned to change the photo-absorption and luminescence properties of the cyclo-dipeptide-based QC assemblies. The fluorescence quantum yield of cyclo-WW+Zn(II) was 16.9%. Such a good luminous effect makes it applicable to the detection of LC. A good linear relationship between fluorescence response of cyclo-WW+Zn(II) and LC concentration was observed in the range of 5–350 μg/L, with a low limit of detection of 2.9 μg/L and good spiked recovery of 90.72%–104.3%. A visual platform using the cyclo-WW+Zn(II)-based photoluminescent hydrogel and smartphone-assisted sample-to-answer analyzer were developed, which showed good responsiveness to LC. The developed fluorescence method, validated using traditional HPLC, is a biocompatible alternative for the rapid detection of trace pollutants with the advantages of portability and simple operation.

Self-assembled phenolphthalein functionalized zincite doped silica-anatase nanocomposite as fast responsive optical pH sensor

A pH evaluation is required in numerous fields of life such as environmental monitoring, agriculture, and food science research. The chemical properties (acidity and basicity) of aqueous solutions can be determined by their pH values. Therefore, zincite-supported silica-anatase nanocomposite (ZSAC) is synthesized by the sol-gel method. Owing to the broad pH range 1–12 and fast response pH sensing characteristics, phenolphthalein is immobilized in ZSAC. FESEM analysis exhibited that both nanocomposites exhibited porous and self-assembled structures. Thermally stable ZSAC demonstrates low Ra (surface roughness) 1 nm, refractive index (n) 1.48 at 633 nm, and surface area 282 m2/g which varied to Ra 4 nm, n around 1.5, and surface area 345 m2/g after php immobilization. Both nanocomposites show heterogeneous chemical bonding. PZSAC revealed high pka around 11, fast color response 0.68 s in pH 12, and non-leachable behavior. Experimental findings suggested that synthesized nanocomposite has the capability for opto-chemical sensing applications.

Cationic Imidazolium Amphiphiles Bearing a Methoxyphenyl Fragment: Synthesis, Self-Assembly Behavior, and Antimicrobial Activity.

Novel cationic amphiphiles of the 3-alkyl-1-(4-methoxyphenyl)-1H-imidazol-3-ium bromide series bearing methoxyphenyl fragments (MPI-n) have been synthesized. Their aggregation properties in aqueous solutions, solubilization capacity, and hemolytic and antimicrobial activities have been investigated by a number of physicochemical methods. Using tensiometry, conductometry, and fluorescence spectroscopy, it was shown that the MPI-n have lower CMCs than their nonfunctionalized counterparts. The unusual alkyl-chain-length-dependent morphology of aggregates is testified for this homological series. Amphiphiles with 12, 14, and 16 alkyl tails are characterized by the formation of micellar aggregates, while a surfactant with a decyl tail is characterized by the formation of larger aggregates with lower surface curvature. The MPI-10 aggregate morphology was rationalized in terms of the packing parameter consideration and was supported by size measurements and the fluorescence probe techniques, which showed that vesicle-like aggregates in close-packing mode probably occur. MPI-n aggregates have exhibited a high solubilization capacity toward hydrophobic azo dye Orange OT. Importantly, amphiphiles studied showed (i) high bacteriostatic activity at the level of ciprofloxacin; (ii) high bactericidal action against all Gram-positive bacteria, including methicillin-resistant strains; (iii) bactericidal properties against Gram-negative bacteria; and (iv) low hemolytic activity.

Atomistic Modeling of the Structural and Dynamic Properties of Aqueous NaCl and Na2SO4 Solutions in the Interlayer Space of Ettringite

Atomistic Modeling of the Structural and Dynamic Properties of Aqueous NaCl and Na2SO4 Solutions in the Interlayer Space of Ettringite

A cytostatic drug from the class of triazine derivatives: Its properties in aqueous solutions, cytotoxicity, and therapeutic activity

We present a comprehensive study of a water-soluble substance from the class of triazine derivatives alkylating agents. The performed physicochemical investigations of this cytostatic drug’s aqueous solutions include the measurements of density, viscosity, speed of sound, refraction index, stability, solubility, distribution between water and octan-1-ol, as well as electronic structure calculations and molecular dynamics modelling. Biologically, the substance was investigated for its cytotoxicity as well as in vitro (on Capan-2 and SK-MEL-1 cell lines) and in vivo (transplantable Ehrlich ascites carcinoma model) therapeutic activity.

Influence of ice formation on the dynamic and thermodynamic properties of aqueous solutions

Water dynamics in solutions with biological or non-biological solutes has been intensely studied when both components (solvent and solute) are amorphous. Here, we apply broadband dielectric spectroscopy combined with calorimetric measurements to analyze the dynamics of the aqueous solutions tri-propylene glycol (3PG) and ε-poly (lysine) (ε-PLL), after their water becomes semi-crystalline. Various crystallization levels were explored by conducting experiments with different annealing times at temperatures above the glass transition temperature (Tg). We find that the amount of ice depends on both the time and temperature of the annealing, and that this, in turn, affects Tg and dynamics of the amorphous part of the samples. However, it should be noted that the observed differences are relatively small for the degrees of crystallinity we have studied (up to about 26 wt% of the water). This also implies that the dynamic crossover of the water relaxation from a high temperature non-Arrhenius behavior to a low temperature Arrhenius dependence is unaffected by the partial crystallization and still occurs as a single crossover at the calorimetric Tg. Thus, we cannot detect two different crossovers, as commonly observed for other types of two-component systems, such as two glass formers.

Predicting the Physicochemical Properties and Biological Activities of Monolayer-Protected Gold Nanoparticles Using Simulation-Derived Descriptors.

Gold nanoparticles are versatile materials for biological applications because their properties can be modulated by assembling ligands on their surface to form monolayers. However, the physicochemical properties and behaviors of monolayer-protected nanoparticles in biological environments are difficult to anticipate because they emerge from the interplay of ligand-ligand and ligand-solvent interactions that cannot be readily inferred from ligand chemical structure alone. In this work, we demonstrate that quantitative nanostructure-activity relationship (QNAR) models can employ descriptors calculated from molecular dynamics simulations to predict nanoparticle properties and cellular uptake. We performed atomistic molecular dynamics simulations of 154 monolayer-protected gold nanoparticles and calculated a small library of simulation-derived descriptors that capture nanoparticle structural and chemical properties in aqueous solution. We then parametrized QNAR models using interpretable regression algorithms to predict experimental measurements of nanoparticle octanol-water partition coefficients, zeta potentials, and cellular uptake obtained from a curated database. These models reveal that simulation-derived descriptors can accurately predict experimental trends and provide physical insight into what descriptors are most important for obtaining desired nanoparticle properties or behaviors in biological environments. Finally, we demonstrate model generalizability by predicting cell uptake trends for 12 nanoparticles not included in the original data set. These results demonstrate that QNAR models parametrized with simulation-derived descriptors are accurate, generalizable computational tools that could be used to guide the design of monolayer-protected gold nanoparticles for biological applications without laborious trial-and-error experimentation.

Investigation of the fabrication of nanofibers from aqueous polyvinyl alcohol solutions by electrospinning

Polyvinyl alcohol (PVA) refers to polymers that have great potential for medical and technical applications. Especially, the possibility of its medical application in nanofibres is of great interest due to its good water solubility, high biocompatibility and non-toxicity. PVA is used for various pharmaceutical and biomedical purposes, as a carrier for the delivery of proteins and drugs, as dressings, filter materials, and as artificial organs. Currently, many drug delivery systems have been developed, such as hydrogels or complex electronic microchips. Nanostructural materials are particularly advantageous for rapid drug release due to their high surface area to volume ratio. Both natural and synthetic polymers can be used to produce nanofiber materials, but the combination of different polymers (synthetic and natural) and the incorporation of various biologically active substances into them provides special properties to the finished materials. In this work, the properties of aqueous solutions based on polyvinyl alcohol were investigated: electrical conductivity, viscosity and pH. The influence of technological parameters of electroforming process on obtaining nanofibers from aqueous solutions of PVA. The optimum PVA concentration for the formation of nanostructures was determined equal to 8 wt.%. At this concentration, the PVA solution has electrical conductivity, viscosity and pH equal to 571 µS/cm, 107.23 mPa·s and 6.14 respectively. As part of the study, the electroforming process parameters were obtained to enable the production of nanofibers with a diameter of about 170 nm: distance between needle and collector 140 mm, spinning solution feed rate 0.2 ml/h and voltage between needle and collector 30 kV.

Modeling of Transport Properties of Aqueous Sucrose Solutions by the Molecular Dynamics Method

Modeling of Transport Properties of Aqueous Sucrose Solutions by the Molecular Dynamics Method

Synthesis, crystal structure and biological evaluation of thyroid cancer targeting photosensitizer for photodynamic therapy

With the increasing of thyroid cancer worldwide, there urgently demands new mild theranostic strategies for treatment of recurrence of thyroid cancer to overcome the side-effects of the clinical practices (131I). In this work, photodynamic therapy (PDT) was first explored for treatment of thyroid cancer by incorporating iodomethane choline onto the phthalocyanine through either axial or peripheral substitution. Due to the extraordinary nonaggregation properties in aqueous solution, the axial choline substituted SiPc 1 shows much higher singlet oxygen generation and fluorescence emission than ZnPc 2 and 3 with peripheral substituted cholines. Their photodynamic activities in different type of thyroid cancer cells were clearly compared, disclosing that SiPc 1 is the most promising candidate for PDT of thyroid cancer.