Stoichiometric Polyelectrolyte Complexes Research Articles

Structure and properties of polyelectrolyte complexes of various type (chitosan chloride – polyacrilic acid) and triple polyelectrolyte-metalic complexe with cations Cu2+

Using FT-IR-spectroscopy, X-ray diffraction and thermomechanical analysis structure and thermomechanical properties of two nonstoichiometry and one stoichiometry polyelectrolyte complexes (PEC) based on opposite charged polyelectrolytes – strong cationic polyelectrolyte (chitosan chloride) and weak anionic polyelectrolyte (polyacrylic aсid) and triple polyelectrolyte-metal complexes (TPMC) based on stoichometry polyelectrolyte complexes and cations Cu(II) were investigated. It was shown, that chitosan chloride has amorphous-cristallinity structure, which is significantly different from the structure of neat chitosan, and polyacrylic acid posses amorphous structure. Meantime, all PEC samples have amorphous structure, differing from the structure of weak anionic polyelectrolyte, at the same time amorphous structure of nonstoichiometric PECs insignificantly different from that of stoichiometric polyelectrolyte complexes. Additionally, amorphous structure of TPMC has another structure, compared to all PEC. According to thermomechanical analysis, all PECs have one temperature transition from glassy to highly elastic state (from 77 to 84 °C). The deformation value of the samples of nonstoichiometric PEC is similar and somewhat less than the deformation of the stoichiometric PEC. The TPMC sample has two glass transitions (81 and 226 °C), and his high-temperature transition characterizes the segmental mobility of fragments of macromolecules of one stoichiometric PEC, the polar groups of which form chelate circles with Cu (II) cations. Deformation parameter of the TPMC is higher in comparison with the stoichiometric polyelectrolyte complexes. Keywords: structure, properties, deformation, ionic force, cationic Cu(II), polyelectrolyte, polyelectrolyte-metal complexes, chitosan chloride, polyacrylic acid, X-ray diffraction, thermomechanical analysis.

Analysis of Partitioning of Salt through Doping of Polyelectrolyte Complex Coacervates

Doping of salt ions within stoichiometric polyelectrolyte complex coacervates (PECs) is modeled with a theory that includes polymer ion pairing and counterion adsorption as equilibrium reactions al...

Ion Environments in Mn(2+)-Doped Polyelectrolyte Complexes: Dilute Magnetic Saloplastics.

Amorphous hydrated complexes of the polyelectrolytes poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium) were doped with the spin-5/2 ion Mn(2+). X-band electron paramagnetic resonance (EPR) measurements of the Mn(2+) spins within these stoichiometric polyelectrolyte complexes (PECs) revealed an octahedral coordination environment, similar to that observed in aqueous solutions of Mn(2+). This octahedral symmetry of the [Mn(H2O)6](2+) complexes, observed in fully hydrated PECs, is somewhat distorted because of the wide range of ion pairs possible with the sulfonate group on PSS. As the Mn(2+) concentration was increased, the linewidths broadened, indicating the dominance of dipolar broadening over exchange narrowing in determining the linewidths; that is, any exchange narrowing was masked by the large dipolar broadening. The calculated linewidths were used to estimate the strengths of the dipolar interactions, and hence the distances between the Mn(2+) spins, on the basis of a simple model of regularly spaced spins. The distances calculated by this method were roughly comparable to the geometric average distances calculated on the basis of the Mn(2+) concentrations and densities of the doped PEC samples. From a comparison of their EPR spectra, the ion environments in the doped, fully hydrated PECs were found to be similar to those in hydrated classical ion exchange resins. EPR spectra before and after drying of the PECs indicate the replacement of octahedrally coordinated water by oxide anions from the polyanion chain and the corresponding loss of the symmetric environment of Mn(2+) ions.

The chitosan–gelatin (bio)polyelectrolyte complexes formation in an acidic medium

The interaction of cationic polysaccharide chitosan and gelatin accompanied by the stoichiometric (bio)polyelectrolyte complexes formation has been studied by the methods of capillary viscometry, UV and FTIR spectroscopy and dispersion of light scattering. Complexes were formed in the aqueous phase, with pH being less than the isoelectric point of gelatin (pIgel). The particle size of the disperse phase increases along with the growth of the relative viscosity in comparison with sols of the individual components—polysaccharide and gelatin. Possible models and mechanism of (bio)polyelectrolyte complexes formation have been discussed. It was shown that the complex formation takes place not only due to the hydrogen bonds, but also due to the electrostatic interactions between the positively charged amino-groups of chitosan and negatively charged amino acid residues (glutamic Glu and aspartic Asp acids) of gelatin.

DC field effect on the structuring and thermomechanical and electric properties of nanocomposites formed from pectin—Cu2+—polyethyleneimine ternary polyelectrolyte—metal complexes

With the use of combined structural methods, thermomechanical analysis, and dielectric spectroscopy, the effect of a dc field on the structuring and properties of ternary polyelectrolyte—metal complexes prepared from a stoichiometric polyelectrolyte complex based on the weak polyelectrolytes pectin and polyethyleneimine and CuSO4 salt, as well as nanocomposites formed from these complexes, has been studied. It has been found that the chemical reduction of Cu2+ cations in the bulk of a ternary complex under the action of a dc field occurs via the formation of a nanocomposite consisting of a polyelectrolyte complex and nanoparticles of only the metal Cu phase, whereas nanocomposite with Cu/Cu2O nanoparticles is formed in the absence of field. With the use of thermomechanical analysis and dielectric spectroscopy, it has been shown that, under a dc field, nanocomposites with higher structural glass-transition temperatures and electric conductivities are formed.

Structuring, morphology, and thermomechanical properties of nanocomposites formed from ternary polyelectrolyte-metal complexes based on pectin, polyethyleneimine, and CuSO4

The structures and properties of ternary polyelectrolyte-metal complexes obtained from a stoichiometric polyelectrolyte complex based on the weak polyelectrolytes pectin and polyethyleneimine and the salt CuSO4 and from nanocomposites formed on their basis have been studied with the use of a range of structural techniques and thermomechanical analysis. Nanocomposites based on the stoichiometric polyelectrolyte complex and Cu/Cu2O nanoparticles are formed as a result of the chemical reduction of Cu2+ cations by NaBH4 in the ternary metal-polyelectrolyte complexes, and the full structural appearance of the metal Cu phase is observed at a BH4−-to-Cu2+ molar ratio of 6. The chemical reduction of Cu2+ cations is shown to occur with the formation of the nanocomposite with nanoparticles of only the metallic Cu phase in ternary polyelectrolyte-metal complexes subjected to a constant magnetic field.

The Polyelectrolyte Complex/Coacervate Continuum

Stoichiometric polyelectrolyte complexes (PECs) of the strong polyelectrolytes poly(styrenesulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) were dissociated and dissolved in aqueous KBr. Water was added to dilute the salt, allowing polyelectrolytes to reassociate. After appropriate equilibration, these mixtures yielded compositions spanning complexes (solid) to coacervates (elastic liquid) to dissolved solutions with increasing [KBr]. These compositions were defined by a ternary polymer/water/salt phase diagram. For coacervates, transient microphase separation could be induced by a small departure from equilibration temperature. A boundary between complex and coacervate states was defined by the crossover point between loss and storage modulus. Salt ions within the complex/coacervate were identified as either ion paired with polyelectrolytes (“doping”) or unassociated. The fraction of ion pair cross-links between polyelectrolytes as a function of KBr concentration was used to account for viscosity using a model of “sticky” reptation.

The Possibility of Obtaining Films by Single Sedimentation of Polyelectrolyte Complexes

Surface coatings obtained by a step-by-step (SBS) deposition process of polymers carrying mutually complementary moieties (like polycations and polyanions) allow for a versatile multifunctionalization of a vast kind of materials. However the SBS deposition process can be extremely time-consuming when it is performed by alternatively dipping the substrates in the solutions carrying the interacting species. There is hence an important need to obtain coatings of similar composition as those obtained in the SBS manner but in a “one pot” manner. Here we show that the sedimentation of stoichiometric polyelectrolyte complexes can lead to a homogeneous coating. This is possible if the polylectrolyte complexes display a high internal mobility. The film growth rate is then in direct relation with the sedimentation rate of its constituting complexes. On the other hand when the interactions between the oppositely charged polyelectrolytes are too strong, the obtained coating is neither continuous nor homogeneous.

Polymer colloids formed by polyelectrolyte complexation of vinyl polymers and polysaccharides in aqueous solution

The polyelectrolyte complex formed from the polyanion and polycation was studied by turbidimetry, static and electrophoretic light scattering, and elementary analysis. Sodium salts of polyacrylate (PA) and heparin (Hep) were chosen as the polyanion, and hydrochloric salts of poly(vinyl amine) (PVA) and chitosan (Chts) as the polycation. Although these vinyl polymers and polysaccharides have remarkably different backbone chemical structures and linear charge densities, all the four combinations PA-PVA, PA-Chts, Hep-PVA, and Hep-Chts provide almost stoichiometric polyelectrolyte complexes which are slightly charged owing to the adsorption of the excess polyelectrolyte component onto the neutral complex. The charges stabilize the complex colloids in aqueous solution of a non-stoichiometric mixture, and the aggregation number of the complex colloids increases with approaching to the stoichiometric mixing ratio. The mixing ratio dependence of the aggregation number for the four complexes is explained by the model proposed in the previous study.

A Small-Angle Neutron Scattering Study of the Equilibrium Conformation of Polyelectrolytes in Stoichiometric Saloplastic Polyelectrolyte Complexes

Stoichiometric polyelectrolyte complexes, PECs, from fully sulfonated poly(styrenesulfonate), PSS, as polyanion and poly(diallyldimethylammonium chloride), PDADMA, as polycation, were prepared by mixing them at optimized polyelectrolyte and NaCl concentrations. The complexes were compacted by ultracentrifugtion and then annealed in NaCl solutions at elevated temperatures to allow the polymers to fully intermix and relax. Small-angle neutron scattering, SANS, with contrast matching, was used to study single polyelectrolyte chain dimensions in PECs made from a mixture of deuterated and protonated PSS chains. Two PSS molecular weights in PECs were investigated at various ionic strengths. SANS curves, form factor fits, and corresponding Kratky plots indicate the Gaussian nature of the polyelectrolyte chains in the complexes regardless of molecular weight. PSS coils were slightly larger than the unperturbed dimension, more so for the higher molecular weight material, which was attributed to an effective stiffening of the chain due to ladderlike interactions between polyelectrolytes.

Phase state of polyelectrolyte complexes based on blends of acrylic copolymers

AbstractThe phase state of polyelectrolyte blends based on acrylic copolymers was investigated with differential scanning calorimetry, transmission electron microscopy (TEM), and wedge microinterferometry as a function of the blend composition and ionization of polymer functional groups. A copolymer of N,N‐dimethylaminoethyl methacrylate with methyl methacrylate and butyl methacrylate was used as a polybase, a copolymer of methacrylic acid and ethyl acrylate was employed as a polyacid, and the optional plasticizer was triethyl citrate. A correlation was established between an earlier described mechanism of molecular interaction and the behavior of the glass‐transition temperature (Tg) of the polymer blends. The Tg values of the polyelectrolyte complexes in the gel phase were always higher than Tg in the sol phase. This fact implies that intermolecular cohesion dominated the free volume in the stoichiometric polyelectrolyte complexes formed in the gel phase, whereas nonstoichiometric complexes formed in the sol phase were characterized with the predominant contribution of free volume. TEM and interferograms of polyelectrolyte blends showed the signs of anisotropic ordered supramolecular structure formation. A phase‐state diagram of the polyelectrolyte blends was constructed. The stoichiometric polyelectrolyte complex was immiscible with parent polymers, forming a separate phase that became melted at elevation of temperature because of complex dissociation. Polyelectrolyte miscibility was supposed to result rather from the chemical reaction of the complex formation than from interdiffusion of the polymer components along the gradient of their concentration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Conductometric and Light Scattering Studies on the Complexation between Cationic Polyelectrolyte Nanogel and Anionic Polyion

This work aims to provide a basic understanding of the water dispersibility of a 1:1 stoichiometric polyelectrolyte complex (SPEC) in water in the absence of low-molecular-weight salts. We studied the complexation of a linear polyanion, potassium poly(vinyl alcohol sulfate) (KPVS), with a cationic polyelectrolyte nanogel (CPENG) composed of a lightly cross-linked copolymer of N-isopropylacrylamide and 1-vinylimidazole, in an aqueous salt-free solution (pH 3 and 25 °C), as a function of the molar mixing ratio (Mmr) of anionic to cationic groups. Also studied for comparison was the complexation of KPVS with poly(diallyldimethylammonium chloride) (PDDA), which is a standard reaction in colloid titration. Turbidimetric and conductometric measurements were used in combination of dynamic light scattering (DLS). An abrupt increase of turbidity curve and a break of conductivity curve were observed at Mmr =1 when KPVS was added to the CPENG or PDDA solution, indicating the formation of SPEC. All the complexes formed at Mmr ≤ 1 were water-dispersible and hence characterized by DLS. The CONTIN analysis of DLS data showed that (i) an increase of Mmr causes a decrease of the hydrodynamic radius (R(h)) of the nanogel complex particle but (ii) the R(h) of the PDDA complex remains unchanged at Mmr < 0.8. Taking these into account, we discussed the conductometric results in terms of the random model (RM) and all-or-none model (AONM) in polyelectrolyte complex formations. It was found that KPVS and PDDA yield a water-dispersible SPEC particle at each Mmr, accompanying the uptake of counterions (K(+) and Cl(-)) by the complex. This uptake amount was about 7% of the stoichiometric release of the counterions. In the nanogel system, a complete release of the counterions was observed at Mmr < 0.2 at which one or two KPVS chains were bound to a CPENG particle, but further KPVS binding led to about 20% of the counterion uptake to maintain electroneutrality. Thus, we suggest that the counterion uptake becomes a key factor to understand the water dispersibility of SPEC particles.

The effect of a low-molecular-mass salt on stoichiometric polyelectrolyte complexes composed of oppositely charged macromolecules with different solvent affinities

The effect of a low-molecular-mass salt on the thermodynamic stability of stoichiometric interpolymer complexes composed of oppositely charged macromolecules with different solvent affinities has been theoretically studied. It has been shown that the dissociation of such complexes with an increase in the concentration of the salt proceeds via several stages. At a low concentration of the salt, complexes retain their structure and dimensions. When a certain critical concentration of the salt nscr is achieved, the dimensions of the complex increase abruptly. At this concentration, macromolecules involved in the complex begin to separate, and at concentration ns*, they fully move apart but remain soluble owing to the polyelectrolyte effect. Upon a further increase in the concentration of the salt, the polyelectrolyte effect is shielded and the dimensions of macromolecules decrease. The critical concentration of the low-molecular-mass salt, nscr, increases with an increase in the degree of ionization of macromolecules and a decrease in the affinity of the hydrophilic component for water and diminishes with the degree of polymerization of macromolecules and the degree of hydrophobicity of a polycation. Because of the easy formation of soluble complexes from oppositely charged macromolecules differing in solvent affinities and their high stability in solutions of a low-molecularmass salt, such complexes are promising for wide use in medicine and pharmaceutical practice.

Stoichiometric and nonstoichiometric polyelectrolyte complex of chitosan and polyethyleneglycol-monosuccinate: Preparation and characterization

Stoichiometric and nonstoichiometric polyelectrolyte complex (PEC) was prepared with polyethylene glycol-monosuccinate (PEGMS), and chitosan (CS). A series of PEGMS were synthesized by a 1 : 1 mol ratio between PEG and succinic anhydride. Then, the novel PEC was prepared by a various mole reaction of the above synthesized PEGMS and CS. The physicochemical properties of the synthesized PEC was characterized by using elemental analysis, FTIR, 1H, and 13C nuclear magnetic resonance, dissolution behavior, and phase transition phenomenon. Furthermore, some properties of the PEC obtained were analyzed by UV-Visible spectrometry, wide-angle X-ray diffraction, differential scanning calorimeter, scanning electron microscope, and estimated solubility, and cell viability assay, respectively. It was found that the observed FTIR, 1H, and 13C-NMR data was in good agreement with the chemical structure of the prepared PEGMS and PEC. The dissolution behaviors of nonstoichiometric PEC were found to depend on the pH of the solution as well as on the PEGMS/CS composition. The study of MTT assay suggested that the viability of HepG2 human hepatoblastoma cell on PEC were increased significantly in accordance with mole ratio of CS. As the results, the obtained several product is a useful intermediate, which permits further chemical modification for the amino group of CS and may have potential applications in biocompatible or cosmetic systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Stoichiometric polyelectrolyte complexes of ionic block copolymers and oppositely charged polyions

Micellization in dilute solutions of diblock copolymers with a polyelectrolyte and a hydrophilic nonionic blocks and oppositely charged polyions is studied using mean-field theory. In aqueous solutions the micelle core consists of the polyelectrolyte complex (PEC) while the corona is formed by hydrophilic blocks of the block copolymers. Describing PEC as a globule in the framework of the Lifshitz [Zh. Eksp. Teor. Fiz. 55, 2408 (1968)] globule theory we calculate the surface tension of the micellar core/solvent interface as a function of the polyion degree of ionization, solvent quality, and concentration of low-molecular-mass salt. The equilibrium aggregation number of starlike micelles formed by block copolymers and homopolymers of opposite charge at stoichiometric mixture compositions is found as a function of the system parameters. It is shown that micelles disintegrate upon addition of salt.

Stoichiometric polyelectrolyte complexes as comb copolymers

The collapse behavior of a single comblike copolymer chain has been studied by Monte Carlo simulations. It has been supposed that the solvent is good for the side chains but the solvent quality for the backbone chain changes. It has been shown that depending on the structural parameters of the comb copolymer (the lengths of the backbone and side chains, grafting density of the side chains) various thermodynamically stable morphologies of the collapsed backbone chain can be realized. In addition to ordinary spherical globule we have observed elongated structures as well as necklace-like conformations. The proposed model can be used to describe conformational behavior of stoichiometric complexes between block copolymers with a polyelectrolyte short block and oppositely charged linear homopolymers.

Polyelectrolyte Complexes of Homo- and Copolymers of Vinyl Ether of Monoethanolamine with Poly(Acrylic Acid) in Aqueous Solutions

The complexation of homo- and copolymers of vinyl ether of monoethanolamine with poly(acrylic acid) has been studied in aqueous solutions. The effect of pH on the complexation has been shown. In acidic media (pH 2.4), the polyelectrolyte complex is enriched by anionic polymer units. In weakly acidic media (pH 4–6), the formation of stoichiometric polyelectrolyte complex is observed. In higher pH media (pH 6–8), the polycomplex contains an excessive amount of cationic polymer. The stability of the polyelectrolyte complexes is affected by the addition of inorganic salts and dimethylformamide.

Smart Polymers and Protein Purification

Smart polymers undergo fast and reversible changes in microstructure triggered by small changes of medium property (pH, temperature, ionic strength). These properties of smart polymers were exploited for the development of new protein purification techniques: affinity precipitation, affinity partitioning, and temperature-induced elution in dye-affinity chromatography. Different smart polymers were used for affinity precipitation: Eudragit S 100 (a copolymer of methacrylic acid and methyl methacrylate which precipitates on decreasing pH); stoichiomet-ric polyelectrolyte complexes of poly(methacrylate) and poly(N-ethyl-4-vinylpyridium bromide); poly(N-vinyl caprolactam), and poly(N-iso-propylacrylamide) (both precipitate on heating aqueous solutions to 35–40°C or increase in ionic strength). Recombinant thermostable lac-tate dehydrogenase from a thermophile Bacillus stear other mophilus was purified by affinity partitioning in an aqueous two-phase polymer system formed by dextran and a copolymer of N-vinyl caprolactam and 1-vinyl imidazole. The enzyme partitioned preferentially into the copolymer phase in the presence of Cu ions. The thermoprecipitation of the copolymer at 45°C resulted in an aqueous solution of the purified en- At elevated temperatures, poly-VCL molecules are in a compact globule conformation, capable of binding only to a few ligands on the matrix. The enzyme lactate dehydrogenase from porcine muscle has better access to the ligands and binds to the column. With a decrease in temperature, the polymer molecules undergo transition to a more expanded coil conformation. Polymer molecules interact now with more ligands and begin to compete with the bound enzyme for the ligands. Finally, the bound enzyme is replaced by the expanded polymer chains. This system was used for lactate dehydrogenase purification. Porcine muscle homogenate was applied on a column until breakthrough at 40°C. The foreign proteins were washed out with 0.1 M KC1; then the column was cooled to room temperature and virtually homogeneous lactate dehydrogenase was eluted with the same buffer. The purification factor was 17; recovery was 90% (13).

Study of the stoichiometric polyelectrolyte complex between chitosan and carboxymethyl cellulose

The polyelectrolyte complex (PEC) between chitosan and carboxymethyl cellulose was studied. Turbidimetric measurements revealed that the amount of stoichiometric PEC increased gradually as the solution of one polyelectrolyte was added to the other; the turbidity of the solution reached a maximum for the stoichiometric ratio of the reacting polyelectrolytes in the mixture. At pH 4,0 the composition of the complex is very near to equimolarity. IR spectra and thermal analysis of the PEC exhibited significant differences from those of the 1:1 mixture of the starting polyelectrolytes.

Phase separation in water-salt solutions of polyelectrolyte complexes

Phase separation in water-salt solutions of stoichiometric polyelectrolyte complexes, which are the products of the reaction between oppositely charged polyelectrolytes, is studied. It is shown that the compositions and volumes of the coexisting phases are largely determined by the degree of conversion in the inter-polymer reaction, which depends on the concentrations of teh polycomplex and low molecular salt. The effects of the nature of the low molecular salt, the molecular masses of the interacting polyelectrolytes, and the temperature on the phase equilibrium of the polyelectrolyte complex-water-salt system are studied.