Non-stoichiometric Polyelectrolyte Complexes Research Articles

Polyelectrolyte complex membranes as a selective zincate separator for secondary zinc-air battery

Zinc-air batteries (ZABs) are being extensively studied as an alternative to lithium batteries due to their high energy density and overall safety benefit. While considerable attention has been given to the development of anodes and cathodes for ZABs, the separator membrane component has received relatively little focus. The separator is supposed to play a critical role in rechargeable ZABs by allowing hydroxide ions to permeate while blocking zincate ions. In this study, we investigated for the first time the potential use of polyelectrolyte complex (PEC) membranes as separators for rechargeable ZABs. These membranes were formed by mixing cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic poly(sodium-4-styrenesulfonate) (PSS) at various molar ratios, followed by compression molding of the mixture precipitates after centrifugation. Among the different molar ratios tested, the non-stoichiometric PEC (2:1) membrane exhibited the highest ionic selectivity with a diffusion rate of 1.98 × 10−7 cm2 min−1 for Zn(OH)42−. Subsequently, the PEC membranes were integrated into homemade ZABs, and galvanostatic cycling tests were conducted. Overall, the PEC (2:1) membrane demonstrated superior separator ability for rechargeable ZABs compared to the other prepared molar ratios.

POLYELECTROLYTE COMPLEX NANOPARTICLES OF SOLUBLE LIGNIN AND CHITOSAN AS INTERFACIAL MODIFIER

A water-soluble non-stoichiometric polyelectrolyte complex (LCP) was obtained as a result of the interaction of oppositely charged kraft lignin and high molecular chitosan by mixing their dilute water solutions. The sizes of the LCP nanoparticles were characterized by a bimodal distribution at pH 6, and their values were essentially smaller than the sizes of the chitosan particles. It was found that the LCP nanoparticles were characterized by remarkably lower values of surface tension at the air-water and the water-organic liquid interface in comparison with the initial biopolymers. With decreasing pH and increasing concentration of the LCP nanoparticles in the water solution, their adsorption ability at the interfaces was enhanced. The interface tension at the water-heptane interface changed non-linearly with increasing the polyelectrolyte complex concentration that was associated with the “saturation” effect. The dependence of the ability of the LPC nanoparticles to stabilize oil-in-water emulsion on pH values of the water phase was found.

Sand/Polyethyleneimine Composites with Enhanced Sorption/Desorption Properties toward Pollutants

The direct deposition of polyethyleneimine (PEI), a weak polycation with a large content of amino groups, onto sand fractions with different sizes (F70, F100, F200, and F355), resulted in versatile core-shell sorbents for water cleaning. Herein, PEI and the weak polyanion poly(acrylic acid) (PAA) were directly precipitated as an nonstoichiometric polyelectrolyte complex ([PEI]:[PAA] = 2:1) onto a sand surface followed by cross-linking with glutaraldehyde (GA) at three molar ratios ([CHO]:[amine] = 1:10; 1:5; 1:1 = r). Non-crosslinked polyelectrolyte chains were washed out in strongly basic (pH 14) and acidic (pH 0) media. The sand/PEI-GA composites were evaluated to determine the organic shell stability using swelling experiments and X-ray photoelectron spectroscopy. The sorbed/desorbed amount of two model pollutants (copper ions and bromocresol green) in column experiments depended on the sand fraction size and cross-linking degree of the PEI shell. The maximum recorded values, after five loading/release cycles of pollutant species onto F70/PEI-GAr, F100/PEI-GAr, F200/PEI-GAr, and F355/PEI-GAr, were situated between the 0.7–5.5 mg Cu2+/mL column and 3.7–15 mg BCG/mL column. Sand/PEI-GAr composites could act as promising sorbents, low-cost and eco-friendly, which could be applied for water purification procedures.

Hydrophobic Composites Designed by a Nonwoven Cellulose-Based Material and Polymer/CaCO3 Patterns with Biomedical Applications.

Herein, we report a simple method to obtain hydrophobic surfaces by surface modification with calcium carbonate via diffusion-controlled crystallization using a cheap, versatile, and super-hydrophilic cellulose-based nonwoven material (NWM) as the substrate. To control the CaCO3 crystal growth, the ammonium carbonate diffusion method was applied in the presence of polyanions [poly(acid acrylic), poly(2-acrylamido-2-methylpropanesulfonic acid), and a copolymer which contains 55 mol % 2-acrylamido-2-methylpropanesulfonic acid and 45 mol % acrylic acid] or nonstoichiometric polyelectrolyte complexes with polycations [poly(allylamine hydrochloride) and chitosan] on a pristine NWM and on polycation-treated surfaces. The surface morphology obtained by calcite growth under surface or environmental functional groups' influence and the hydrophilic/hydrophobic character of the composite materials were followed and compared to that of the starting material. The obtained composite materials become hydrophobic, having a contact angle in the range of 110-135°. The capacity of tetracycline sorption and release by selected modified surfaces were followed and compared to the untreated NWM. Also, the biological properties were evaluated in terms of biocompatibility, antibacterial activity, and antifouling capability.

Effect of the composition stoichiometry and salt on the ammonia sensing properties of curcumin-loaded polyelectrolyte complex membranes

Nonstoichiometric polyelectrolyte complex (PEC) membranes loaded with natural colorimetric indicator 1,7-bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin, Cur) were used as visual detectors for ammonia (NH3) vapors. PEC membranes were fabricated by the co-precipitation of cationic poly(diallyldimethylammonium chloride) (PDADMAC) and anionic poly(sodium 4-styrene sulfonate) (PSS) using NaCl as a plasticizer followed by centrifugation and compression molding into 120-micron sheets. The polymer complex (PEC) was prepared using various molar ratios of PDADMAC and PSS [P+]/[P−] of [2:1], [1:1] and [1:2] which color response when exposed to ammonia vapor shifted from yellow to orange-red. The fast color change was clearly observed by naked eyes and confirmed by UV–Vis spectroscopy. The main finding of this paper is that the PDADMAC-rich membrane with a [P+]/[P−] of [2:1] displayer better NH3 sensing and that different salts used in the processing of the PEC can improve the sensitivity of the sensors by increasing the moist content in the membranes. The reversible color change to yellow was possible at ambient temperature when the ammonia vapor was removed making these sensors reusable. These Cur-PEC membranes could be used in sensing applications to monitor the release of NH3 gas from industrial sites by optical detection.

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.

Novel Antibacterial Food Packaging Based on Chitosan Loaded ZnO Nano Particles Prepared by Green Synthesis from Nettle Leaf Extract

New nonstoichiometric polyelectrolyte complex was prepared based on chitosan (CS) and Carboxymethyl cellulose (CMC) and the addition of ZnO nano particles prepared by green synthesis from Nettle leaf extract for increasing the antibacterial properties. The composites were prepared in different mass ratios and the physicochemical properties of the complexes were investigated by means of scanning electron microscopy, atomic force microscopy, FTIR analyzer, water absorption test, UV–Vis analyzer and thermal analyzer. The results indicated that the slow dropwise addition of CMC to chitosan allowed elaborating either anionic or cationic particles in the size range of 35.5–69.7 nm. The water uptake and the ash percentage of the nano composites increase by increasing the amount of CMC and the transparency and the opacity of Chitosan:CMC (75:25) is the best. The highest antibacterial activity related to the synthesised composite without nano ZnO for Escherichia coli and the best result achieved in prepared nano composite and adding nano ZnO (PCC3/ZnO) in Staphylococcus aureus medium.

Effects of (complementary) Polyelectrolytes Characteristics on Composite Calcium Carbonate Microparticles Properties

This study follows the possibility to tune the thermal stability of some CaCO3/polymer composites by crystal growth from supersaturated solutions controlled by polymer structure or by using nonstoichiometric polyelectrolyte complexes (NPECs). As the ratio between the organic and inorganic parts in the composites controls the Ca2+/polymer network crosslinking density, the CaCO3/polymer weight ratio was kept constant at 50/1, varying the initial concentration of the polyanions solutions (0.05 or 0.06 wt.%), the NPECs molar ratio , n+/n- (0.2 or 0.4), or the inorganic precursors concentration (0.25 or 0.3 M). Poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylic acid) (PSA) and chondroitin-4-sulfate (CSA) were used as polyanions. Some NPEC dispersions, prepared with the same polyanions and poly(allylamine hydrochloride) (PAH), were also used for calcium carbonate crystallization. The characteristics of the prepared composites were investigated by scanning electron microscopy (SEM), flow particle image analysis (FPIA), particles charge density (CD), zeta-potential (ZP). The thermal stability of the composite particles was investigated as compared to bare CaCO3 microparticles prepared at the same initial inorganic concentrations.

Autotemplate Microcapsules of CaCO3/Pectin and Nonstoichiometric Complexes as Sustained Tetracycline Hydrochloride Delivery Carriers.

New types of composites were obtained by an autotemplate method for assembling hollow CaCO3 capsules by using pH-sensitive polymers. Five pectin samples, which differ in the methylation degree and/or amide content, and some nonstoichiometric polyelectrolyte complex dispersions, prepared with the pectin samples and poly(allylamine hydrochloride), were used to control the crystal growth. The morphology of the composites was investigated by scanning electron microscopy, and the polymorphs characteristics were investigated by FTIR spectroscopy. The presence of the polymer in the composite particles was evidenced by X-ray photoelectron spectroscopy, particle charge density, and zeta-potential. The new CaCO3/pectin hollow capsules were tested as a possible matrix for a tetracycline hydrochloride carrier. The kinetics of the drug release mechanism was followed using Higuchi and Korsmeyer-Peppas mathematical models.

Short Fibre Filler from Wood Residue for Polymeric Composite Materials

a wood residue – sawdust of the mechanical processing of aspen (Populus tremula) wood – was used to obtain a short fibre filler in the form of the modified microparticles < 250 µm for polymeric composite materials. To reduce energy input for wood size reduction and the activation of the lignocellulosic matrix for modification, low temperature acid hydrolysis of the residue under mild conditions was carried out. the effect of the pre-treatment parameters (acid concentration, hydrolysis duration, hydromodulus) on the fractional and chemical composition as well as on the zeta potential and contact angle of the obtained filler was studied. A comparison of the mechanical properties (tensile, bending) of the composites filled with initial sawdust and hydrolysed microparticles modified with a non-stoichiometric polyelectrolyte complex showed a pronounced improvement of the mechanical properties of the composites filled with modified wood microparticles.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.8752

Eco-Friendly Constituents for Making Wood-Polymer Composites

The aim of this work was to obtain eco-friendly constituents for making wood-polymer composites (WPCs) by rational utilisation of hardwood residue with its mechanical processing and purposeful chemical modification. To reduce the energy input for residue milling for obtaining a lignocellulosic filler as well as to activate its surface for the further modification, the optimal parameters of low temperature acid hydrolysis of the hardwood residue under mild conditions were found. To enhance the wetting of the lignocellulosic filler with respect to recycled polypropylene, the milled hydrolysed wood particles were modified by ammoxidation. For obtaining a lignin-containing surface tension regulator (compatibiliser) that is able to reinforce the interaction between the constituents at the interface, soda lignin was obtained via delignification of the hydrolysed hardwood residue under laboratory conditions. The developed compatibiliser represented nanoparticles of a non-stoichiometric polyelectrolyte complex, incorporating soda lignin and synthetic polyamine - polyethylenimine. By using appropriate laboratory equipment and the determined technological regime, aspen wood-recycled polypropylene composites were made and tested.

Multi-region to single region shear thinning transitions in drying PEDOT:PSS dispersions: contributions from charge density fluctuations.

PSS), in water during the drying process is explored. PSS dispersions in water can be non-stoichiometric polyelectrolyte complexes (PECs) with free polyanion (PSS) chains resulting in scrambled egg conformations. They also behave as charged colloidal particles. The behaviour of PSS dispersions as PECs and charged colloidal systems during drying is analyzed using rheology and TEM, zeta potential, conductivity, pH, dynamic light scattering (DLS) and rheo-small angle light scattering (rheo-SALS) information. The rheological behaviour is found to have significant contributions from conformational changes in the PSS PEC due to charge density fluctuations affecting the electrostatic persistence length, le. A low concentration regime with multiple shear thinning behaviour and a high concentration regime with single shear thinning behaviour were observed. The PEC behavior of PSS is further explored by charge neutralizing the dispersions with salts.

Calcium Carbonate/Polymers Microparticles Tuned by Complementary Polyelectrolytes as Complex Macromolecular Templates

This study describes the effects of mixed anionic/cationic polyelectrolytes on the crystallization of calcium carbonate in supersaturated solutions in comparison with polyanion-based CaCO3 composite structures. Two simple methods of introducing the polycation in the crystallogenesis of calcium carbonate are proposed: preformed nonstoichiometric polyelectrolyte complexes (NPECs) or in situ mixing of complementary polyelectrolytes, with a very large range of ratios between complementary polyions. For this purpose three polyanions—poly(acrylic acid) sodium salt, poly(sodium 4-styrenesulfonate) and poly(sodium vinylsulfonate)—and poly(diallyl-dimethylammonium chloride) as polycation were used. The molar ratio between complementary polyelectrolytes used in CaCO3 composite synthesis varied between 0 (just polyanions) up to 0.95 (close to the equimolar ratio between ionic charges of complementary polyelectrolytes). The polymer presence into the composite particles, as a function of polyanion structure and the preparation mode, was evidenced by energy dispersive X-ray diffraction and particle charge detection in the supernatant fraction. Scanning electron microscopy was used to provide the particles’ morphology, and Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy was used to determine the polymorph content ratio. The enhanced CaCO3/polyanion/polycation microparticles stability in ethylenediamine tetraacetic acid has been also shown compared to CaCO3/polyanion microparticles as a function of the molar ratio between complementary polyelectrolytes and the method of introducing the polycation in the crystallogenesis system.

Formation of copper nanoparticles during the reduction of Cu2+ ions in solutions and dispersions of polycation-poly(acrylic acid) interpolymer complexes in acidic media

The phase behavior of mixed acidic solutions of the high-molecular-mass cationic polyelectrolyte poly(1,2-dimethyl-5-vinylpyridinium methyl sulfate) and PAA at a PAA-to-polycation ratio of <1 base-mol/base-mol in narrow pH ranges at 6–30°C is studied. The reduction of Cu2+ ions in solutions and dispersions of interpolyelectrolyte complexes yields copper nanoparticles. It is shown that the mean-square diameters of nanoparticles formed in solutions of nonstoichiometric polyelectrolyte complexes are much smaller than those obtained in solutions of each component of the polyelectrolyte complex under the same conditions. These values decrease as the thermodynamic quality of the solvent with respect to the polymer of the pseudomatrix nonstoichiometric polyelectrolyte complex worsens. The experimental data may be explained in terms of the theoretical concept of pseudomatrix formation of a new phase in polymer solutions.

Nonstoichiometric Polyelectrolyte Complexes: Smart Nanoreactors for Alloy and Multimetallic Catalyst

Nonstoichiometric Polyelectrolyte Complexes: Smart Nanoreactors for Alloy and Multimetallic Catalyst

Nonstoichiometric Polyelectrolyte Complexes Versus Polyanions as Templates on CaCO3-Based Composite Synthesis

The characteristics of calcium carbonate microparticles formed in supersaturated aqueous solutions, in the presence of some strong/weak anionic polymers or with nonstoichiometric polyelectrolyte complexes with negative charges in excess (NPEC-n), have been investigated under different relative inorganic/polymer ratios, tuned by initial solution supersaturation and polymer concentration. For this purpose two polyanions which contain the carboxylic and sulfonic ionic groups, poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylic acid) and chondroitin-4-sulfate, were used. NPEC-n dispersions prepared with the same polyanions and chitosan as a polycation were also used as templates for calcium carbonate crystallization. Scanning electron microscopy was used to provide the particle morphologies and flow particle image analysis to evidence their mean sizes and sphericities. The polymer presence in the composite particles was evidenced by X-ray photoelectron spectroscopy, particle charge densities, and zeta p...

Relationship between intermolecular bonding, nanostructure, phase behavior, and macroscopic physical properties of pressure-sensitive adhesives based on polyelectrolyte complexes

Correlations have been established between mechanisms of molecular interaction, the energy of intermolecular bonds, nanoscopic free volume, phase state, and such macroscopic physical properties as linear and large-strain viscoelasticity, relaxation, water-absorbing capacity, and adhesive joint strength of pressure sensitive adhesives based on nonstoichiometric polyelectrolyte complexes. The polyelectrolyte complexes are formed by mixing of a polybase, copolymer of N,N-dimethylaminoethyl methacrylate with methyl methacrylate and butyl methacrylate (PDMAEMA-co-MMA/BMA), with a polyacid, copolymer of methacrylic acid and ethyl acrylate (PMAA-co-EA) in the presence of triethyl citrate (TEC) as a plasticizer. Rubber-like elasticity and pressure sensitive adhesion of the polyelectrolyte complexes on the macroscopic level have been demonstrated to be the result of specific coupling of such generally conflicting properties of polymer materials as sufficiently strong intermolecular cohesion energy with comparatively large free volume (vacant space between neighboring macromolecules) at the nanoscopic scale. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Thermo- and pH-responsive polyelectrolyte complex membranes from chitosan-g-N-isopropylacrylamide and pectin

Non-stoichiometric polyelectrolyte complex membranes between chitosan-g-N-isopropylacrylamide (PNIPAm) and pectin were prepared and subjected to a thermal treatment by which ionic bonds were converted into amide bonds. Membranes are hydrophilic, with opaque appearance, but vitreous when dry. Swollen membranes undergo a sharp shrinking process with an inflexion point at 33.1°C. Below LCST, NIPAm chains are hydrated and completely stretched. As temperature increases above LCST, NIPAm chains contract and water is expelled from the polymer matrix, giving rise to the phase transition that is associated to an endothermic peak and is fully thermoreversible. These membranes are not only sensitive to temperature, but also to the pH of the medium whose variation has no influence on LCST. Nevertheless, transition enthalpy decreases when pH increases within studied interval, showing the same trend as equilibrium swelling.

Water-soluble nonstoichiometric polyelectrolyte complexes of modified chitosan

A modified polysaccharide that, in each deacetylated unit, carries a functional secondary amino group and a quaternized amino group that provides a positive charge and solubility to the polymer throughout the pH range is prepared by the alkylation of primary amino groups of chitosan with glycidyltrimethylammonium chloride. The mixing of modified chitosan solutions with solutions of polystyrenesulfonate or polymethacrylate anions in neutral solutions gives rise to negatively charged nonstoichiometric polyelectrolyte complexes soluble and stable under physiological conditions. The effects of pH, ionic strength, the degree of polymerization, the nature of the lyophilizing polyanion, and the charge-to-charge ratio of components on the boundaries of existence of soluble complexes are ascertained. The collected experimental data may serve as a basis for designing biocompatible and biodegradable means useful for the delivery of genetic material and drugs to living cells.

Adsorption Characteristics of Stoichiometric and Nonstoichiometric Molecular Polyelectrolyte Complexes on Silicon Oxynitride Surfaces

Adsorption properties of stoichiometric and nonstoichiometric polyelectrolyte complexes (PECs) have been investigated by means of dual polarization interferometry (DPI) and X-ray photoelectron spectroscopy (XPS). Poly(sodium styrenesulfonate) (NaPSS) of molecular weight 4300 g/mol was used as polyanion, and two bottle-brush copolymers possessing different molar ratios of the cationic segment methacryloxyethyltrimethylammonium chloride (METAC) and the nonionic segment poly(ethylene oxide) methyl ether methacrylate (PEO(45)MEMA) were used as polycations. They are referred to as PEO(45)MEMA:METAC-25 and PEO(45)MEMA:METAC-50, where the last digits denote the mol % of charged main-chain segments. The time evolution of the adsorbed amount, thickness, and refractive index of the PEC layers were determined in aqueous solution using DPI. We demonstrate that cationic, uncharged, and negatively charged complexes adsorb to negatively charged silicon oxynitride and that maximum adsorption is achieved when small amounts of PSS are present in the complexes. The surface composition of the adsorbed PEC layers was estimated from XPS measurements that demonstrated very low content of NaPSS. On the basis of these data, the PEC adsorption mechanism is discussed and the competition between PSS and negative surface sites for association with the cationic polyelectrolyte is identified as a key issue.