Formation Of Interpolymer Complexes Research Articles

Effect of the Formation of Hydrophilic and Hydrophobic-Hydrophilic Associates on the Behavior of Copolymers of N-Vinylpyrrolidone with Methyl Acrylate in Aqueous Solutions.

It has been shown that there exist conditions under which thermosensitive copolymers of N-vinylpyrrolidone with methyl acrylate form hydrophobic-hydrophilic associations, which are unstable dynamic meshes, the bonds in which are continuously broken and created again, and the nature of the formation of such meshes depends significantly on the proportion of the hydrophobic component in the copolymer. It is shown that the interaction of the above copolymers with polyacrylic acid results in the formation of not only classical interpolymer complexes, but also hydrophilic interpolymer associates, which also represent unstable networks existing in a dynamic mode. In such meshes, the molecules of the above copolymers serve as a kind of cross-agent connecting the polyacid molecules. There are also conditions under which such meshes acquire a complex structure, since unstable bonds between macromolecular tangles of both the same and different types take part in their formation. It is shown that the transition from the formation of interpolymer complexes to the formation of hydrophilic interpolymer associates can occur, among other things, due to changes in the acidity or concentration of low-molecular salt in solution.

СУДА ЕРИТІН ПОЛИМЕРЛЕР МЕН ОЛАРДЫҢ ПОЛИКОМПЛЕКСТЕРІНІҢ СУЛЫ ЕРІТІНДІДЕГІ ҚАСИЕТТЕРІ

Abstract. The interaction of oppositely charged polyelectrolytes (sodium salt of carboxymethylcellulose (NaCMC), methylcellulose (MC), polyethylenimine (PEI) and polydimethyldiallylammonium chloride (PDMDAAС), and unifloc (UF)) in an aqueous environment was studied using the methods of viscometry, spectrophotometry and macroelectrophoresis. It has been established that the interaction of these polyelectrolytes is accompanied by a significant decrease in reduced viscosity (up to 0.1-0.15 dl/g, which is typical for compacted macromolecules of globular proteins), an increase in optical density and an inversion of the sign of the electrokinetic potential. All this indicates the formation of interpolymer complexes from interacting cationic and anionic polyelectrolytes. Experimental results of studying the properties of water soluble polymers and their polyelectrolyte complexes in aqueous solutions at the water/air interface are described and discussed. It has been shown that complex formation in relatively simple systems is accompanied by changes in the pH of the medium, optical, hydrodynamic, electrochemical and other properties of macromolecules. In the systems we studied, the interaction of the system components is not accompanied by variations in the pH of the medium, therefore, information about the interaction of water-soluble polyelectrolytes in the systems we studied was obtained based on viscometric and spectrophotometric titration data, as well as from changes in the electrokinetic potential of macromolecules. The study of the electrokinetic potential showed that the formation of interpolymer complexes in the systems under consideration is accompanied by significant changes in the electrokinetic potential of macromolecules. A study of the properties of mixtures of aqueous solutions of Na-CMC, MC, UF with polydimethyldiallylammonium chloride and polyethylenimine indicates the formation of interpolyelectrolyte complexes that have a more compact structure than the original macromolecules. Key words: polyelectrolytes; flocculation; cross-linking; stability; interpolymer complexes; optical density; polymer.

Biomolecular Complexation on the "Wrong Side": A Case Study of the Influence of Salts and Sugars on the Interactions between Bovine Serum Albumin and Sodium Polystyrene Sulfonate.

In the protein purification, drug delivery, food industry, and biotechnological applications involving protein–polyelectrolyte complexation, proper selection of co-solutes and solution conditions plays a crucial role. The onset of (bio)macromolecular complexation occurs even on the so-called “wrong side” of the protein isoionic point where both the protein and the polyelectrolyte are net like-charged. To gain mechanistic insights into the modulatory role of salts (NaCl, NaBr, and NaI) and sugars (sucrose and sucralose) in protein–polyelectrolyte complexation under such conditions, interaction between bovine serum albumin (BSA) and sodium polystyrene sulfonate (NaPSS) at pH = 8.0 was studied by a combination of isothermal titration calorimetry, fluorescence spectroscopy, circular dichroism, and thermodynamic modeling. The BSA–NaPSS complexation proceeds by two binding processes (first, formation of intrapolymer complexes and then formation of interpolymer complexes), both driven by favorable electrostatic interactions between the negatively charged sulfonic groups (−SO3–) of NaPSS and positively charged patches on the BSA surface. Two such positive patches were identified, each responsible for one of the two binding processes. The presence of salts screened both short-range attractive and long-range repulsive electrostatic interactions between both macromolecules, resulting in a nonmonotonic dependence of the binding affinity on the total ionic strength for both binding processes. In addition, distinct anion-specific effects were observed (NaCl < NaBr < NaI). The effect of sugars was less pronounced: sucrose had no effect on the complexation, but its chlorinated analogue, sucralose, promoted it slightly due to the screening of long-range repulsive electrostatic interactions between BSA and NaPSS. Although short-range non-electrostatic interactions are frequently mentioned in the literature in relation to BSA or NaPSS, we found that the main driving force of complexation on the “wrong side” are electrostatic interactions.

Solutions of polymer blends in highly saline water: Salt-induced inversions of viscosity effects for poly(ethylene oxide) + poly(sodium 4-styrenesulfonate)

Solution viscosities were measured for an uncharged polymer [poly(ethylene oxide): PEO], for a polyelectrolyte [poly(sodium 4-styrenesulfonate): PSS-Na] and for the blends of these components in water of variable salinities. The evaluation of these data with respect to the intrinsic viscosities revealed the following: for NaCl as extra salt, the intrinsic viscosities of the blends are always less than predicted by additivity; moreover the [η] values of PEO increase with rising salinity of the solvent, in contrast to that of PSS-Na which decrease. This situation leads to an inversion point of the salt effects at the salinity of approximately 2.9 mol/L. This finding becomes comprehensible by treating the salt solutions as mixed solvents. Replacing NaCl by the CaCl2 (divalent cation) as extra salt leads to the [η] values for the blends, which are larger than additive. Based on phenomenological thermodynamic consideration this behavior is attributed to an entropy driven formation of interpolymer complexes and explained in molecular terms.

Interpolymer Complexes of Synthetic, Natural and Semi-Natural Polyampholytes: A Review

This review is focused on synthetic, natural and semi-natural polyampholytes and their ability to form interpolymer complexes with other polyelectrolytes and non-ionic polymers. It provides definition, classifica-tion and overview of physicochemical properties of polyampholytes. The conformation and phase behaviour of intrinsically disordered proteins and semi-natural polyampholytes derived from aminoacids is discussed. The ability of synthetic, natural and semi-natural polyampholytes to form interpolymer complexes with wa-ter-soluble polymers is considered. Most of the research in this area is focused on interpolyelectrolyte com-plexes of polyampholytes with oppositely charged polyelectrolytes; however, there are also studies demon-strating the formation of hydrogen-bonded complexes. The nature of the complexation is often affected by so-lution pH and also isoelectric point of polyampholytes. The complexation between polyampholytes and other polymers may lead to formation of colloidal dispersions (nano- and microparticles), liquid-liquid phase sepa-ration (called complex coacervation), fully soluble polycomplexes or physically cross-linked gels. A substan-tial body of studies in this area was focused on the complexes formed by proteins. Application of interpolymer complexes formed by polyampholytes in biotechnology, medicine, encapsulation technologies, separation science, biocatalysis, food science and pharmaceutics is discussed.

Current state of the problem of soil protection and prospect of using humic acids

The article reviews the literature on the state of the problem of protecting the soil cover of the earth. Today, during the period of strong pollution of the lithosphere by technogenic wastes of various nature, leading to soil degradation and erosion, in measures to improve the physical, chemical, hydrological, agronomic and other properties of soils, preference should be given to the least harmless natural raw materials. These include humic acids (HA) and their derivatives, which are good adsorbents, stabilizers and fixers of dispersed systems. The study of the composition of humic acids with various water-soluble polymers and surfactants is another not fully understood area of interdisciplinary nature. Literary search for the works of Kazakh scientists shows the underdevelopment of both the extraction of humic acids and the formation of HA interpolymer complexes (IPC) with polymers and surfactants, as well as their use as fixers, structure formers of soils subject to wind and water erosion. Having large reserves of coal in the republic, a source of humic acids, it is not forgivable not to develop an integrated approach to research on the extraction of HAs, the formation of IPC on their basis and the use of new structure-forming agents to improve the degraded soils of the republic's structures.

Interpolymer Complexes of Star-Shaped Copolymers of Polyoxazoline with the Calixarene Core and Linear Polyacids in Solution

Star-shaped polymers with the calix[8]arene core and poly(2-isopropyl-2-oxazoline) and poly(2-isopropyl-2-oxazoline)–poly[3-(2-oxazoline)propionic acid] block copolymer arms at various ways of attaching blocks to the core are synthesized by ring-opening cationic polymerization. Luminescent labels are introduced by the esterification of carboxyl groups by diazomethane derivatives. In order to obtain interpolymer complexes luminescently labeled poly(methacrylic acid) and poly(acrylic acid) are synthesized. The resulting polymers are characterized by the methods of molecular hydrodynamics and optics. Interpolymer complex formation in the aqueous solutions of the polymers is studied by polarized luminescence. It is shown that the chemical structure of the polyoxazoline fragment and the way of its addition to the core influence the structural and dynamic characteristics of the interpolymer complexes with polycarboxylic acids and their stability.

Selective separation of polyelectrolyte nanoparticles based on formation of hydrogen-bonding interpolymer complexes

Nano-spherical polyelectrolyte brushes (SPBs) have been demonstrated to be versatile objects for many high-tech applications due to their unique microenvironment and impressive stability in aqueous media, showing great prospects in industry. However, the recycling of valuable SPBs is still a big obstacle, thereby limiting their industrial applications. Here, we show a facile approach to efficiently separate SPBs from aqueous latex solution on the basis of spherical poly(acrylic acid) brushes with a polystyrene core (PS-PAA brushes). Upon addition of poly(ethylene oxide) (PEO), hydrogen-bonding interpolymer complexes consisting of PS-PAA brushes and PEO are formed at pH below 3.5, leading to selective separation of the PS-PAA brushes from aqueous media containing other nanoparticles. Near all of the brushes are separated at pH below 3.0 regardless of the ion strengths. Importantly, the brushes can be easily redispersed by simply increasing pH, showing ignorable variations of the intrinsic properties like diameter, surface charge and light transmittance. As an application example, a catalytic nanoreactor is developed by loading sliver nanoparticles (Ag NPs) in PS-PAA brushes which show neglectable deteriorations of catalysis on the model reaction even after four separation–redispersion cycles. This work provides a simple way for selective separation of SPBs, which may benefit for industrial applications of SPBs.

PH-Induced structural transitions in whey protein isolate and ultrasonically solubilized Persian gum mixture

The present work evidently reports that ultrasonic depolymerization strongly enhanced complex coacervation between Persian gum (PG) and whey protein isolate (WPI). PG was sonicated at 60 °C, operating frequency of 20 kHz and nominal power output of 800 W for various times followed by mixing with WPI. Acid-induced interaction between the two biopolymers was studied by turbidity, light scattering, zeta potential and viscosity measurements over a wide pH range. Sonication of intact PG (IPG) for 10 min considerably reduced the molecular weight from 4.12 × 106 to 0.76 × 106 g/mol. Besides, ultrasonic fragmentation of water insoluble fraction of PG drove protein containing chains into the soluble phase. Sonicated PG (SPG) was shown to be more flexible with higher number of carboxyl groups available for electrostatic interaction with WPI, such that the complete neutralization did not occur even at protein to polysaccharide ratio of 50: 1. Additionally, scattered light intensity and viscosity measurements revealed two maxima in the pH ranges of 4.4–4.85 and 3.27–4.0, being highly intense for the gum sonicated for 10 min and longer. Considering the pH-behavior of WPI components, the former peak was related to interpolymer complex formation between β-lactoglobulin and long chain fraction of SPG, while the latter was attributed to intrapolymer association of α-lactalbumin with the short chain oligosaccharides arising from ultrasonic degradation of PG.

Effect of interpolymer complex formation between chondroitin sulfate and chitosan-gelatin hydrogel on physico-chemical and rheological properties

The present study focuses on the fabrication of three-dimensional (3D) natural polymeric hydrogel containing chitosan (C), gelatin (GE) and chondroitin sulfate A (CS) to surpass the drawbacks of chitosan-gelatin (C-GE) hydrogel. Hydrogels were prepared using dual gelling agents in the form of β-glycerol phosphate (β-GP) and sodium hydrogen carbonate (SHC) and failed to gel in the absence of either gelling agent. All the hydrogels showed the ability to self-heal when broken into two parts. The addition of CS resulted in the formation of elastic hydrogels during the entire range of applied shear strain (0.001–100 %) compared to hydrogel without CS. CS containing hydrogels resulted in 25–41 % bovine serum albumin in vitro release compared to 77 % in hydrogel without CS at the end of 16 days. The addition of VEGF165 to hydrogel improved cell proliferation drastically in C-GE hydrogel. C-GE-CS hydrogels exhibited better cell growth compared to C-GE hydrogel with or without the addition of VEGF165.

Bioplatform Fabrication Approaches Affecting Chitosan-Based Interpolymer Complex Properties and Performance as Wound Dressings.

Chitosan can form interpolymer complexes (IPCs) with anionic polymers to form biomedical platforms (BMPs) for wound dressing/healing applications. This has resulted in its application in various BMPs such as gauze, nano/microparticles, hydrogels, scaffolds, and films. Notably, wound healing has been highlighted as a noteworthy application due to the remarkable physical, chemical, and mechanical properties enabled though the interaction of these polyelectrolytes. The interaction of chitosan and anionic polymers can improve the properties and performance of BMPs. To this end, the approaches employed in fabricating wound dressings was evaluated for their effect on the property–performance factors contributing to BMP suitability in wound dressing. The use of chitosan in wound dressing applications has had much attention due to its compatible biological properties. Recent advancement includes the control of the degree of crosslinking and incorporation of bioactives in an attempt to enhance the physicochemical and physicomechanical properties of wound dressing BMPs. A critical issue with polyelectrolyte-based BMPs is that their effective translation to wound dressing platforms has yet to be realised due to the unmet challenges faced when mimicking the complex and dynamic wound environment. Novel BMPs stemming from the IPCs of chitosan are discussed in this review to offer new insight into the tailoring of physical, chemical, and mechanical properties via fabrication approaches to develop effective wound dressing candidates. These BMPs may pave the way to new therapeutic developments for improved patient outcomes.

Complexes of Amphiphilic Molecular Brushes with a Polyimide Backbone with Poly-N-Vinylamides in Selective Solvents

The interaction of a molecular brush consisting of a polyimide backbone and luminescence-labeled poly(methacrylic acid) side chains with poly-N-vinylamides (poly-N-vinylpyrrolidone and poly-N-vinylcaprolactam) with different molecular weights is studied via polarized luminescence under stationary excitation in organic solvents with different thermodynamic qualities in relation to the chain blocks of the polymers, namely, selective (methanol) and common (dimethylformamide). The decrease in the mobility of the grafted poly(methacrylic acid) chains with the growth in the molecular weight of poly-N-vinylamide observed in both selective and common solvents gives evidence of the transition from a “loose” structure to a more compact structure of the interpolymer complex. It is shown on the basis of the analysis of the nanosecond relaxation times characterizing the mobility of the sections of the grafted poly(methacrylic acid) chains and reflecting the change in the intra- and intermolecular interactions that the formation of interpolymer complexes in dimethylformamide leads to a looser structure.

New Family of Water-Soluble Sulfo-Fluoro Polyphosphazenes and Their Assembly within Hemocompatible Nanocoatings.

In this work, novel sulfo-fluoro polyphosphazenes (PPzs) were synthesized via macromolecular substitution of polydichlorophosphazene utilizing "non-covalent protection" methodology by converting acid functionalities into hydrophobic alkylammonium salts. Resulting PPzs showed excellent solubility in aqueous solutions over a broad pH range and contained ∼25% sulfo- groups and 20% either trifluoroethoxy- (FESP) or trifluoromethylphenoxy- (FPSP) side groups, as determined by NMR spectroscopy. Their polyelectrolyte behavior was evaluated by binding with an oppositely charged polyion, branched polyethylenimine (PEI), which resulted in the formation of interpolymer complexes as shown by dynamic light scattering (DLS). Contrary to a sulfonated, nonfluorinated PPz homopolymer (SP), fluorinated macromolecules effectively bound human serum albumin (HSA) as revealed by dynamic light scattering and asymmetric flow field flow fractionation (AF4) studies. Moreover, FESP and FPSP both displayed low hemolytic activity as evaluated in solution using porcine red blood cells. Using the layer-by-layer (LbL) technique, FESP and FPSP were assembled into nanocoatings with PEI. Both fluorinated and nonfluorinated sulfo PPzs showed linear growth with PEI because of strong ionic pairing between sulfo and amino groups. However, films of fluorinated PPzs displayed higher hydrophobicity, lower swelling, and improved stability in high ionic strength environment when compared to coatings formed by a sulfonated, nonfluorinated SP, or a carbon-chain polymer poly(styrene sulfonic acid). Hemocompatibility of FESP and FPSP nanofilms was demonstrated in vitro using whole rabbit blood hemolysis tests, which showed less than 1% hemolysis. Altogether, the present study introduces a new class of hemocompatible, sulfo-fluoropolymers that shows promise for life science applications.

PH Behavior of Polymer Complexes between Poly(carboxylic acids) and Poly(acrylamide derivatives) Using a Fluorescence Label Technique.

In order to clarify the local environment during interpolymer complex formation between poly(carboxylic acids) and poly(acrylamide derivatives) with different N-substitutions, a fluorescence label technique was used. 3-(2-propenyl)-9-(4-N,N-dimethylaminophenyl) phenanthrene (VDP) was used as an intramolecular fluorescence probe. All polymers were synthesized by free radical polymerization. Interpolymer complexation was monitored by charge transfer emission from the VDP unit. Both of the poly(carboxylic acids) formed interpolymer complexes with poly(N,N-dimethylacrylamide) (polyDMAM). The micro-environments around the VDP unit in the acidic pH region for the poly(methacrylic acid) (polyMAAc) and polyDMAM mixed systems were more hydrophobic than those of the poly(acrylic acid) (polyAAc) and polyDMAM mixed systems, as the α-methyl group of the MAAc unit contributed to hydrophobicity around the polymer chain during hydrogen bond formation. This suggests that, when the poly(carboxylic acids) and poly(acrylamide derivatives) were mixed, with a subsequent decrease in the solution pH, a hydrogen bond was partially formed, following which the hydrophobicity of the micro-environment around the polymer chains was changed, resulting in the formation of interpolymer complexes. Moreover, the electron-donating ability of the carbonyl group in the poly(acrylamide derivatives) had an effect on complexation with poly(carboxylic acids).

Micellization of poly(2-vinylpyrridine)-b-poly(cyclohexyl methacrylate) (P2VP-b-PCHMA) block copolymers and their interpolymer complex formation in non-aqueous medium

HypothesisThe interpolymer complex formation between poly(vinylpyridine)-based polymers with poly(acrylic acid) (PAA), in aqueous or organic medium, is driven by the hydrogen-bonding complexation. Well-defined nanostructures, with specific practical applications, may be obtained by taking advantage of such non-covalent interactions. ExperimentsPoly(2-vinylpyridine)-b-poly(cyclohexyl methacrylate) (P2VP-b-PCHMA) and poly(2-vinylpyridine)-b-poly(t-butyl methacrylate)-b-poly(cyclohexyl methacrylate) (P2VP-b-PtBuMA-b-PCHMA) copolymers were synthesized by sequential anionic polymerization. Their micellar characteristics were examined as a function of their molecular characteristics in methylcyclohexane and toluene respectively, as cycloaliphatic and aromatic solvents for the selective solubilization of the PCHMA sequence. The size of interpolymer complexes was determined by DLS, in 1,4 dioxane, and their structural composition was characterized by 1H NMR. FindingsThe scaling relationship between the molecular composition and the micellar characteristics, such as particle size and aggregation number, could be established for the PCHMA-based copolymers in methylcyclohexane. It was further demonstrated that controlled micellization in 1,4 dioxane, as a non-selective organic solvent, could be achieved by hydrogen bond type interpolymer complex formation between P2VP-b-PCHMA and PAA-b-PCHMA under stoichiometric P2VP/PAA conditions. Finally, the size of the PCHMA-b-PAA/P2VP block copolymer/homopolymer complexes as well as of the PCHMA-b-PAA/PCHMA-b-P2VP block copolymer/block copolymer complexes was correlated with the molecular characteristics of the copolymers.

Dexamethasone-Loaded Chitosan Beads Coated with a pH-Dependent Interpolymer Complex for Colon-Specific Drug Delivery

Chitosan (CS) microparticles loaded with dexamethasone were prepared by spray drying, followed by coating with a pH-dependent interpolymer complex based on poly(acrylic acid)/poly(vinyl pyrrolidone) using an water-in-oil emulsion technique. The aim of this research was to evaluate the influence of PAA/PVP coating on the release of dexamethasone from loaded chitosan microparticles, in simulated gastric fluid (SGF, pH=1.2) and simulated intestinal fluid (SIF, pH=6.8). The release of dexamethasone from uncoated loaded CS microparticles was similar in both fluids, and almost complete release of the drug was achieved in 5 hours. In the coated loaded CS microparticles, the release of dexamethasone in SGF was reduced considerably, very close to zero, due to the interpolymer complex formation at low pH, demonstrating that this system applied as pH-dependent coating has a potential as a site-specific delivery system.

Exploiting the electrical conductivity of poly-acid doped polyaniline membranes with enhanced durability for organic solvent nanofiltration

We have developed stable organic solvent nanofiltration (OSN) membranes that are electrically conductive. These membranes overcome key issues with current tuneable membranes: molecular weight cut off (MWCO) limited to the UF-range and lack of filtration stability. Polyaniline (PANI) was in-situ doped by poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) using chemical oxidative polymerization that leads to formation of interpolymer complex. The PANI-PAMPSA membranes were prepared by phase inversion method and the pore sizes were shrunk by annealing the membranes at temperatures lower than the crosslinking temperature. The membranes were systematically evaluated using visual and chemical analysis and in-filtration experiments. The developed membranes were solvent stable, reusable, had a denser structure and lower MWCO and there was no thermal crosslinking as seen by IR. The solvent permeance obtained were: 0.46, 0.60 and 0.74 Lm−2h−1bar−1 for acetone, 2-propanol and methanol respectively, with MWCO below 300 Da and 266 Da for methanol. For the tuneability investigation, when applying an electrical potential (20 V) in a custom-made cross-flow membrane cell, an increase in MWCO and permeance (10.4% and 55.6%, respectively) was observed. These results show that this simple in-situ doping method with heat treatment can produce promising and stable PANI membranes, for OSN processes in different solvents, with the distinctive feature of in-situ performance control by applying external electrical potential.

Interpolymer complexes of poly(sulfonic acid)s and poly(ethylene oxide): an unexpected association.

The formation of novel interpolymer complexes (IPCs) between poly(sulfonic acid)s and poly(ethylene oxide) (PEO) is reported. The complexes were precipitated from polymer mixtures in aqueous solution and deposited on surfaces as layer-by-layer films. Based on evidence from infrared spectroscopy, the interpolymer association in poly(sulfonic acid)/PEO IPCs is ascribed to hydrogen bonding between the sulfonic acid and the ether in PEO. This interaction is not anticipated because sulfonic acids are fully dissociated in aqueous solutions due to their strong acidity. Theoretical calculations suggest that the unexpected association of PEO and poly(sulfonic acid)s results from the formation of very strong sulfonic-acid/ether hydrogen bonds, which increase the apparent pKas of the poly(sulfonic acid)s and, therefore, decrease the net charge of these polymers. It is shown that while poly(styrene sulfonic acid) (PSSA) and Nafion form IPCs with PEO, poly(vinyl sulfonic acid) (PVSA) does not. This result is explained in terms of the hydrodrophobic nature of PSSA and Nafion, which stabilizes their IPCs, and the fact that hydrogen bonds in PSSA/PEO IPCs are predicted to be stronger than in PVSA/PEO IPCs.

Structural Organization of Interpolymer Complexes Formed by Poly(N-vinylamides) and Poly(methacrylic acid) Chains Regularly Grafted to Polyimide in Aqueous Solutions

The formation and structural organization of interpolymer complexes formed by poly(methacrylic acid) chains regularly grafted to polyimide (molecular brushes) and macromolecules of poly(N-vinylamides) with different molecular masses are studied by polarized luminescence. The luminescent label of the anthracene structure is covalently bound to poly(methacrylic acid) chains in a brush. It is shown that in aqueous solutions the complexes under study are stabilized by hydrogen bonds formed between proton donor and proton acceptor groups of interacting chains. The formation of these complexes depends not only on the nature of poly(N-vinylamide) but also especially on its molecular mass. An increase in the molecular mass of polyamide is followed by the formation of a more compact less hydrated structure, as proved by an increase in the time of nanosecond relaxation and enhanced binding of the diphilic organic ion. The hindrance of poly(methacrylic acid) grafted chains complexed with polyvinylamide is lower than that of corresponding linear chains. This can be explained by a higher imperfection of the formed double-stranded structures. The ionization of carboxyl groups leads to the dissociation of complexes. The pH range corresponding to the highest degree of binding of acridine orange by poly(methacrylic acid) grafted chains is broader than that corresponding to the highest degree of dye binding by the linear polyacid.

Flexible electro-responsive in-situ polymer acid doped polyaniline membranes for permeation enhancement and membrane fouling removal

This study investigates the performance of a new electrically tuneable polyaniline (PANI) membrane, and shows that this synthesis method has the potential to address key challenges of small-acid doped PANI membranes, including: acid dopants leaching out during filtration and low mechanical strength. The novel in-situ polymerisation used poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), as polymer acid template leads to the formation of inter-polymer complexes of PANI and polymer acid. The developed membranes were comprehensibly evaluated through visual, chemical, mechanical and filtration studies and compared to small-acid doped membranes (PANI-HCl membranes). The PANI-PAMPSA membranes were smooth, acid leach resistant, had higher tensile strength and showed conductivity three magnitudes higher compared to PANI membrane with post cast doping. The developed membrane showed in-filtration performance stability, electrical tuneability (in-situ control of flux and rejection) and fouling removal characteristics under applied electrical potential. Data obtained by SEM, IR spectroscopy, electrical analysis and cross-flow filtration confirm these results. The overall results showed that the proposed membrane fabrication procedure resulted in a significant improvement in performance across a range of critical parameters, including conductivity, stability, flexibility, permeance and fouling removal with additional advantage of being electrically tuneable.