Formation Of Mixed Complexes Research Articles

Chemical solutions for restoring scaling-induced injectivity impairment in offshore produced water re-injection

Produced water re-injection (PWRI) is a promising and sustainable strategy to manage substantial quantities of produced water for subsurface energy production systems. This approach offers an alternative to the environmentally harmful practice of marine disposal. Nonetheless, produced water re-injection may lead to considerable reductions in the injectivity. The injectivity loss can be attributed to several factors, including inorganic scaling, which can obstruct the flow pathway through porous media near the wellbore as well as subsurface facilities (e.g., tubing). Scaling can also contribute to the formation of mixed organic-inorganic schmoo-like complexes. Iron-containing (FexSy, FexOy-FexOyHz), carbonate-, and sulfate-based scales (e.g., BaSO4, SrSO4, and CaCO3) are the primary precipitates that have disruptive effects during PWRI scheme, especially in reservoirs suffering from microbial souring activities. In this work, we first screened the mineral scales that may form under the relevant re-injection conditions using the composition of produced water and seawater samples from the Danish North Sea. Subsequently, we assessed the efficiency of a commercial scale inhibitor against the scaling of targeted mineral phases through a series of batch experiments, followed by the development of a model to simulate its inhibitory performance. To reduce the precipitation or deposition of different minerals in water injection applications, we evaluated the combined effect of adding other chemicals (i.e., an acid, an oxidizer, and a chelating agent) to the injection water along with the scale inhibitor. To do this, we described the relevant mineral-aqueous interactions (dissolution, precipitation, and solution complexation) in PHREEQC. This predictive model represents an alternative to time- and resource-intensive experiments and may aid in achieving optimized chemical recipes required to mitigate mineral scaling in water injection systems under various physiochemical conditions. This work can contribute to the development of more sustainable and efficient strategies for managing produced water, ultimately helping to reduce the environmental impacts of hydrocarbon production.

Structural Characterization of Toxicologically Relevant Cd2+-L-Cysteine Complexes.

The exposure of humans to Cd exerts adverse human health effects at low chronic exposure doses, but the underlying biomolecular mechanisms are incompletely understood. To gain insight into the toxicologically relevant chemistry of Cd2+ in the bloodstream, we employed an anion-exchange HPLC coupled to a flame atomic absorption spectrometer (FAAS) using a mobile phase of 100 mM NaCl with 5 mM Tris-buffer (pH 7.4) to resemble protein-free blood plasma. The injection of Cd2+ onto this HPLC-FAAS system was associated with the elution of a Cd peak that corresponded to [CdCl3]-/[CdCl4]2- complexes. The addition of 0.1-10 mM L-cysteine (Cys) to the mobile phase significantly affected the retention behavior of Cd2+, which was rationalized by the on-column formation of mixed CdCysxCly complexes. From a toxicological point of view, the results obtained with 0.1 and 0.2 mM Cys were the most relevant because they resembled plasma concentrations. The corresponding Cd-containing (~30 μM) fractions were analyzed by X-ray absorption spectroscopy and revealed an increased sulfur coordination to Cd2+ when the Cys concentration was increased from 0.1 to 0.2 mM. The putative formation of these toxicologically relevant Cd species in blood plasma was implicated in the Cd uptake into target organs and underscores the notion that a better understanding of the metabolism of Cd in the bloodstream is critical to causally link human exposure with organ-based toxicological effects.

Structural Characterization and Antimicrobial Studies of Some New Mixed Ligand Complexes of Lomefloxacin and 3‐(Bromoacetyl)coumarin with Some Metals

AbstractThe interaction of Mn(II) (1), Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), and Zn(II) (6) with lomefloxacin (LFX) in the existence of 3‐(bromoacetyl)coumarin (BAC) and NaOH in a 1 : 1 : 1 : 1 molar ratio resulted in the formation of unique mixed ligand metal complexes. The ability of two ligands to chelate metal ions was investigated by elemental analysis, molar conductance, effective magnetic moments FT‐IR, ultraviolet‐visible (UV‐Vis), 1H NMR spectra and thermogravimetric analyses (TG‐DTG). FT‐IR spectra of the complexes suggest that LFX reacted with metal ions as bi‐dentate through pyridone oxygen and carboxylate oxygen. BAC also interacts as bi‐dentate through oxygen of α,β‐unsaturated ketone and oxygen of lactone carbonyl of coumarin. These chelates are electrolytes, according to conductivity experiments, with a 1 : 1 ratio for Mn(II), Fe(II), and Zn(II) and a 1 : 2 ratio for Co(II), Ni(II), and Cu(II). Electronic and magnetic data revealed an octahedral shape for all compounds. The thermodynamic parameters of thermal breakdown processes such as Ea, ΔH*, ΔS* and ΔG* were determined from TG and DTG curves using Coats‐Redfern (CR) and Horowitz‐Metzeger (HM) techniques for LFX, BAC and their metal complexes. The structural geometry of the complexes is confirmed by molecular modeling studies. The findings show that the complexes are soft with regard to ligands, with values ranging from 0.058 eV for Fe(II) complex to 0.090 eV for Zn(II) complex and 11.11 to 17.24 eV for LFX and BAC, respectively, and 0.121, 8.26 eV and 0.111, 9.009 eV for LFX and BAC. The ligands and their complexes were tested in vitro for antibacterial activity against a variety of bacterial and fungal strains, and the results revealed that the complexes had significantly higher potency than the parent drug.

Structure, dynamics and ionic conductivities of ternary ionic liquid/lithium salt/DMSO mixtures

In this paper we report classical Molecular Dynamics and ab initio Density Functional Theory simulations of the structure and single particle dynamics of ternary mixtures of a protic (ethylammonium nitrate, EAN) and an aprotic (1-Ethyl-3-methylimidazolium tetrafluoroborate, EMIMBF4) ionic liquid, lithium salts with common anion and a molecular cosolvent, dimethyl sulfoxide (DMSO). The coordination numbers and electrical conductivities of the different mixtures have been calculated throughout the whole concentration range, and the differences between mixtures with the protic and aprotic ionic liquids were analyzed. In both cases, the evolution of the electrical conductivity is seen to correlate well with the formation of mixed tetrahedral solvation complexes of lithium cations with ionic liquid anions and cosolvent molecules. The differences in the solvation and charge transport mechanisms in hydrogen bonded mixtures and those based in the aprotic ionic liquid are analyzed. Our conclusions indicate that the major feature behind the electrical conductivity of the ternary mixtures is the composition of the solvation shell of the metal cations in the mixtures and the rate at which anions in it are replaced by DMSO molecules.

Bimetallics in a Nutshell: Complexes Supported by Chelating Naphthyridine-Based Ligands.

Bimetallic motifs are a structural feature common to some of the most effective and synthetically useful catalysts known, including in the active sites of many metalloenzymes and on the surfaces of industrially relevant heterogeneous materials. However, the complexity of these systems often hampers detailed studies of their fundamental properties. To glean valuable mechanistic insight into how these catalysts function, this research group has prepared a family of dinucleating 1,8-naphthyridine ligands that bind two first-row transition metals in close proximity, originally designed to help mimic the proposed active site of metal oxide surfaces. Of the various bimetallic combinations examined, dicopper(I) is particularly versatile, as neutral bridging ligands adopt a variety of different binding modes depending on the configuration of frontier orbitals available to interact with the Cu centers. Organodicopper complexes are readily accessible, either through the traditional route of salt metathesis or via the activation of tetraarylborate anions through aryl group abstraction by a dicopper(I) unit. The resulting bridging aryl complexes engage in C-H bond activations, notably with terminal alkynes to afford bridging alkynyl species. The μ-hydrocarbyl complexes are surprisingly tolerant of water and elevated temperatures. This stability was leveraged to isolate a species that typically represents a fleeting intermediate in Cu-catalyzed azide-alkyne coupling (CuAAC); reaction of a bridging alkynyl complex with an organic azide afforded the first example of a well-defined, symmetrically bridged dicopper triazolide. This complex was shown to be an intermediate during CuAAC, providing support for a proposed bimetallic mechanism. These platforms are not limited to formally low oxidation states; chemical oxidation of the hydrocarbyl complexes cleanly results in formation of mixed valence CuICuII complexes with varying degrees of distortion in both the bridging moiety and the dicopper core. Higher oxidation states, e.g., dicopper(II), are easily accessed via oxidation of a dicopper(I) compound with air to give a CuII2(μ-OH)2 complex. Reduction of this compound with silanes resulted in the unexpected formation of pentametallic copper(I) dihydride clusters or trimetallic monohydride complexes, depending on the nature of the silane. Finally, development of an unsymmetrical naphthyridine ligand with mixed donor side-arms enables selective synthesis of an isostructural series of six heterobimetallic complexes, demonstrating the power of ligand design in the preparation of heterometallic assemblies.

Nature as Resource. Thermodynamic characterization of natural and synthetic polymers and their sequestering ability towards some bivalent metal cations

The aim of this paper is to enhance the knowledge on the behaviour and thermodynamic properties of natural and synthetic biopolymers in aqueous solutions. The acid-base properties of Carrageenan (Car), Xanthan gum (XG), Hydroxyethyl cellulose (HEC), Carboxymethyl cellulose (CMC), Acusol 445™ (Sol), Monopropylene glycol (MPG) and Polyethylene glycol (PEG) have been studied by potentiometric technique in NaNO3(aq), at I = 0.15 mol dm−3 and T = 298.15 K. In some cases, the protonation constants have been determined at different ionic strengths, and the dependence on ionic strength has been modelled by a Debye-Hückel type equation. The binding ability of the different polymers has been investigated towards Ca2+, Zn2+ and Sn2+ and, different speciation models have been obtained. For Acusol 445™, the weak interactions with Na+ and K+ have been determined. The effect on the complexing ability of a secondary inorganic ligand, the fluoride, has been evaluated on Carboxymethyl cellulose and Acusol systems; the formation of ternary mixed complexes with a significant increasing stability with respect the binary species has been obtained.The sequestering ability of the polymers towards the metal cations has been evaluated by means the empirical parameter pL0.5.

Redox Interactions of Vitamin C and Iron: Inhibition of the Pro-Oxidant Activity by Deferiprone.

Ascorbic acid (AscH2) is one of the most important vitamins found in the human diet, with many biological functions including antioxidant, chelating, and coenzyme activities. Ascorbic acid is also widely used in medical practice especially for increasing iron absorption and as an adjuvant therapeutic in iron chelation therapy, but its mode of action and implications in iron metabolism and toxicity are not yet clear. In this study, we used UV–Vis spectrophotometry, NMR spectroscopy, and EPR spin trapping spectroscopy to investigate the antioxidant/pro-oxidant effects of ascorbic acid in reactions involving iron and the iron chelator deferiprone (L1). The experiments were carried out in a weak acidic (pH from 3 to 5) and neutral (pH 7.4) medium. Ascorbic acid exhibits predominantly pro-oxidant activity by reducing Fe3+ to Fe2+, followed by the formation of dehydroascorbic acid. As a result, ascorbic acid accelerates the redox cycle Fe3+ ↔ Fe2+ in the Fenton reaction, which leads to a significant increase in the yield of toxic hydroxyl radicals. The analysis of the experimental data suggests that despite a much lower stability constant of the iron–ascorbate complex compared to the FeL13 complex, ascorbic acid at high concentrations is able to substitute L1 in the FeL13 chelate complex resulting in the formation of mixed L12AscFe complex. This mixed chelate complex is redox stable at neutral pH = 7.4, but decomposes at pH = 4–5 during several minutes at sub-millimolar concentrations of ascorbic acid. The proposed mechanisms play a significant role in understanding the mechanism of action, pharmacological, therapeutic, and toxic effects of the interaction of ascorbic acid, iron, and L1.

Thermodynamics of Mixed Ligand Complex Formation of Copper(II) and Nickel Ions with Glycine and Histidine in Solution

Mixed ligand complexes of copper(II) and nickel(II) with glycine (Gly) and histidine (His) have been studied in aqueous solution using calorimetric, potentiometric and spectrophotometric data at 298.15 K and the ionic strength of I = 0.5 mol·L–1 (KNO3). The thermodynamic parameters of formation of various mixed complexes have been determined. The probable coordination modes of amino acid residues in mixed ligand complexes is discussed.

ПОДВИЖНЫЙ ОБРАЗ ЖИЗНИ И ОБЩЕСТВО: СРУБНО-АЛАКУЛЬСКИЙ ФЕНОМЕН ЭПОХИ БРОНЗЫ ЮЖНОГО ЗАУРАЛЬЯ

The study discusses the influence of mobile lifestyle and migrations on social groups in the Bronze Age, first of all, age and gender groups. The article considers the sites of the Srubnaya-Alakul contact zone in the Southern Trans-Urals. In total, 11 burial grounds (148 graves and 165 individuals) have been analyzed. The study has demonstrated that the formation of mixed cultural complexes definitely reflects the changes in the social sphere too. The contact area population treated the dead women more likely in the Alakul manner than in the Srubnaya rite. On the contrary, children were buried according to the Srubnaya rite, presumably with only pottery as grave goods. Males were also buried without any grave goods, except for vessels that corresponded equally to both Alakul and Srubnaya traditions. It is difficult to reconstruct the mechanism of transferring of cultural norms from archaeological source, but it seems that there were marriages between different in their origin groups of the population, and, as a result, the Alakul traditions were gradually eroded, and the new generation was brought up in the framework of the Srubnaya cultural stereotypes. Judging by the funeral data, the Alakul tradition related to the burial of women with jewelry as grave goods turned out to be the most stable rule.

An 8-hydroxyquinoline-proline hybrid with multidrug resistance reversal activity and the solution chemistry of its half-sandwich organometallic Ru and Rh complexes.

Herein the design and synthesis of a new 8-hydroxyquinoline derivative, (S)-5-chloro-7-((proline-1-yl)methyl)8-hydroxyquinoline (HQCl-Pro), with good water solubility and multidrug resistance reversal activity are reported. In this work the proton dissociation processes of HQCl-Pro and its complex formation with [Rh(η5-C5Me5)(H2O)3]2+, [Ru(η6-p-cymene)(H2O)3]2+ and [Ru(η6-toluene)(H2O)3]2+ were investigated by the combined use of pH-potentiometry, UV-visible spectrometry and 1H NMR spectroscopy. Our results revealed the prominent solution stability of the complexes in all cases. The lipophilicity of the complexes increased with the chloride ion concentration, and the complexes showed moderate log D values (-0.8 to +0.4) at pH 7.4 at all tested Cl- concentrations. The formation of mixed hydroxido complexes from the aqua complexes was characterized by relatively high pKa values (8.45-9.62 in chloride-free medium). Complexation processes are much slower with the Ru(η6-arene) triaqua cations than with [Rh(η5-C5Me5)(H2O)3]2+. Both the pKa values and H2O/Cl- exchange constants of the Ru-complexes are lower by 0.5-1.0 orders of magnitude than those of the Rh analogue. Arene loss (p-cymene and toluene) and oxidation were found in the case of Ru-complexes when an excess of HQCl-Pro and aromatic (N,N) bidentate ligands was added. The cytotoxicity and antiproliferative effect of HQCl-Pro and its complexes were assayed in vitro. In contrast to the structurally familiar 8-hydroxyquinoline, HQCl-Pro and its Rh(η5-C5Me5) complex were somewhat more effective against drug resistant Colo 320 adenocarcinoma human cells compared to the drug sensitive Colo 205 cells. The Ru- and Rh-complexes showed a similar metal uptake level after 4 h, while a longer incubation time resulted in higher cellular Rh concentration.

BMPR2 acts as agatekeeper to protect endothelial cells from increased TGFβresponses and altered cell mechanics.

Balanced transforming growth factor-beta (TGFβ)/bone morphogenetic protein (BMP)-signaling is essential for tissue formation and homeostasis. While gain in TGFβ signaling is often found in diseases, the underlying cellular mechanisms remain poorly defined. Here we show that the receptor BMP type 2 (BMPR2) serves as a central gatekeeper of this balance, highlighted by its deregulation in diseases such as pulmonary arterial hypertension (PAH). We show that BMPR2 deficiency in endothelial cells (ECs) does not abolish pan-BMP-SMAD1/5 responses but instead favors the formation of mixed-heteromeric receptor complexes comprising BMPR1/TGFβR1/TGFβR2 that enable enhanced cellular responses toward TGFβ. These include canonical TGFβ-SMAD2/3 and lateral TGFβ-SMAD1/5 signaling as well as formation of mixed SMAD complexes. Moreover, BMPR2-deficient cells express genes indicative of altered biophysical properties, including up-regulation of extracellular matrix (ECM) proteins such as fibrillin-1 (FBN1) and of integrins. As such, we identified accumulation of ectopic FBN1 fibers remodeled with fibronectin (FN) in junctions of BMPR2-deficient ECs. Ectopic FBN1 deposits were also found in proximity to contractile intimal cells in pulmonary artery lesions of BMPR2-deficient heritable PAH (HPAH) patients. In BMPR2-deficient cells, we show that ectopic FBN1 is accompanied by active β1-integrin highly abundant in integrin-linked kinase (ILK) mechano-complexes at cell junctions. Increased integrin-dependent adhesion, spreading, and actomyosin-dependent contractility facilitates the retrieval of active TGFβ from its latent fibrillin-bound depots. We propose that loss of BMPR2 favors endothelial-to-mesenchymal transition (EndMT) allowing cells of myo-fibroblastic character to create a vicious feed-forward process leading to hyperactivated TGFβ signaling. In summary, our findings highlight a crucial role for BMPR2 as a gatekeeper of endothelial homeostasis protecting cells from increased TGFβ responses and integrin-mediated mechano-transduction.

Formation of Mixed-Ligand Metal Salts in an Organic Phase During Cation-Exchange Extraction with Tetraphenylboronic Acid Salts

Significant extraction degree of calcium and yttrium chlorides with solutions of the corresponding tetraphenylborates in tributyl phosphate has been revealed, due to the formation of mixed complex compounds in the organic phase. It has been shown that lithium, calcium, and yttrium tetraphenylborates are significantly dissociated in the organic phase. The process has been studied by conductometry. Based on the obtained data, it has been suggested that the formation of mixed halide complexes is owing to the high energy of the solvated ion pairs [CaLn]2+(A−)2 and [YLm]3+(A−)3 in organic solutions, which is significantly decreased upon the exchange of large tetraphenylborate anions with small chloride anions, possibly with the formation of solvated ion pairs with a lower charge of the cationic part of the complex [CaLn−1Cl]+A− or [YLm−2Cl2]+A−

New ternary complexes of zinc ions with glycine and histidine in solution

Mixed-ligand complexes of zinc with glycine (Gly) and histidine (His) have been studied in an aqueous solution at 298.15 K and I = 0.5 (KNO3) using calorimetric and pH-metric data. The thermodynamic parameters of formation of various mixed complexes have been determined. The probable coordination modes of amino acid residues in mixed-ligand complexes have been discussed.

Synergism and Aggregation in Multi-Extractant Solvent Extraction Systems

ABSTRACT Several combinations of lipophilic extractants have been studied with the objective of investigating the synergistic behavior of metal ion extraction and its relation to reverse micelle formation. Combinations of acidic and neutral extracting reagents that have displayed synergic behavior in other studies were tested. While most of these either showed limited synergy or no correlation with water uptake under the conditions used here, two of the systems showed extraction synergy. These two extraction systems: 2-bromodecanoic acid with 2,2ʹ:6ʹ,2ʺ-terpyridine; and tributyl phosphine oxide with 2-thenoyltrifluoroacetone were modeled based on two different theoretical approaches: microemulsion-assisted extraction; or the formation of mixed complexes in the organic phase. Comparisons between the two models showed that in the case of bromodecanoic acid and terpyridine the approach of mixed complexes provided a somewhat better fit while the second system was not modeled well with either approach. Further work on the species present in the organic phase is needed to determine the role, if any, of aggregates in synergistic solvent extraction systems.

Formation of mixed Eu(III)-CO3-fulvic acid complex: Spectroscopic evidence and NICA-Donnan modeling

Humic substances impact the fate of radionuclides in the environment. The formation of mixed complexes between lanthanides(III), carbonates, and humic substances is still a matter of debate and further studies are needed. Time-resolved luminescence spectroscopy (TRLS) is used to evidence the presence of Eu(III)-CO3-SRFA ternary complexes in media representative of environmental conditions. The evolutions of the Eu(III) luminescence spectra from the 5D0 → 7F0 to the 5D0 → 7F2 transitions are showing modifications of the asymmetry ratio — area ratio of the 5D0 → 7F2 over the 5D0 → 7F1 transition — that indicates the presence of several species in addition to the EuCO3+ and Eu-SRFA complexes. The occurrence of bi-exponential decay times, with one decay time faster than the one from Eu3+, is typical of the occurrence of fulvic complex, even in the presence of carbonate. The analyses of the indirect excitation of the Eu-CO3-SRFA system are used to build complexation isotherms varying either SRFA or total carbonate concentrations in the framework of the NICA-Donnan modeling of the Eu(III)-SRFA system. In view of the restricted pH range, no strict attribution to the different possible types of sites can be done. Different complex(es) formations are considered and discussed.

Reactions of fission products from a 252Cf source with NO and mixtures of NO and CO in an inert gas

Abstract Fission products recoiling from a 252Cf spontaneous fission source were stopped in various mixtures of inert gases containing CO and NO. For the elements of the transisition metal series Mo, Tc, Ru, and Rh previous observations of pure carbonyl complexes were reproduced. However, no formation of volatile mixed nitrosyl-carbonyl complexes or pure nitrosyl complexes for these elements have been observed. Instead, efficient production of volatile nitrosyl compounds for single iodine atoms, presumably nitrosyl iodide, NOI, was detected. This observation is of interest as potential transport path for iodine in nuclear accident scenarios and as a model for radiochemistry with the recently discovered heaviest halogen tennessine (Z=117).

Achieving Atomic Dispersion of Highly Loaded Transition Metals in Small‐Pore Zeolite SSZ‐13: High‐Capacity and High‐Efficiency Low‐Temperature CO and Passive NOx Adsorbers

AbstractThe majority of harmful atmospheric CO and NOx emissions are from vehicle exhausts. Although there has been success addressing NOx emissions at temperatures above 250 °C with selective catalytic reduction technology, emissions during vehicle cold start (when the temperature is below 150 °C), are a major challenge. Herein, we show we can completely eliminate both CO and NOx emissions simultaneously under realistic exhaust flow, using a highly loaded (2 wt %) atomically dispersed palladium in the extra‐framework positions of the small‐pore chabazite material as a CO and passive NOx adsorber. Until now, atomically dispersed highly loaded (>0.3 wt %) transition‐metal/SSZ‐13 materials have not been known. We devised a general, simple, and scalable route to prepare such materials for PtII and PdII. Through spectroscopy and materials testing we show that both CO and NOx can be simultaneously completely abated with 100 % efficiency by the formation of mixed carbonyl‐nitrosyl palladium complex in chabazite micropore.

Achieving Atomic Dispersion of Highly Loaded Transition Metals in Small-Pore Zeolite SSZ-13: High-Capacity and High-Efficiency Low-Temperature CO and Passive NOx Adsorbers.

The majority of harmful atmospheric CO and NOx emissions are from vehicle exhausts. Although there has been success addressing NOx emissions at temperatures above 250 °C with selective catalytic reduction technology, emissions during vehicle cold start (when the temperature is below 150 °C), are a major challenge. Herein, we show we can completely eliminate both CO and NOx emissions simultaneously under realistic exhaust flow, using a highly loaded (2 wt %) atomically dispersed palladium in the extra-framework positions of the small-pore chabazite material as a CO and passive NOx adsorber. Until now, atomically dispersed highly loaded (>0.3 wt %) transition-metal/SSZ-13 materials have not been known. We devised a general, simple, and scalable route to prepare such materials for PtII and PdII . Through spectroscopy and materials testing we show that both CO and NOx can be simultaneously completely abated with 100 % efficiency by the formation of mixed carbonyl-nitrosyl palladium complex in chabazite micropore.

Stability constants of mixed metal complex formation by transition metal ions with diethylene triamine pentaacetic acid (DTPA)

The formation constants for mixed metal complexes MIMIIL, where L=DTPA, MI=CuII, MII=CoII,NiII, ZnII CdII have been determined. The mixed metal complex formation of diethylene triamine pentaacetic acid (DTPA) with CuII-CoII, CuII-NiII CuII-ZnII and CuII-CdII has been studies. All the studies have been carried out pH tritrimetry at temp- 350C and ionic strength I=0.1M NaNO3. The refinement of(logβ) by SCOGS computer program.

Response of block copolyelectrolyte complexes to addition of ionic surfactants

Polyelectrolyte complex formation of a long chain poly(sodium styrene sulfonate) (NaPSS) with short chain poly(vinylbenzyltrimethylammonium chloride) homopolymer (pVBTA) and block copolymers (PEG-b-pVBTA) was investigated. The effect of the PEG chain and the pVBTA block length was studied on the complex formation. Then the exchange of the complex bound pVBTA for cetyltrimethylammonium bromide (CTAB) was studied using complexes that contained excess of pVBTA segments. First we characterized the effect of ionic strength on the complex stability. Then we studied how the addition of CTAB affects the stability of the complexes with increasing ionic strength. We found that three ionic strength ranges could be distinguished. In the lowest ionic strength range, the formation of stable mixed complexes could be observed. In the intermediate ionic strength range the pVBTA polymer was mostly substituted by CTAB, leading to the aggregation and precipitation of the complexes under the investigated conditions. Finally, at the highest ionic strength the formation of equilibrium NaPSS/CTAB complexes could be hypothesized.