INTERPOLYMER ASSOCIATION OF ACRYLAMIDE COPOLYMERS WITH POLY(ETHYLENEIMINE): STABILITY,THERMODYNAMIC PARAMETERS,AND THEIR CORRELATION WITH THE COPOLYMER MICROSTRUCTURE

Acrylamide/vinyl acetate and acrylamide/vinyl propionate copolymers were prepared by solution polymerization using benzoyl peroxide as the initiator. The copolymer composition was determined from the percent nitrogen in the copolymers.

The stability constants and related thermodynamic parameters (e.g., ΔG°, ΔH°, and ΔS°,) of the interpolymer complexes with Poly(ethyleneimine) were determined by using Osada's method. These parameters have been correlated with the sequence distribution of monomer units in the copolymer chains which were obtained from ¹³C{¹H} NMR spectroscopy. The sequence distribution of the comonomer units in the copolymer chains influence the association between the copolymers and the polyelectrolyte which is reflected on the stability of the interpolymer complexes.     

Selective Interpolymer Complexation between Acrylic Copolymers and Nonionic Polymers

Abstract

Selective interpolymer complexation has been studied between methacrylic acid-methacrylamide copolymer and some complementary polymers such as poly(methacrylamide), poly(vinyl pyrrolidone), and poly(ethylene oxide). The relative order of complexation ability of the various nonionic polymers has been interpreted on the basis of the nature of interactions between different units of polymers. Configurational environment and neighboring group influences seem to affect interpolymer complex formation.     

Interpolymer complex formation of some nonionogenic polymers with linear and crosslinked polyacrylic acid

The formation of interpolymer complexes on the surface of crosslinked poly (acrylic acid) with some nonionogenic polymers is compared with the complex formation in analogous linear polymer systems. The behavior of these systems is compared with that of complexes of two oppositely charged polyelectrolytes. The concentration redistribution of the linear polymer in the system polyelectrolyte network-polymer solution and the degree of swelling of this network in these solutions were determined. © 1994 John Wiley & Sons, Inc.     

Macromolecular helicity induction in a cationic polyacetylene assisted by an anionic polyisocyanide with helicity memory in water: replication of macromolecular helicity

We report the first example of the replication of macromolecular helicity. An optically active helical and anionic polyelectrolyte, the sodium salt of poly(4-carboxyphenyl isocyanide), was found to serve as the template for further helicity induction in a different polyelectrolyte with opposite charges in water, resulting in interpolymer helical assemblies with controlled helicity. The effects of the pH and salt concentration on the helicity induction were investigated.     

Complexation of copper(II) ions with imidazole–carboxylic polymeric systems

The interaction of two polyampholyte systems, poly(1‐vinylimidazole‐co‐acrylic acid) and interpolymer complex poly(acrylic acid)/poly(1‐vinylimidazole) with copper(II) ions in water, was examined with potentiometry (pH‐metry and Cu‐selective electrode) and electron spin‐resonance spectroscopy. Coordination of Cu²⁺ with copolymer proceeded by carboxylic groups, whereas the interpolymer system azole units were also involved in the inner sphere of the complex. Synergism between coordination with metal ions and intramolecular hydrogen or ionic bonds was shown. The interpolymer complex was an effective system for binding, extracting, and concentrating copper ions from water. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2256–2263, 2003     

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 n _s^cr is achieved, the dimensions of the complex increase abruptly. At this concentration, macromolecules involved in the complex begin to separate, and at concentration n _s^*, 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, n _s^cr, 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.     

Electrostatic free energy of weakly charged macromolecules in solution and intermacromolecular complexes consisting of oppositely charged polymers

When oppositely charged polyelectrolytes are mixed in water, attraction between oppositely charged groups may lead to the formation of polyelectrolyte complexes (associative phase separation, complex coacervation, interpolymer complexes). Theory is presented to describe the electrostatic free energy change when ionizable (annealed) (macro-)molecules form a macroscopic polyelectrolyte complex. The electrostatic free energy includes an electric term as well as a chemical term that is related to the dissociation of the ionic groups in the polymer. An example calculation for complexation of polyacid with polybase uses a cylindrical diffuse double layer model for free polymer in solution and electroneutrality within the complex and calculates the free energy of the system when the polymer is in solution or in a polyelectrolyte complex. Combined with a term for the nonelectrostatic free energy change upon complexation, a theoretical stability diagram is constructed that relates pH, salt concentration, and mixing ratio, which is in qualitative agreement with an experimental diagram obtained by Bungenberg de Jong (1949) for complex coacervation of arabic gum and gelatin. The theory furthermore explains the increased tendency toward phase separation when the polymer becomes more strongly charged and suggests that complexation of polyacid or polybase with zwitterionic polymer (e.g., protein) of the same charge sign (at the "wrong side" of the iso-electric point) may be due (in part) to an induced charge reversal of the protein.     

高分子复合物的研究与应用进展

两种大分子可以利用氢键或者库仑力形成高分子复合物,根据不同的作用力性质可分为氢键复合物(氢键作用)和聚电解质复合物(静电力)。这种通过物理共混得到的高分子复合物,表现出了与单组分高分子截然不同的性质和特点。这一特性决定了此类复合物在诸多领域的应用,目前应用较多的领域有生物医药、渗透汽化、增稠等。本文主要介绍了高分子复合物近年来研究和应用的进展情况。     

Light scattering studies on polyelectrolyte complexes

The Coulomb interaction between oppositely charged polyelectrolytes leads to spontaneous formation of interpolymer complexes. Such complexes are of high practical relevance, but also interesting objects of fundamental research. The level of aggregation depends on the nature of the components as well as on the medium and external conditions of the polyelectrolyte complex formation. An appropriate combination of methods provides detailed information on the stoichiometry and structure of such systems. Especially, light scattering techniques proved to be a powerful tool in studying the structure and behavior of the complexes in solution. Selected examples will demonstrate the efficiency of such investigations.     

The formation of interpolymer complexes in mixtures of weak polyelectrolytes

How the specific features of the formation of interpolymer complexes in nonstoichiometric mixtures of weak and strong polyelectrolytes depend on their concentrations, their degrees of polymerization, the polyelectrolyte weakness, and the low-molecular-mass salt concentration were investigated. Theoretical results are in qualitative accordance with experimental data.     

Conjugated Polyelectrolyte-Ag+ Fluorescent Switch for Biothiol Sensing

A new "off-on" switch for sensitive and selective fluorescence detection of biothiols[glutathione(GSH), cysteine(Cys) and homocysteine(Hcy)] was developed based on an anionic conjugated polyelectrolyte(CPE), pyridyl-functionalized poly(phenylene ethynylene)(P1). The fluorescence of P1 can be significantly quenched by Ag⁺ due to complexation-mediated interpolymer aggregation. Furthermore, biothiols can efficiently recover the fluorescence intensity of P1 as a result of the stronger binding between thiol group and Ag⁺, which dissociates P1 from the P1/Ag⁺ complex and disrupts interpolymer aggregation. Under optimum conditions, a good linear relationship in a range of 100―4200 nmol/L is obtained for GSH with a detection limit of 80 nmol/L(S/N=3). As a result of specific interaction between the thiol group and Ag⁺, the proposed method shows a high selectivity for biothiols. In addition, the CPE-based fluorescence "off-on" switch has been used to quantitatively detect total biothiols in cell lysates.     

Effect of chain compositions on interpolymer specific interaction in solutions

An interpolymer specific interaction of polymers with complementary proton donor units and proton acceptor units was studied with viscometry. In this study, poly(styrene-co-octyl acrylate-co-acrylic acid) as proton donating polymer (PDP) and poly(styrene-co-octyl acrylate-co-4-vinylpyridine) as proton accepting polymer (PAP) with different macromolecular chain compositions were prepared by emulsion copolymerization. Complexed solutions formed by PDP and PAP were studied with a novel interaction criterion k_a based on viscosity enhance factor. The effects of macromolecular chain compositions on the ability to interpolymer interaction and complex stoichiometry were discussed. The results showed that long chain alkyl acrylate units play an important role in the interpolymer specific interaction.     

Photophysical investigations of interpolymer interactions in solutions of a pyrene substituted poly(acrylic acid), poly(vinyl amine), poly(1-aminoacrylic acid), and poly(1-acetylaminoacrylic acid)

Photophysical properties of the pyrene chromophore covalently bound to poly(acrylic acid) were used to investigate the interactions of a pyrene substituted poly(acrylic acid) (1) with poly(vinyl amine hydrochloride) (PVAm), poly(1-aminoacrylic acid) (PDA), and poly(1-acetylaminoacrylic acid) (PADA) in aqueous solutions. A number of photophysical parameters were obtained from fluorescence emission and excitation spectra, the deconvolution of decay curves for pyrene monomer, and excited state complex fluorescence and the quenching of pyrene monomer fluorescence by nitromethane in polymer solutions. These photophysical parameters were considered to reflect the inter- and intrapolymer interactions in solutions of 1 , PVAm, PDA, and PADA. The formation of interpolymer complexes between 1 and PVAm was noticed at low (< 4) as well as high (> 8) values, whereas PDA and 1 formed interpolymer complexes at low pH only. No interpolymer complex formation was detected in solutions of 1 and PADA under low or high pH conditions. The structures of interpolymer complexes formed between 1 and PVAm under low and high pH conditions were found to be determined by the conformation of 1 . There were significant differences in the interpolymer interactions of 1 and PDA in comparison to those of 1 and PVAm; in particular, the fluorescence from the excited state complex was enhanced in solutions of 1 and PVAm but quenched in solutions of 1 and PDA. The investigations of terpolymer solutions of 1 , PVAm, and PADA indicated that the nature of interpolymer complexes formed in terpolymer solutions was determined by Coulombic interactions of the amino and carboxylic group containing polymers.     

Interpolymer complexes of copolymers of vinyl ether of diethylene glycol with poly(acrylic acid)

 The complex formation reactions of poly(vinyl ether of diethylene glycol) as well as vinyl ether of diethylene glycol–vinyl butyl ether copolymers with poly(acrylic acid) have been studied in aqueous and alcohol solutions. The formation of interpolymer complexes which were stabilized by hydrogen bonds was shown. The effects of molecular weight of poly(acrylic acid) and the nature of the nonionic polymer on the composition and stability of interpolymer complexes were clarified. The critical pH values of complexation were determined for different systems with various molecular weights and hydrophobic–hydrophilic balances. The stability of the interpolymer complexes formed in aqueous and alcohol solutions with respect to dimethylformamide addition was evaluated. The role of hydrophobic interactions and the presence of active groups on stability of the interpolymer complexes is discussed. Received: 23 July 2001 Accepted: 27 September 2001     

Solvent effects on the formation of nanoparticles and multilayered coatings based on hydrogen-bonded interpolymer complexes of poly(acrylic acid) with homo- and copolymers of N-vinyl pyrrolidone

The formation of hydrogen-bonded interpolymer complexes between poly(acrylic acid) and poly(N-vinyl pyrrolidone) as well as amphiphilic copolymers of N-vinyl pyrrolidone with vinyl propyl ether has been studied in aqueous and organic solutions. It was demonstrated that introduction of vinyl propyl ether units into the macromolecules of the nonionic polymer enhances their ability to form complexes in aqueous solutions due to more significant contribution of hydrophobic effects. The complexation was found to be a multistage process that involves the formation of primary polycomplex particles, which further aggregate to form spherical nanoparticles. Depending on the environmental factors (pH, solvent nature), these nanoparticles may either form stable colloidal solutions or undergo further aggregation, resulting in precipitation of interpolymer complexes. In organic solvents, the intensity of complex formation increases in the following order: methanol < ethanol < isopropanol < dioxane. The multilayered coatings were developed using layer-by-layer deposition of interpolymer complexes on glass surfaces. It was demonstrated that the solvent nature affects the efficiency of coating deposition.     

Interaction of PEO-PS-PEO Block Copolymers with Ionic Surfactants in Aqueous Solution

Abstract

The formation of polyelectrolyte type complex by the interaction between ionic (anionic and cationic) surfactant and block copolymer in water was observed from viscosity measurements. Interaction between the two was also examined from conductance and surface tension measurements were two transitions, one below and one above the critical micelle concentration, CMC, of the surfactants were observed. A possible mechanism for such an interaction is proposed.     

Studies on the structural transitions and self-organization behavior of polyacrylic acids with complementary polymers in aqueous solution by laser flash photolysis method using the triplet state of covalently bound phenosafranine

The conformational transition of polyacrylic acids and the formation of interpolymer complexes with synthetic polymers in aqueous solution are investigated using the triplet state of the cationic dye phenosafranine covalently attached to the polymer chain. Laser excitation of the phenosafranine dye covalently bound to polymethacrylic acid at 532 nm shows that the absorption spectrum of the triplet state shifts to red region by 40 nm as compared to that of the free dye in aqueous solution and the triplet state lifetime is enhanced by 20-fold. Laser flash excitation shows that the environment of the triplet state of the dye bound to the polyelectrolyte at pH ?5.5 in aqueous solution is more rigid and less polar resulting in a highly compact globular nature of the polymer. The decay of the triplet state of the dye bound to the polymer is attributed to the quenching of the excited state by the carboxylate groups of polyacrylic acids and to the decay process of the triplet in the tightly coiled polymer environment in the pH range 2.0–5.0. The spectra of the triplet dye molecules bound to the polymer at different degree of ionization of the polyelectrolyte suggest that the structural transition from compact globular structure to stretched rod like structure is cooperative involving a series of structural transitions. The observation of diprotonated triplet state of the PMAA bound dye at higher pH (i.e. pH ∼7.0) reveals the existence of an intermediate structure akin to a micellar segment in PMAA prior to the formation of elongated linear chain. The self-organization of PMAA adduct formation with complementary macromolecules, PVP, PEO and PVA primarily due to hydrogen bonding makes the environment of the dye in the adduct more compact and rigid; in particular poly(vinylpyrrolidone), PVP, has the tendency to form more compact interpolymer complex at pH 4.5 than poly(vinyl alcohol), PVA, and poly(ethylene oxide), PEO as revealed from the laser flash photolysis studies of the polymer bound dye using triplet state of the phenosafranine as the marker.     

Interpolymer complex between poly(ethylene oxide) and poly(carboxylic acid)

An interpolymer complex was prepared by mixing aqueous solutions of poly(ethylene oxide) (PEO) and of a poly(carboxylic acid), i.e., poly(acrylic acid)(PAA), poly(methacrylic acid)(PMAA), or styrene-maleic acid copolymer(PSMA). The complexation mechanism was discussed on the basis of results of such experimental methods as viscosity, potentiometric titration, and turbidimetry. The hydrogen bond is primarily involved in these complexations, but the influence of hydrophobic interaction on complexation can not be ignored. If the degree of dissociation α of carboxylic acid or the degree of polymerization P_n of PEO was perceptibly changed, a stable complex was obtained at about α 0.1 or P_n (PEO) = 40 for PMAA, 200 for PAA. This fact indicates that more than a definite number of binding sites are necessary for a stable interpolymer complex to be formed and that cooperative interaction among active sites plays an important role in complex formation.     

Interpolymer complexes of poly(N-vinylpyrrolidone) with copolyimide-grafted side chains of poly(methacrylic acid)

The process of formation and structural organization of interpolymer complexes formed by macromolecules of poly(N-vinylpyrrolidone) and poly(methacrylic acid) chains grafted onto polyimide in solution is investigated via the method of polarized luminescence. A luminescent label of anthracene structure is covalently bound to both polymers. Relaxation times characterizing intramolecular mobility of each of the components in their interpolymer complex are measured in relation to the composition of the system.     

Sources of Soil and Plant Contamination in an Urban Environment and Possible Assessment Methods

Abstract

A survey was carried out in the city of Brno, Czech Republic in order to determine the levels and sources of soil and plant contamination and the possible implications for human health. A group of 136 topsoil and plant samples were taken in a defined sampling pattern, both in urban (in the year 1991) and suburban (1992) areas, paying particular attention to traffic density and intensity of land use. Samples were analysed for the contents of six heavy metals (Cd, Cu, Cr, Ni, Pb, Zn) and polycyclic aromatic hydrocarbons. The main soil characteristics were also determined (p^H, CEC, C_ox).

Traffic influence indices (TII) were calculated for each locality based on the traffic density and micro climatic conditions. Soil pollution indices (SPI) and plant pollution indices (PPI) were defined as a loading of a group of toxic metals relative to acceptable upper limits and were used as a general measure of the soil and plant burden at a particular site.

There were significant differences between the level of pollution in urban and suburban areas particularly for Pb, Cr and Ni in plants.

Traffic was found to be the major source of pollution by Pb, Zn and Cu in the urban survey and significant correlations were found between soil Pb × TII and SPI × TII in urban area. No such relationships were found for the suburban samples.