Alexander B. Zezin

Water-soluble complexes of star-shaped poly(acrylic acid) with quaternized poly(4-vinylpyridine).

The interaction of star-shaped poly(acrylic acid) having various numbers of arms (5, 8, and 21) and a strong cationic polyelectrolyte, viz., poly( N-ethyl-4-vinylpyridinium bromide), was examined at pH 7 by means of turbidimetry and dynamic light scattering. Mixing aqueous solutions of the oppositely charged polymeric components was found to result in phase separation only if their base-molar ratio Z = [N+]/[COO (-) + COOH] exceeds a certain critical value ZM ( ZM < 1); this threshold value is determined by the number of arms of the star-shaped polyelectrolyte and the ionic strength of the surrounding solution. At Z < ZM, the homogeneous aqueous mixtures of the oppositely charged polymeric components contain two types of complex species clearly differing in their sizes, with the fractions of these species appearing to depend distinctly on the number of arms of the star-shaped poly(acrylic acid), the base-molar ratio of the oppositely charged polymeric components in their mixtures, and the ionic strength of the surrounding solution. The small complex species (major fraction) are assumed to represent the particles of the water-soluble interpolyelectrolyte complex whereas the large complex species (minor fraction) are considered to be complex aggregates.

Spontaneous Assembly of Miktoarm Stars into Vesicular Interpolyelectrolyte Complexes

Mixing a bis-hydrophilic, cationic miktoarm star polymer with a linear polyanion leads to the formation of unilamellar polymersomes, which consist of an interpolyelectrolyte complex (IPEC) wall sandwiched between poly(ethylene oxide) brushes. The experimental finding of this rare IPEC morphology is rationalized theoretically: the star architecture forces the assembly into a vesicular shape due to the high entropic penalty for stretching of the insoluble arms in non-planar morphologies. The transmission electron microscopy of vitrified samples (cryogenic TEM) is compared with the samples at ambient conditions (in situ TEM), giving one of the first TEM reports on soft matter in its pristine environment.

Interpolyelectrolyte Complexes Based on Polyionic Species of Branched Topology

This review reports advances in experimental and theoretical research on interpolyelectrolyte complexes based on polyionic species of star-shaped polyelectrolytes, cylindrical polyelectrolyte brushes, and micelles of ionic amphiphilic block co- and terpolymers.

Preparation and properties of penicillin amidase immobilized in polyelectrolyte complexes

Abstract (1) Immobilization of penicillin amidase (acylamide amidohydrolase, EC 3.5.1.4) from Escherichia coli was carried out on negatively charged particles of the water-soluble polyelectrolyte complex formed by poly(4-vinyl- N -ethylpyridinium bromide) and poly(methacrylic acid) in the ratio 1 : 3. The enzyme was covalently cross-linked to the polycation which was previously modified by cyanuric chloride. (2) Kinetic parameters of benzylpenicillin hydrolysis, catalyzed by immobilized penicillin amidase, were determined and it was shown that with a given method of immobilization, the catalytic efficiency of enzyme action changes slightly. The reaction proceeds in homogeneous aqueous solution without any diffusional difficulties. (3) Deformation of the pH optimum of catalytic activity, an increase of k cat in alkaline media and a sharp increase of the inhibition constant from 2 · 10 −5 to 1 · 10 −3 M caused by the product of the reaction (phenylacetic acid) show a remarkable effect of the negatively charged shell of the polyelectrolyte complex on kinetic parameters of the reaction. (4) Immobilization of the enzyme in polyelectrolyte complex particles leads to the appearance of new properties of the biocatalyst; immobilized penicillin amidase can be reversibly converted to the insoluble state with a slight change in pH and ionic strength of the solution. Transition of the enzyme into the insoluble state results in interruption of the reaction. The conditions for the phase separation of immobilized enzyme in solutions of salts are determined by the composition of polyelectrolyte complex and the nature of the low molecular weight electrolytes. Dissolution of the precipitate leads to quantitative recovery of the initial catalytic activity. (5) The self-regulating enzymatic system was simulated. Control of the activity in the system takes place according to the following scheme: accumulation of product → change in ionic strength of the solution → alteration of microenvironment of the enzyme → decrease in catalytic activity.

From triple interpolyelectrolyte-metal complexes to polymer-metal nanocomposites

Nanocomposite polymer materials containing metal or metal oxide particles attract growing interest due to their specific unique combination of physical and electric behavior. Stoichometric triple interpolyelectrolyte-metal complexes (TIMC) are insoluble in water and in aqueous organic media and may include high content of metal ions; concentration of ions is easy to vary in such polymeric systems. Reduction of metal ions is a common method for obtaining nanoparticles. Interpolyelectrolyte complexes reveal high permeability for polar low-molecular substances and salts. Such swelling behavior is important for the reduction of metal ions included in these solids. The properties of triple interpolyelectrolyte-metal complexes and preparation of nanocomposites from these materials using various methods of metal ion reduction are discussed in this work.

Advanced functional structures based on interpolyelectrolyte complexes

This review considers interpolyelectrolyte complexes, with a particular emphasis on advanced macromolecular co-assemblies based on polyionic species with nonlinear topology and on polymer–inorganic hybrids formed by interpolyelectrolyte complexes containing metal ions and/or metal nanoparticles.

Non-stoichiometric polyelectrolyte complexes: New, water soluble macromolecular compounds☆

Abstract Non-stoichiometri cpolyelectrolyte complexes (NSPELC) consisting of completely interacted polyelectrolyte pairs bearing opposite charges are examined. These are soluble in aqueous media, due to the presence of a sufficient number of free, ionized chain units which have not formed salt bonds between the chain, as a property. All the polyelectrolyte pairs are formed in the same way; it consists of mixing the two fully ionized compounds in the necessary proportions in the presence of a low mol. wt. salt. Where one of the components is present in excess and is a weak polyelectrolyte, water soluble NSPELC can be produced by titrating the incomplete reaction product with an acid or alkali until all the main chain units of the part present as excess are completely ionized. The molecular characteristics of the particles of such polyelectrolyte complexes (PELC) have been found to be independent of the synthesis method used. Proof of this is that the complex is present at an equilibrium.

The cooperation characteristics between polyelectrolytes during their reactions

A series of polyelectrolyte (PEL) systems have been used as examples to show that the conversion as a function of pH is a standard function over a wide range of initial PEL concentrations c0, and is independent of the latter. Electron microscopy and the rapid sedimentation method have been used to study the compositions of the complexes. The conclusion is reached that the reactions between PEL take place in autonomous micro-reactors.

Study of water soluble polyelectrolyte complexes of nonequimolar composition

A study has been made of the properties of polyelectrolyte complexes (PEC) of nonequimolar composition as exemplified by those formed by poly(N-ethyl-4-vinyl-pyridinium bromide) (PVP C2H5Br) and polymethacrylic acid (PMAA) in acid media. It has been found that such PEC have a property in common in that they dissolve in neutral and weakly basic media, whereas simple mixing of polyelectrolytes in any ratios at pH at which both polymer components are completely charged (pH ≈ 7) leads only to formation of equimolar PEC that are insoluble in water. The dissolution of PEC is observed over a sufficiently wide composition range 2·5 < PVPB:PMMA < 5, and does not involve dissociation of PEC into components. The mechanism of formation of water-soluble polycomplexes is considered, and a model of such polycomplexes is suggested.

Study of the structure of a polyacrylic acid-polyethyleneimine-copper (II) ternary polymer-metal complex

Abstract Spectrophotometry and EPR spectroscopy were used to investigate the structure of a polyacrylic acid-linear polyethyleneimine and Cu 2+ ion ternary polymer-metal complex and the structure of copper complexes with individual polymer ligands and their low molecular weight analogues. It was shown that either four amino groups of polyethyleneimine, or two amino groups of polyethyleneimine and two carboxylate groups of polyacrylic acid may form part of the coordination sphere of copper in the ternary complex. The proportion of structures of different types is determined by medium pH and the ratio of components.