Effect of copolymer composition on interpolymer complex formation of (co)poly(vinyl ether)s with poly(acrylic acid) in aqueous and organic solutions

The complex formation between vinyl ether of poly(ethylene glycol‐co‐vinyl butyl ether) with poly(acrylic acid) has been considered in aqueous and isopropanol solutions. The effect of copolymer composition on the complex formation process was clarified. It has been shown that the incorporation of hydrophobic fragments into macromolecules enhances the hydrophobic stabilization of polycomplexes in aqueous solutions. In organic media this effect disappears. The stability of polycomplexes formed both in aqueous and in organic solutions in respect to the addition of dimethylformamide has been studied.     

Fluorescence study of peptide and protein containing interpolyelectrolyte complexes

Four polyelectrolyte (PE)-protein and PE-peptide systems were selected for fluorescence experiments. The mode of binding of proteins to PE and structure of forming polycomplexes depends upon the ratio of components and chemical composition of polymer macromolecules. Complex formation of proteins with oppositely charged polycations is realized by the self-assembly of non-stoichiometric polycomplex particles with characteristic composition. These polycomplex particles have a rigid rod-like carcass structures in which protein molecules are practically exposed to the solvent. Two types of ternary polyanion-Cu²⁺-protein polycomplex particles are formed depending on the monomer composition of the copolymer. At higher content of hydrophobic N-isopropylacrylamide monomer unites, the protein globules in the structure of ternary polycomplex particles are densely covered by the shell of a polymer coil and practically “fenced of” from the water environment. At higher content of acrylic acid unites, polycomplex particles have more friable structures in which protein molecules are practically exposed to the solution. The PE-peptide conjugate species can be represented rather as a macromolecule of a segmented (block) copolymer in which the hydrophobic blocks, i.e. the sequences of copolymer and peptide unit pairs, which have formed the covalent and salt bonds alternate with hydrophilic ones, i.e. the sequences of the copolymer chain not participating in the formation of double strand blocks.     

Competitive complex forming reactions between monosubstituted and nonsubstituted poly(ethylene glycol)s with poly(methacrylic) acid

A competitive complex forming reaction between a number of monosubstituted poly(ethylene glycol)s (PEG*) containing a hydrophobic group of differing chemical nature and nonsubstituted PEG of various molecular weights with poly(methacrylic acid) (PMAA) was studied. A UV spectroscopy method was used. During the transfer of the hydrophobic chromophoric group from the aqueous medium into the hydrophobic domains of the polycomplex (PMAA.PEG*), a bathochromic effect was observed. The introduction of a hydrophobic group into the PEG chain leads to stabilization of the polycomplex (PMAA.PEG) that is formally the same as growing the chain length of PEG. The polymerization degree of PEG having the same competitive power as PEG* can be used as the peculiar scale of the complex forming ability of PEG* in the complexation with PMAA. © 1996 John Wiley & Sons, Inc.     

The effect of the initial ratio of components in the formation of a ternary interpolymer complex on its composition and structure

The effect of the initial ratio of components in the formation of ternary interpolymer complexes with low-molecular-mass compounds of various chemical natures on the compositions and structures of polycomplexes has been studied. Complexes based on aniline, 4,4′-dipyridyl, lysine, poly(acrylic acid), and the sodium salt of polyphosphoric acid have been examined. It has been shown that an increase in the content of poly(acrylic acid) in the pristine reaction system results in a relative gain in its content in the reaction product.     

Rheological properties of polycomplex gels of carboxymethyl cellulose with urea-formaldehyde oligomers

Structural and rheological properties of polycomplex gels of sodium carboxymethyl cellulose (Na-CMC) with urea-formaldehyde oligomers were studied at various component ratios at 298–343 K. The polycomplexes were examined by IR spectroscopy. Mechanical characteristics of solutions of Na-CMC and its complexes with urea-formaldehyde oligomers and the size of structural units of these solutions were determined.     

Hydrogels based on polycarboxylic acid-agar-agar complexes

IR spectroscopy and viscometry data have shown that poly(acrylic acid) and poly(methacrylic acid) form complexes with agar-agar in aqueous solutions as they do with other polysaccharides. The polyacid-agar-agar complexes are typical hydrogels. The swelling index of hydrogels based on the poly(methacrylic acid)-agar-agar complex has been found to be markedly lower than that of poly(acrylic acid)-agaragar complex. The hydrogels based on the complex of cross-linked poly(acrylic acid) with agar-agar can be of practical interest as polymeric carriers for drugs.     

Novel temperature‐responsive water‐soluble copolymers based on 2‐hydroxyethylacrylate and vinyl butyl ether and their interactions with poly(carboxylic acids)

Novel water‐soluble amphiphilic copolymers have been synthesized by free radical copolymerization of 2‐hydroxyethylacrylate with vinyl butyl ether. In water these copolymers exhibit lower critical solution temperature, which depends on the content of hydrophobic vinyl butyl ether units. The interaction between these copolymers and poly(acrylic acid) or poly(methacrylic acid) in aqueous solutions results in formation of interpolymer complexes stabilized by hydrogen bonds and hydrophobic interactions. An increase in hydrophobicity of the copolymers leads to the enhancement of their complex formation ability with respect to poly(acrylic acid) and poly(methacrylic acid). Poly(methacrylic acid) forms stronger complexes with the copolymers when compared with poly(acrylic acid). The complexes exhibit dual sensitivity to pH‐ and temperature and this property may be easily adjusted regulating the strength of interaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 195–204, 2006     

Formation of Fe2+-phenanthroline complexes in the volume of hydrogel

The interaction of weakly crosslinked gels of poly(methacrylic acid) and a nonionic gel based on N-vinylcaprolactam and N-vinylimidazole with Fe²⁺ ions in aqueous solutions has been studied. A comparative study of the conformational state and of the absorption ability of the gels for their interaction with iron and ferroin ions has been performed. It has been shown that Fe²⁺ ions are efficiently absorbed by both poly(methacrylic acid) gels and the gels based on N-vinylcaprolactam and N-vinylimidazole. In this case, the poly(methacrylic acid) gels undergo contraction, while nonionic gels derived from N-vinylcaprolactam and N-vinylimidazole experience swelling. During the interaction of gels containing immobilized Fe²⁺ ions with phenanthroline, the efficient absorption of the complexon and the formation of Fe²⁺-phenanthroline complexes in the gel volume take place, thus inducing the contraction of gels. The interaction of poly(methacrylic acid) gels with ferroin is accompanied by the absorption of the complex, the formation of the tertiary complexes, and the collapse of the gel. The efficiency of formation of tertiary complexes in the gel volume is independent of their preparation procedure.     

“Recognition” of copolymers and stereoisomers in macromolecule complexation reactions in dilute solutions

Theoretical relationships have been obtained describing the dependence of selectivity (or molecular “recognition”) on the length of reacting polymer chains in reactions between complementary macromolecules. The possibility of highly efficient separation of mixtures of macromolecules, differing little in chemical structure, was predicted as well as of fractionation of compositionally inhomogeneous copolymers by means of polymer-polymer interactions. Experimentally it has been found that polyethylene glycol mixed with polymethacrylic acid stereoisomers is selectively bound in a polycomplex with macromolecules enriched with iso-triads; polyvinylpyrrolidone is selectively bound to those poor in iso-triads. Polyvinylpyrrolidone selectively binds polymethacrylic acid in mixtures with copolymers of acrylic and methacrylic acids. The degree of “recognition” of a macromolecule of given chemical structure by an oligomer increases with increasing oligomer chain length and is in a quantitative agreement with the theoretical equation. It has been shown that, in aqueous solution for interaction of polyacrylic acid with compositionally inhomogeneous copolymer of 4-vinylpyridine and N-ethyl-4-vinylpyridinium bromide (partially quaternized polyvinylpyridine), the polyacrylic acid binds selectively the fractions rich in non-alkylated units. This result can be explained quantitatively in terms of the theory.     

聚甲基丙烯酸与修饰聚丙烯酰胺间的络合作用

利用荧光各向异性,荧光探针和荧光猝灭等静态光物理技术研究了稀水溶液中聚甲基丙烯酸（ＰＭＡＡ）与阳离子修饰聚丙烯酰胺（ＱＣＰＡＭ）间的络合作用。结果表明：在ｐＨ＝２－８范围内,ＰＭＡＡ与ＱＣＰＡＭ之间发生明显络合,但以ｐＨ为４时络合作用最大,最佳络合本比为１：１（单体单元比）,络合作用的发生大大地改变了ＰＭＡＡ的构象行为,ＰＭＡＡ构象对ｐＨ和络合作用的双重依赖性有可能在新型“智能”凝胶的设计合成上获     

Pseudotemplate synthesis of copper nanoparticles in solutions of poly(acrylic acid)-pluronic blends

It was found that the reduction of copper(II) ions in solutions of poly(acrylic acid)-pluronic blends results in a stable sol of metallic copper with a particle size below 10 nm, whereas a less stable sol with coarse aggregates of particles is formed in the presence of poly(acrylic acid) alone and an insoluble complex of this polymer with copper nanoparticles is produced in the presence of pluronic alone. The addition of poly(acrylic acid) to the complex causes the transfer of a portion of nanoparticles from the precipitate into the sol. In mixed poly(acrylic acid) and pluronic solutions, no formation of a polymeric complex with reasonable stability was detected. It was assumed that such a polycomplex is stabilized in the presence of copper nanoparticles. Owing to its amphiphilic nature, the complex forms stable protective shields on the surface of nanoparticles, and the stability of the sol is determined by free fragments of poly(acrylic acid).     

Block copolymer micelles in aqueous media

Polystyrene-block-poly(methacrylic acid) and poly(methacrylic acid)-block-polystyrene-block-poly(methacrylic acid) di- and triblock copolymers form micelles with polystyrene cores and poly(methacrylic acid) shells when dissolved in water/1, 4-dioxane mixtures, rich in dioxane. These micelles can be transferred into water rich mixtures, into water, and into aqueous buffers by stepwise dialysis. Quasielastic light scattering and sedimentation velocity experiments show that in dioxane rich mixtures exists a dynamic micellization equilibrium, while in dioxane poor solutions and in aqueous buffers the equilibrium is frozen. The process of mixed micelles formation was observed in dioxane rich solutions.     

Study of interaction between two oppositely charged polyelectrolytes and formation of polyelectrolyte complexes

Polyelectrolyte complex formation has been studied between oppositely charged polyelectrolytes, e.g., polyethylene-imine, polymethacrylic acid, and methacrylic acid–methacrylamide copolymer. Formation of complexes could be shown through several experimental techniques, e.g., viscometry, conductometry, potentiometry, and IR spectra. It is suggested that these complexes are perhaps formed as a result of electrostatic cooperative interaction and a “ladder-like” interaction is likely to be more favorable.     

Thermodynamic characteristics and the temperatures of relaxation transitions of poly(methacrylic acid)

The heat capacity of poly(methacrylic acid) containing 2.5 wt % water was measured in a vacuum adiabatic calorimeter at temperatures between 80 and 325 K. The heat capacity of anhydrous poly(methacrylic acid) was calculated, and its standard enthalpies of combustion and formation were determined. On the basis of the enthalpy of melting of the “free”-water phase, the limit of water solubility in the polymer was found calorimetrically at 273 K. The temperatures of relaxation transitions (the glass transition and the β and γ transitions) of poly(methacrylic acid) mixtures with water were determined via differential thermal analysis in the region 80–550 K. In addition, the determination of the temperatures of transitions of anhydrous poly(methacrylic acid) was performed via extrapolation to zero water content of the concentration dependences of the relaxation-transition temperatures.     

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 Crystal Violet and Polyanions in Aqueous Solution

The effect of several polyelectrolytes on the absorption spectrum of crystal violet (CV) has been studied over a wide range of pH. The following polymers were used: isotactic poly(methacrylic acid), PMA_i; conventional poly(methacrylic acid), PMA_c; a methacrylic acid (80%)-styrene (20%) copolymer, PMAS; and poly(styrene sulfonic acid), PSSA. Distinctly different effects were observed in the four cases. This has been interpreted in terms of a dependence of the degree and mode of binding of cationic dye molecules onto the polyacids on the hydrophobicity of the macroions.     

Peculiarities of Formation of Intermolecular Polycomplexes Based on Polyacrylamide,Poly(vinyl alcohol) and Poly(ethylene oxide)

The phenomenon of self-assembly of aggregates formed by relatively short chains of poly(vinyl alcohol) (PVA) on the long macromolecules of polyacrylamide (PAA) in aqueous medium are discussed. PVA and PAA form intermolecular polycomplexes (InterPC) of a constant composition independently on a ratio of polymer components. The complex formation between high-molecular-weight PAA and relatively low-molecular-weight poly(ethylene oxide) (PEO) are considered also. PEO with M ⩽ 4·10⁴ g.mol⁻¹ weakly interacts with PAA. The polymer-polymer interaction can be intensified when the part of amide groups (∼20 mol %) on PAA chain to transform into the carboxylic groups. InterPCs formed by PEO and initial or modified PAA have associative structure with friable packing of the polymer segments. They are stabilized by the hydrogen bond system.     

Thermodynamics of Swelling of Polyacrylamide and Poly(methacrylic acid) Lyophilized Xerogels in Water

The structure and thermodynamic functions of water mixing with polyacrylamide and poly(methacrylic acid) xerogels prepared via drying of chemically crosslinked hydrogels equilibrium swollen in water are studied by methods of scanning electron microscopy, low-temperature nitrogen adsorption, differential scanning calorimetry, isothermal interval sorption of water vapor, and microcalorimetry. The liquid-phase drying in air at 70°C and solid-phase lyophilic drying under vacuum are used. Samples dried by different methods have dissimilar structures, which significantly affects the thermodynamics of the interaction of xerogels with water. The Flory–Huggins parameter of interaction of polyacrylamide and poly(methacrylic acid) with water and also its enthalpy and entropy components are independent of the procedure of xerogel preparation. The influence of the latter component manifests itself only in the thermodynamics of the relaxation of the nonequilibrium glassy structure of polymer.     

The complex formation between polyacrylamide containing glycine end groups and bovine serium albumin in the presence of copper (II) in neutral aqueous media

Complex formation between end group containing polyacrylamide and BSA has been studied in neutral water. Water soluble and insoluble complexes are formed when divalent copper ions are added to the solution.The contacts between protein and polyelectrolyte are achieved via chelate unit formation in which the copper ion is attached at the center. The solubility of the polycomplexes depends on protein/polymer ratio. Starting with very low concentration of protein in the system, phase separation takes place. Above the critical ratio of the protein/polymer, the mixture again exhibits water soluble character. The velocity of the formation of insoluble ternary complexes has been investigated by spectrophotometric method at different reaction conditions (preparation of mixture, ratio of components, low molecular salts, temperature and stirring, molecular weight of polyelectrolyte and Cu²⁺ concentration). A hypothetical structural scheme for the formation of soluble and insoluble ternary polycomplexes is proposed.     

pH effects on the complexation, miscibility and radiation-induced crosslinking in poly(acrylic acid)-poly(vinyl alcohol) blends

The effect of pH on the complexation of poly(acrylic acid) with poly(vinyl alcohol) in aqueous solution, the miscibility of these polymers in the solid state and the possibility for crosslinking the blends using gamma radiation has been studied. It is demonstrated that the complexation ability of poly(vinyl alcohol) with respect to poly(acrylic acid) is relatively low in comparison with some other synthetic non-ionic polymers. The precipitation of interpolymer complexes was observed below the critical pH of complexation (pH(crit1)), which characterizes the transition between a compact hydrophobic polycomplex and an extended hydrophilic interpolymer associate. Films prepared by casting from aqueous solutions at different pH values exhibited a transition from miscibility to immiscibility at a certain critical pH, pH(crit2), above which hydrogen bonding is prevented. It is shown here that gamma radiation crosslinking of solid blends is efficient and only results in the formation of hydrogel films for blends prepared between pH(crit1) and pH(crit2). The yield of the gel fraction and the swelling properties of the films depended on the absorbed radiation dose and the polymer ratio. [Diagram: see text] SEM image of an equimolar PAA-PVA blend cast from a pH 4.6 solution.