Protonated member of poly(diallylammonium) family: Hydrodynamic and conformational properties

Secondary polyamine in protonated salt form – poly(diallylammonium trifluoro-acetate) is characterized as representative of polymer series based on N,N-diallyl-ammonium. Its hydrodynamic behavior in 1 M NaCl has been compared with the other series members – quaternary poly(diallyldimethylammonium chloride) and tertiary poly(diallylmethylammonium trifluoroacetate). It was shown that these polymers belong to semirigid class whose Kuhn segment length ～4?nm just slightly depends on chemical structure at high ionic strength. As specific for secondary polyamine, the sensitivity to proton equilibrium in solution and counter ion type was detected resulting in great difference of its Mark–Kuhn–Houwink equations from the quaternary analogue at the same conditions.     

Microwave dielectric permittivity and relaxation for aqueous potassium trifluoroacetate solutions

The results of microwave dielectric measurements in aqueous potassium trifluoroacetate solutions at seven frequencies (ranging within 7.5–25 GHz) at 288, 298, and 308 K are presented. Static dielectric constants, dielectric relaxation times and activation parameters are calculated. The H-bond network in potassium trifluoroacetate solutions is shown to experience molecular-kinetic stabilization and an increase in connectivity and structuring, which are similar to those experienced by water in potassium acetate solutions. These changes are associated with the hydrophobic hydration of trifluoroacetate ion, which was first determined by microwave dielectric spectroscopy and arises from the effect of the low-polarity CF₃ group of trifluoroacetate ion.     

Effect of dielectric properties and structure of aqueous solutions of diallylammonium salts on their reactivity in radical polymerization

The complex dielectric permittivity in the frequency range 7.5–25.0 GHz and the low-frequency specific conductivity of aqueous solutions of diallylammonium salts (diallylammonium and diallylmethylammonium trifluoroacetates and diallyldimethylammonium chloride) were measured at 293–308 K over a wide concentration range. On the basis of the results, the parameters of dielectric relaxation were calculated. The number of water molecules in the solvation shell of the salts was estimated. The concentration behavior of the initial rate of radical polymerization of diallylammonium salts and the rate constant of bimolecular chain termination was correlated with the specific features of the structure of aqueous monomer solutions. The role of “free” water in the initial salt solutions was revealed, a species whose presence in the system determines the character of concentration behavior of the rate constants for the elementary steps of polymerization, such as propagation, chain transfer to the monomer, and bimolecular chain termination.     

Radical Polymerization of Protonated Diallylammonium Monomers in Bidistilled Aqueous Solution: Kinetic Study

The kinetics of the radical polymerization of protonated monomers of the diallylammonium series (diallyl- and diallylmethylammonium trifluoroacetates) in bidistilled aqueous solution (quartz bidistiller) is studied in situ using ¹Н NMR spectroscopy. The rates of monomer consumption and polymer accumulation in the range of 30–50°С are determined. For diallylammonium trifluoroacetate, the effective activation energy of polymerization and the constant of chain transfer to the monomer (30°С) are estimated. It is found that the initial rates of polymerization are comparable with the rates of polymerization of quaternized analogs and the constant of chain transfer to the monomer and the activation energy of polymerization are close to the analogous characteristics of polymerization in the case of quaternized diallyldimethylammonium chloride. It is shown that for polymerization in bidistilled solution, the constant of chain transfer to the monomer (30°С, 3.8 × 10^–3) is more than three times lower than that for polymerization in monodistillate (30°С, 12.2 × 10^–3) and the ММ of the polymers is ~2.4 times higher than the ММ of the samples synthesized in monodistillate under the same conditions. It is ascertained that standard electrolyte admixtures in distilled aqueous solution considerably affect radical chemical reactions involving protonated forms.     

Interaction between Na+ and polymer in aqueous solution of sodium salts of poly(2-hydroxyethyl methacrylate-co-methacrylic acid) studied by 23Na-NMR

The interaction between Na⁺ and polymer was studied by ²³Na-NMR for the aqueous solution of P(HEMA-co-MAANa), sodium salt of poly(2-hydroxyethyl methacrylate-co-methacrylic acid), as a function of the polymer concentration, charge density of the polymer chain, and temperature. The NMR line width of ²³Na-NMR in 1% (w/v) aqueous solution of the P(HEMA-co-MAANa) narrowed with increasing temperature due to the rapid exchange of Na⁺ between free and polymer-bound states with a rate of exchange exceeding the quadrupolar relaxation rate in the latter state. At high concentrations of the polymer above 1.0% (w/v) at 298 K, the ²³Na-NMR relaxation fits for a single Lorentzian due to the rapid exchange between two Na⁺ states. However, it follows a biexponential decay of magnetization in dilute solutions of polymer. The biexponential decay character of relaxation increased with the increase of the fraction of the MAANa monomer unit on the polymer chain. This feature of ²³Na-NMR relaxation was used to deduce the correlation time (τ_c), the degree of binding (p_B), and the quadrupole coupling constants (X) of the polymer-bound counterion. The χ and τ_c values show that the mobilities of the polymer chain are correlated with the motion of Na⁺ in aqueous solution of the polymer and there is a small degree of the specific binding between COO^? and Na⁺. No evidence in support of the intramolecular conformational change by the charge density variation in P(HEMA-co-MAANa) was obtained. © 1993 John Wiley & Sons, Inc.     

Nonlinear depression of the lower critical solution temperatures in aqueous solutions of thermo-sensitive random copolymers

We develop a theoretical model of cooperative hydration to clarify the molecular origin of the observed nonlinear depression of the lower critical solution temperature (LCST) in the aqueous solutions of thermosensitive random copolymers and find the monomer composition at which LCST shows a minimum. Phase diagrams of poly(N-isopropylacrylamide-co-N,N-diethylacrylamide) copolymer solutions are theoretically derived on the basis of the theory of cooperative hydration by introducing the microscopic structure parameter η which characterizes the distribution of the monomer sequences along the chains. We compared them with the experimental data of LCST of random copolymers with various monomer compositions and also of the diblock copolymers with equimolar monomer composition. The transition temperature shifts to lower than those of homopolymer counterparts when the monomer sequence of the chains has an alternative tendency. On the contrary, for the blocky polymers such as diblock copolymers, the transition temperature remains almost the same as those of the homopolymers. Thus, the nonlinear effect in phase separation appears when the average block length of the copolymers is shorter than the average sequence length of the cooperative hydration. The degree of hydration is calculated as a function of the temperature and polymer concentration for varied distribution of the copolymer compositions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1112–1123     

Hydrogen-bonding dynamics in aqueous solutions of amides and acids: monomer, dimer, trimer, and polymer

Hydrogen-bonding dynamics in aqueous solutions of series of amides and acids have been investigated by means of femtosecond Raman-induced Kerr effect spectroscopy and ab initio quantum chemistry calculation. The amides and acids studied here are acetamide, 1,3-propanedicarboxamide, 1,3,5-pentanetricaroxamide, polyacrylamide with Mw=1500, acetic acid, 1,3-propanedicarboxylic acid, 1,3,5-pentanetricarboxylic acid, and poly(acrylic acid) with Mw=2000. The femtosecond damped transient feature for aqueous amide solutions, which arises from the intermolecular hydrogen bonds of amide and water, becomes clearer with the larger molecular weight of amide. A characteristic vibrational band at about 100 cm(-1) is assigned as the hydrogen-bonding vibrational mode and the ab initio quantum chemistry calculation result indicates that at least two waters, which make up the hydrogen-bonding network with amide, are necessary for this mode. The hydrogen-bonding vibrational mode at about 100 cm(-1) in aqueous amide solutions shifts to the higher frequency with the larger molecular weight amide in consequence of the stronger intermolecular interaction between amide and water. The evidence likely comes from the stronger hydrophobic interaction for polymer than oligomers and monomer. In the picosecond time region, an extra slow relaxation process with a time constant of about 60 ps has been found in the aqueous polymer solutions. The relaxation is assigned as a local motion of the constitutional repeat unit of polymers from comparison with monomer and oligomers.     

Solute�CSolvent Interactions in Aqueous Glycylglycine�CCuCl2 Solutions: Acoustical and Molecular Dynamics Perspective

Acoustical and molecular dynamics studies were carried out to understand the various interactions present in glycylglycine?CCuCl₂ aqueous solutions. Amongst these interactions, hydrogen bonding and solute?Csolvent interactions have been highlighted in this study. The radial distribution function (RDF) was used to investigate solution structure and hydration parameters. Binding of Cu²⁺ with various polar peptide atoms reveals the nature and degree of binding. The formation of complex clusters between glycylglycine and water molecules increases the relaxation time. The first hydration shell considerably influences the structure of the second shell, facilitating the formation of an ordered hydrogen bonded network. Both experimental and theoretical results have proved to be efficient in analyzing the behavior of molecules and to give a clear idea on molecular interactions in solutions.     

Synthesis and properties of temperature-resistant and salt-tolerant tetra-acrylamide copolymer

Abstract

The acrylamide copolymer with acrylamide as its main monomer is a modified polyacrylamide. In addition, the acrylamide copolymer is generally to dissolve or swell in water and can be used as thickener, dispersant, flocculant and so on. Therefore, using Acrylamide AM, 2-acrylamide-2-methyl propanesulfonic acid AMPS, dimethyldodecyl (2-acrylamidoethyl) ammoniumbromide AQ₁₂ and vinyltriethoxysilane VTEO as raw materials so that a series of four-membered acrylamide copolymers are prepared in aqueous solution polymerization. The amphoteric structure in the polymer has a unique anti-polyelectrolyte behavior when it is electrically neutral, which can significantly improve the salt resistance of the aqueous polymer. In addition, the hydrolysis of the vinyltriethoxysilane containing silicon structure by hydrophobic association can improve the temperature resistance of the polymer. The optimal reaction conditions were determined by orthogonal experiment: the reaction temperature was 10?°C; the initiator concentration was 0.05?mol%; the monomer concentration was 25?wt% and the pH was 7. Properties of polymer solution indicated that the series of tetra-copolymer possessed salt-tolerant and heat-resisting performances. As an oil displacing agent, it can significantly improve the efficiency of oil displacement, and particularly highlights the effect of 4-member copolymer as an oil displacing agent.     

Solute-solvent contact by intermolecular cross relaxation. I. The nature of the water-hydrophobic interface

Intermolecular cross-relaxation rates between solute and solvent were measured by {1H} 19F nuclear magnetic resonance experiments in aqueous molecular solutions of ammonium perfluoro-octanoate and sodium trifluoroacetate. The experiments performed at three different magnetic fields provide frequency-dependent cross-relaxation rates which demonstrate clearly the lack of extreme narrowing for nuclear spin relaxation by diffusionally modulated intermolecular interactions. Supplemented by suitable intramolecular cross-relaxation, longitudinal relaxation, and self-diffusion data, the obtained cross-relaxation rates are evaluated within the framework of recent relaxation models and provide information about the hydrophobic hydration. In particular, water dynamics around the trifluoromethyl group in ammonium perfluoro-octanoate are more retarded than that in the smaller trifluoroacetate.     

Hydration and dielectrical properties of aqueous pyrrolidinium trifluoroacetate solutions

Results from microwave measurements of the dielectrical properties of aqueous pyrrolidinium trifluoroacetate solutions at maximum water dispersion frequencies (13–25 GHz) and temperatures of 288, 298, and 308 K are given. The static dielectrical constants, times, and activation parameters of the dielectrical relaxation of solutions are calculated. The enthalpy and time of dielectrical relaxation activation are increased by deceleration of the motion of water molecules in the hydrate shells of ions. The changes in dielectrical parameters are in this case minimal in a series of aqueous solutions of diallylammonium salts with cations of different structures and degrees of substitution. It is shown that pyrrolidinium ions are characterized by weak hydrophobic hydration.     

Dielectric constant and dielectric relaxation in aqueous solutions of K<Subscript>2</Subscript>[PdCl<Subscript>4</Subscript>] and K<Subscript>2</Subscript>[PtCl<Subscript>4</Subscript>]

The MW-dielectric properties of aqueous solutions of K₂[PtCl₄] (I) and K₂[PdCl₄] (II) were studied at 298 and 313 K in the frequency range (12–25 GHz) corresponding to the maximum dielectric constant dispersion for water and aqueous solutions of these salts. The low-frequency conductivities were measured. The static dielectric constant, the dielectric relaxation time, and the enthalpy of activation of the dielectric relaxation of the solutions were determined. Compared to pure water, in solutions of salts I and II, the orientational mobility of water molecules is increased and the network of H-bonds is violated more strongly than that of most other ions with hydrophilic hydration. It was demonstrated for the first time that dielectric spectroscopy can be used for analyzing complexation processes in systems containing aqua and hydroxo chloride complexes of metals.     

Measurement of rotational diffusivity of rodlike molecules in amorphous polymer matrices by the dynamic kerr effect

Electrooptic (Kerr effect) relaxation experiments, designed to measure the rotational diffusivity of collagen (rodlike) molecules in aqueous poly(ethyleneoxide) (amorphous) semidilute solutions under various conditions have been performed. The experimental results have been compared with the predictions of a previously derived model giving the rotational diffusivity of dilute rods in semidilute amorphous polymer solutions as a function of rod length and amorphous polymer concentration. Excellent agreement is found between the predicted scaling D_r ～ ?L^?7 (D_r = rod rotational diffusivity, pi_p = polymer weight fraction, and L = rod length) and the experiments.     

Hydration of the hydrogen ion in aqueous solutions from intensity of the OD band of HDO

The OD band of HDO has been studied in partly deuterated aqueous solutions of acids: hydrochloric, sulfuric, nitric, trifluoroacetic, and perchloric. Composition of the hydrogen ion is determined. Observations are made on hydration of the perchlorate and trifluoroacetate ions.     

Studies of micro-brownian motion of a polymer chain by the fluorescence polarization method. II. Segmental motions in concentrated polymer solutions

The fluorescence polarization method has been used to study the micro-Brownian motion of a terminal segement of a polymer chain in concentrated solutions. A new apparatus for determining the fluorescence intensity and its polarization degree was designed. By using this apparatus, the rotational relaxation time 〈ρ〉 of the terminal segment of the fluorescent conjugates of polyacrylamide in aqueous polyacrylamide solutions was obtained as a function of polymer concentration from 0 to 65%, molecular weight of the conjugate from 3.5 × 10⁴ to 3 × 10⁵, and temperature from 10 to 30°C. The logarithm of 〈ρ〉 increased approximately linearly with increasing polymer concentration. This increase in 〈ρ〉, amounting to a factor of 20 times, was less marked than that in macroscopic viscosity. At concentrations less than 30%, 〈ρ〉 depended appreciably on the molecular weight of the conjugate.     

Temperature changes of dielectric permittivity and relaxation in aqueous lithium iodide solutions

The complex permittivity of aqueous LiI solutions is studied over a wide range of concentrations at temperatures of 288–323 K in the water permittivity dispersion region at seven frequencies in the range of 7.5–25 GHz. One relaxation region describable by the Debye or Cole-Cole equation is observed in these solutions. Dielectric relaxation time τ and static permittivity ?_s are studied as dependent on temperature and concentration. The time and enthalpy of activation of dielectric relaxation decrease in going from water to solutions, which corresponds to the distortion of the initial water structure and the increasing mobility of water molecules in hydration shells of ions. In the initial concentration range, the water activity is a linear function of 1/?_s. The negative temperature dependence of ?_s disappears in going to concentrated solutions. At high concentrations, the static dielectric constant increases in response to increasing temperature. The new trends in ?_s and τ at elevated temperatures of 313–323 K are due to the formation of ion pairs and other ion-water groups having high dipole moments.     

Nuclear magnetic relaxation in aqueous solutions of vinylpyrrolidone and polyvinylpyrrolidone

Deuteron magnetic spin-lattice relaxation times have been measured in D₂O solutions of vinylpyrrolidone and polyvinylpyrrolidone as a function of concentration and temperature. For the monomer the results are interpreted in terms of a hydrophobic hydrations effect in which 42 D₂O molecules per solute molecule have a correlation time of 3.2 psec at 298°K. Application of the transition state theory to the temperature dependence gave H^*=21 kJ mole^–1 for the relaxation process. In the case of the polymer it is argued that a hydrophilic hydration effect dominates the observed relaxation. These activation enthalpy at 298°K is 24 kJ-mole^–1. Assuming a hydration number of one D₂O per polymer unit, the correlation time for the bound water is 77 psec at 298°K. Polymer proton spin-lattice relaxation times were measured as a function of frequency, and the results are analyzed in terms of a log normal distribution of correlation times. The median value at 296°K is 1.2 nsec.     

Hydrostatic pressure effects on polymer cholesteric liquid-crystalline structure. I. Equilibrium structure of hydroxypropyl cellulose aqueous solution

Abstract

The effect of pressure on the polymer cholesteric liquid-crystalline structure of hydroxypropyl cellulose aqueous solutions was studied using reflection spectra measurements. Pressures applied to the polymer liquid crystals ranged from 1 to 2000 bar. The equilibrium reflection spectrum of the cholesteric structure shifted to longer wavelengths, showing that the cholesteric pitch of the liquid-crystalline structure increases as the applied pressure increases. At pressures higher than 200 bar the maximum wavelength of reflection shifted linearly with the increase in applied pressure. At lower pressures, the cholesteric structure was influenced by the surface plane of the quartz window.     

Determination of Soluble Polymer in Acrylamide Monomer Solution by Aqueous GEL Permeation Chromatography

Abstract

An aqueous gel permeation chromatographic method for the determination of soluble polymer in aqueous acrylamide monomer has been developed. Polymer content can be determined in four minutes with consecutive analyses every twenty minutes. The relative precision of the method is better than 2.5% at the 95% confidence level in the range of 100 to 600 ppm polymer. The detection limit for the method is 5 ppm.     

Solution Properties of Poly(ethylene Oxide) as Determined by Viscometric Measurements in Aqueous Salt Solutions

The properties of dilute solutions of poly(ethylene oxide) (PEO) in aqueous salt solutions are studied by measurements of intrinsic viscosity [n] in theta and nontheta solvents. The unperturbed dimensions in various salt solutions were found larger than those in pure water. These results are attributed to a change in the polymer hydration sheath, in the uche-transilibrium in the PEO chain in aqueous solutions, and in the water structure because of the added salt. Also, for carboxylic anions, similar behavior is expected due to the interaction of the ether oxygens of PEO with the weak acids through hydrogen bonding. The enthalpy and entropy dilution parameters XHand XS were observed to take on negative and positive values, respectively.