Anionic Copolymer Research Articles

Polyacrylamide flocculants in phase separation processes of mineral ore salt dispersions

The features of clay-saline (potassium and sodium chlorides) dispersions flocculation using polyacrylamide and its cationic and anionic copolymers are described, including the effect of flocculant concentration, solid concentration in dispersion, method of polymer dissolution in water or saline solution on the sedimentation rate and flocculation density. It is shown that polyacrylamide has the highest flocculating ability towards clay-saline dispersion, and cationic copolymers – the lowest effect. It is shown that in concentrated clay dispersions flocculation starts at lower flocculant dose rate and occurs in a narrow range of polymer concentrations. The sedimentation rate of clay in salt dispersion increases by 15–20% with the introduction of flocculant in two stages, and by 50% times – with consequent dosing of cationic and anionic flocculant. It is also stated that polymer solutions prepared using concentrated salt solutions of potassium and sodium chlorides provide a higher efficiency of clay flocculation in comparison with solutions of polymers prepared in water.

Flocculating and Hydrodynamic Properties of Aqueous-Salt Solutions of Acrylamide Polymers

Specific features of flocculation of aqueous-salt (KCl, NaCl) clay dispersions with polyacrylamide and anionic acrylamide copolymers, including the influence exerted by the procedure of polymer dissolution in water or salt solution on the sedimentation rate and density of floccules and on the hydrodynamic properties of the polymers, are described. The use of aqueous-salt solutions of flocculants enhances the flocculating effect. The most effective flocculant for aqueous-salt clay dispersions is polyacrylamide prepared in a salt solution, which is due to higher flexibility of the polymer chain. The results obtained are of practical interest in connection with the possibility of enhancing the efficiency of the flocculation of aqueous-salt clay dispersions in dressing of potassium ores.

Anionic copolymers of acrylamide and polyacrylic acid as hydroaccumulating polymeric materials

A method for hydrogels production by the formation of cross-linked binary polymer complexes is proposed. Necessary conditions for synthesis were determined, providing a high degree of swelling of hydroaccumulating polymeric materials based on anionic copolymers of acrylamide and polyacrylic acid. Chemical interaction of components of polymer complex has been proved by the methods of infrared spectroscopy and potentiometric titration. The possibility of moisture absorption control of hydrogels depending on synthesis conditions and application purpose was shown.

Halloysite nanotubes as carriers for irinotecan: Synthesis and characterization by experimental and molecular simulation methods

Halloysite, a clay mineral with spiral-shape tubular crystal morphology and biocompatibility with the human body, could be applied for the encapsulation of various bioactive molecules, serving as a controlled drug delivery nanocarrier. In this work, halloysite nanotubes have been investigated as a potential drug delivery system of irinotecan for colon cancer treatment administered by the oral route. The irinotecan-loaded halloysite nanotubes were coated with Eudragit S100 anionic copolymer in order to control and limit the drug release in the stomach pH while allowing it in the intestinal environment. The entrapment efficiency of the irinotecan in the halloysite nanotubes was very high, reaching 84.42 ± 3.10%. Transmission electron microscopy indicated that the drug molecules are located on the surface of the halloysite nanotubes and, as X-ray diffraction patterns confirmed, they were not positioned between the individual layers of halloysite nanotube. Thermogravimetric analysis indicated drug loading levels similar to that obtained spectrophotometrically and that the halloysite:polymer weight ratio in the polymer-coated samples was similar to the respective feed weight ratio (75:25). The drug release rate from the polymer-coated nanotubes was minimal (0.7% in 2 h) at stomach pH (pH 1.2) and high at intestinal pH 7.4 conditions (when the pH was increased to 7.4, drug release increased by approx. 70% in 2 h). The classical atomistic molecular simulation methods were used for the characterization of the mutual interactions in the modeled structure between the irinotecan cations and the halloysite nanotube at release pH value (pH 7.4). According to the geometry optimization results, the drug molecules (cations) remain closer to the outer part of the halloysite nanotubes. Longitudinal axes of the adjacent drug cations are positioned along the longitudinal axis of the tube and based on the calculations, these positions are energetically preferred. Based on molecular mechanics and molecular dynamics simulations, the preferred number of the drug cations loaded in a model of 5 ring-halloysite tube with a length of 25.359 Å is 6, and this number of cations is in agreement with the molar weight ratio of the components measured in real samples.

Synthesis and characterization of novel functional poly(vinyl alcohol-co-styrene sulfonic acid) copolymers

This paper first time reports the preparation of random anionic copolymers from vinyl acetate (VAc) bearing electro-donating substituent and sodium 4-vinylbenzenesulfonate (SSA) having electro-withdrawing substituent. Copolymers (PVA-co-SSA) of different composition have been successfully prepared by a simple free radical solution polymerization technique. Resulting final copolymer contained neutral hydrophilic as well as ionizable ion exchange sites. Evaluation of spectral data obtained from Fourier transform Infrared spectroscopy, Raman spectroscopy, and 1H Nuclear magnetic resonance helped in identifying and confirming the chemical structure of copolymers. Characterization of copolymers by gel permeation chromatography revealed high molecular weight with moderate polydispersity index. Analysis of thermal stability and glass transition temperature of copolymers by thermogravimetric analysis and differential scanning calorimetry were found in between corresponding homopolymers. Physicochemical properties of PVA-co-SSA can be beneficial for prospective advanced application in the niche area of smart membrane technology for energy and environment.

A saturated saltwater drilling fluid based on salt-responsive polyampholytes

Abstract Based on special antipolyelectrolyte effect of zwitterion polymer with same quantity of anionic and cationic charges, we developed two types of salt-responsive polyampholytes, one with high molecular weight and low charge density (HvL) and the other with low molecular weight and high charge density (LvH), by inverse emulsion polymerization. Molecular structure and salt-responsiveness of them were characterized by 1H-NMR and rheology measurement, respectively. HvL and LvH were evaluated in saturated-salt bentonite suspension and influences of their ratio on apparent viscosity and fluid loss were investigated as well. The results indicate that HvL is better at decreasing fluid loss while LvH is better at maintaining low viscosity. A saturated saltwater drilling fluid centering on HvL and LvH with simple formula was designed and applied. It is indicated that salt-responsive polyampholytes are fundamentally better than AM-AMPS anionic copolymer and AM-AMPS-DMDAAC amphoteric copolymer. The saturated saltwater drilling fluid has excellent thermal stability, tolerance to bentonite and shale cuttings, and certain resistance to CaCl2. Salt-responsive polyampholytes can be used in KCl-saturated drilling fluid, with universal adaptability.

Microencapsulation of Salmonella-Specific Bacteriophage Felix O1 Using Spray-Drying in a pH-Responsive Formulation and Direct Compression Tableting of Powders into a Solid Oral Dosage Form

The treatment of enteric bacterial infections using oral bacteriophage therapy can be challenging since the harsh acidic stomach environment renders phages inactive during transit through the gastrointestinal tract. Solid oral dosage forms allowing site-specific gastrointestinal delivery of high doses of phages, e.g., using a pH or enzymatic trigger, would be a game changer for the nascent industry trying to demonstrate the efficacy of phages, including engineered phages for gut microbiome modulation in expensive clinical trials. Spray-drying is a scalable, low-cost process for producing pharmaceutical agents in dry powder form. Encapsulation of a model Salmonella-specific phage (Myoviridae phage Felix O1) was carried out using the process of spray-drying, employing a commercially available Eudragit S100® pH-responsive anionic copolymer composed of methyl methacrylate-co-methacrylic acid formulated with trehalose. Formulation and processing conditions were optimised to improve the survival of phages during spray-drying, and their subsequent protection upon exposure to simulated gastric acidity was demonstrated. Addition of trehalose to the formulation was shown to protect phages from elevated temperatures and desiccation encountered during spray-drying. Direct compression of spray-dried encapsulated phages into tablets was shown to significantly improve phage protection upon exposure to simulated gastric fluid. The results reported here demonstrate the significant potential of spray-dried pH-responsive formulations for oral delivery of bacteriophages targeting gastrointestinal applications.

Impact of different synthesis methods on the dispersing effectiveness of isoprenol ether-based zwitterionic and anionic polycarboxylate (PCE) superplasticizers

A series of zwitterionic (amphoteric) and anionic copolymers containing acrylic acid (AA), α-isoprenyloxy ω-polyethyleneglycol (IPEG) macromonomer and 2-trimethylammonium ethylmethacrylate chloride (TMAEMC) was synthesized using two different synthesis methods: in the first method, all monomers were placed into the reactor and subject to a rapid (~15 min) copolymerization while in the second AA and initiator were dosed into the vessel holding macromonomer and TMAEMC. The resulting polymer-mixtures were characterized via SEC and charge titration. Their dispersing effectiveness in cement was compared with that of PCEs prepared according to a conventional industrial process.It was found that the synthesis method greatly influences properties and performance of PCEs. The simple and fast synthesis method #1 produces highly polydisperse PCEs which are as effective as those from the optimized, carefully controlled industrial production which provides a very uniform PCE copolymer. Incorporation of cationic TMAEMC to achieve zwitterionic character only improves clay tolerance of the superplasticizer.

Physiochemical properties and paclitaxel release behaviors of dual-stimuli responsive copolymer-magnetite superparamagnetic nanocomposites

Magnetically driven drug delivery systems of superparamagnetic iron oxide nanoparticles have a considerable potential as candidates to overcome the present obstacles of drug delivery in anti-tumor therapy owing to its remote controllability by external magnetic fields and other unique properties. In this work, a biodegradable anionic copolymer with side carboxylic groups named methoxy-poly (ethylene glycol)-block-poly(α-carboxyl-ε-caprolactone) was synthesized to complex iron oxide magnetic nanoparticles and load paclitaxel (PTX) to form dual-stimuli responsive copolymer-magnetite superparamagnetic nanocomposites with an elastic core and carboxylic groups on the surface in a very easy way. The physiochemical properties of these nanocomposites were measured. High PTX loading content and high saturation magnetization were obtained. Being proved to be stable at a wide pH range and low cytotoxic in vitro, these nanocomposites presented faster PTX release in vitro at pH 6.5 than at pH 7.4 and obviously reduced burst release.

Local Structure of Ca2+ Alginate Hydrogels Gelled via Competitive Ligand Exchange and Measured by Small Angle X-Ray Scattering.

Alginates, being linear anionic co-polymers of 1,4-linked residues β-d-ManA (M) and α-l-GulA (G), are widely applied as hydrogel biomaterials due to their favourable in vivo biocompatibility and convenient ionic crosslinking. The “egg-box” model is the prevailing description of the local structure of junction zones that form between the alginate chains and divalent cations, such as Ca2+, when ionic gelation occurs. In the present study we address to what extent signatures of lateral dimerization and further lateral association of junction zones also represent a valid model for the gelation of alginate using the recently reported method of competitive ligand exchange of chelated Ca2+ ions as a method for introducing gelling ions at constant pH. Small angle X-ray scattering with a q range from 0.1 to 3.3 nm−1 was employed to determine local structure in the hydrogel, using a custom-made fluid sample cell inserted in the X-ray beam. The scattering volume was intended to be localized to the contact zone between the two injected aqueous alginate solutions, and data was captured to resolve the kinetics of the structure formation at three different conditions of pH. The data show evolution of the local structure for the Ca2+ induced formation of junction zones in an alginate with 68% G residues, characterized by cross-sectional radii that could be accounted for by a two-component, broken rod like model. The evolution of the two component weight fractions apparently underpinned the connectivity, as reflected in the rheological data.

Synthesis and performance evaluation of a polymer microsphere based nanosilica as a cementing fluid loss reducer

Polymer microspheres (ZJD-220) comprising styrene, butyl acrylate (BA) and methyl methacrylate (MMA) were prepared by soap-free emulsion polymerisation, utilising 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and sodium p-styrene sulfonate (SSS) as anionic copolymer emulsifiers, and used as a novel temperature-resistant fluid loss reducer for oil well cement. The influence of the anionic copolymer emulsifier on the properties of the polymer microspheres was assessed and the fluid loss performance of cement slurries modified by ZJD-220 was evaluated. The ratio and amount of AMPS and SSS were found to have an obvious influence on the characteristics of the polymer microspheres, whose particle size distribution was uniform and monodisperse. The ZJD-220 had excellent thermal resistance and a typical core–shell structure. The fluid losses of freshwater- and salt-based cement slurries (18% sodium chloride) modified with ZJD-220 were controlled within 43 ml and 75 ml, respectively, when the mass fraction of ZJD-220 was 3·0% of the total mass of cement under an ultra-high temperature of 200°C (bottom-hole circulating temperature). Evaluation of the performance of ZJD-220 mixed into different kinds of cement systems with other additives showed that ZJD-220 has good compatibility with different cement slurry systems and additives. Cement slurry with added ZJD-220 showed excellent ability to control filter loss due to the ‘adsorption, bridge-building, film-filling and plugging’ synergistic reaction of the ZJD-220 filling gaps between cement particles and the filter cake pores.

Polyion complexes of a cationic antimicrobial peptide as a potential systemically administered antibiotic

Antimicrobial peptides (AMPs) are regarded as next-generation antibiotics to replace conventional antibiotics due to their rapid and broad-spectrum antimicrobial properties and far less sensitivity to the development of pathogen resistance. However, they are susceptible to proteolysis in vivo by endogenous or bacterial proteases as well as induce the lysis of red blood cells, which prevent their intravenous applications. In this work, polyion complex (PIC) micelles of the cationic AMP MSI-78 and the anionic copolymer methoxy poly(ethylene glycol)-b-poly(α-glutamic acid) (mPEG-b-PGlu) were prepared to develop novel antimicrobial agents for potential application in vivo. With an increase in molar ratio of mPEG-b-PGlu to MSI-78, the complexation ability of the PIC micelles increased. FITC-labeled MSI-78 showed a sustained release from the PIC micelles. More importantly, these PIC micelles greatly decreased the hemolytic toxicity of MSI-78 to human red blood cells, without influencing its antimicrobial activity. Thus, this approach could be used as a suitable in vivo delivery method of AMPs in the future.

Effect of a copolymer poly(4-styrenesufonic acid-co-maleic acid) sodium salt on aggregation behavior of surface active ionic liquid 1-tetradecyl-3-methylimidazolium bromide and structurally similar conventional surfactant tetradecyltrimethylammonium bromide in aqueous media

The complex formation of anionic copolymer poly(4-styrenesufonic acid-co-maleic acid) sodium salt (PSSA-co-MA) with surfactant tetradecyltrimethylammonium bromide (TTAB) and surface active ionic liquid (SAIL) 1-tetradecyl-3-methylimidazolium bromide ([C14mim][Br]) has been studied in aqueous media by utilizing various techniques such as tensiometry, conductometry and fluorimetry. Conductometric and tensiometric curve of all the investigated systems demonstrate four break points corresponding to four transition states. All the thermodynamic and surface properties of surfactant-polyelectrolyte systems have been determined by conductance and surface tension measurements respectively. The value of cmc decreases with increasing the concentration of polyelectrolyte for studied systems. But it has been observed that, the lowering in cmc values is more in [C14mim][Br]-PSSA-co-MA system than TTAB-PSSA-co-MA system, although the differences in cmc are not much significant. The lowering in cmc of [C14mim][Br]-PSSA-co-MA system shows that ionic attractions between cationic head group [C14mim]+ and anionic parts (SO3− and COOH), are stronger than those in TTA+ and anionic parts (SO3− and COOH). The results indicated that the [C14mim][Br]-PSSA-co-MA complexes are comparatively more surface active than TTAB-PSSA-co-MA complexes. The fluorescence probe behaviour also confirms cmc value and provides aggregation number (Nagg). Finally all the findings of [C14mim][Br] and TTAB have been compared.

Facile preparation of structured zwitterionic polymer substrate via sub-surface initiated atom transfer radical polymerization and its synergistic marine antifouling investigation

In this paper, using one-step method of sub-surface initiated atom transfer radical polymerization (SSI-ATRP), the novel polymer brushes accompanied with structured surface were prepared on the resin base. Compared with the traditional surface initiated atom transfer radical polymerization (SI-ATRP) method, either surface chemical composition or topography was obtained through SSI-ATRP synchronously. Besides, we found that the structured polymers brush interface had better stability and long-term synergistic antifouling effect under seawater medium through soaking experiment and ocean field assay for long time. While, the bio-fouling assay results indicated that their excellent antifouling performances would be hindered by salt responsiveness of 3-sulfopropyl methacrylate potassium salt (SPMA) polymer brushes. Because it could be screened by high salt (e.g. Ca2+ or Mg2+) concentration, which decreased the hydration effect and further weakened the antifouling effect. The zwitterionic polymer (sulfobetaine methacrylate, SBMA), however, still showed excellent antifouling performances under high salt concentration since it produced stabilized ionic bonds with water molecules than those created from other hydrophilic materials. Given this, the structured zwitterionic and anionic copolymer brushes were fabricated as well, which realized the ideal stability and long-term antifouling effect under marine environment, ever high salt concentration medium. This research is of great value to marine antifouling in the long run and some other relevant fields.

Gel Transistor By Chemically Tunable Hydrogels

The transport of liquid in the polymeric network of Hydrogels have been discussed for a decade because the gel membrane may use as chemical separator [1]. Here we demonstrate a system that control the flux of solvents by a combination of three types of gels of different swelling behavior as a gel transistor. Poly(dimethyl acrylamide-co-stearyl acrylate and/or Lauryl Acrylate) (PDMMAm-co-SA and/or LA)-based shape memory gels (SMGs) swelling behavior has been observed for different solvents and binary solvent mixtures. It was found that SMGs at all composition showed increased swelling when ethanol composition was increased. On the other hand, when an anionic copolymer was introduced in the DMAA network, swelling behavior was reversed in the presence of high ethanol composition. These oppositely responsive gels were tested for permeability of solvents through them and we successfully developed the gel diode [2]. The unidirectional solvent flow was achieved just like in diode. Information about the gel diode has been utilized to develop a system that simulate a transistor to more sophistically control the flow of liquid mixtures. This findings are expected to create positive impact to develop the gel membrane solvent separator, a hot topic for rectifier, calculator and separator in chemical systems. References Tanaka, Phys. Rev. Lett. 40, 820–823 (1978).Arai, M., Gong, J., Makino, M., KABIR, M.,H., Furukawa, H. SPIE Proc. 9430, 94302A-1

Synthesis and Self-Assembly of the pH-Responsive Anionic Copolymers for Enhanced Doxorubicin-Loading Capacity.

Polyelectrolyte complex micelles self-assembled from an ionic polymer and oppositely charged small molecules are a promising drug delivery system. In this study, the anionic block copolymers composed of poly(ethylene glycol), poly(ε-caprolactone), and carboxyl modified poly(ε-caprolactone), COOH-PCEC, were designed to encapsulate doxorubicin (DOX) via electrostatic and hydrophobic interactions to form spherical micelles with a particle size of 90-140 nm. The higher payload capacity of these micelles than noncharged micelles of PCL-poly(ethylene glycol)-PCL (PCEC) was achieved, and it was strongly dependent on the composition of the micelles. In vitro drug release studies showed that the release of DOX from the micelles was faster at pH 5.5 than at pH 7.4, which was mainly due to the protonation of carboxyl groups and the solubility of DOX. Studies of intracellular uptake demonstrated that the DOX-loaded micelles could be internalized effectively by HeLa cells. In vitro cytotoxicity revealed that the blank COOH-PCEC micelles had a low cytotoxicity against both L929 and HeLa cells. However, the DOX-loaded micelles inhibited the growth of HeLa cells remarkably, demonstrating their potential for use as an efficient carrier for the delivery of DOX.

Antimalarial Activity of Orally Administered Curcumin Incorporated in Eudragit®-Containing Liposomes.

Curcumin is an antimalarial compound easy to obtain and inexpensive, having shown little toxicity across a diverse population. However, the clinical use of this interesting polyphenol has been hampered by its poor oral absorption, extremely low aqueous solubility and rapid metabolism. In this study, we have used the anionic copolymer Eudragit® S100 to assemble liposomes incorporating curcumin and containing either hyaluronan (Eudragit-hyaluronan liposomes) or the water-soluble dextrin Nutriose® FM06 (Eudragit-nutriosomes). Upon oral administration of the rehydrated freeze-dried nanosystems administered at 25/75 mg curcumin·kg−1·day−1, only Eudragit-nutriosomes improved the in vivo antimalarial activity of curcumin in a dose-dependent manner, by enhancing the survival of all Plasmodium yoelii-infected mice up to 11/11 days, as compared to 6/7 days upon administration of an equal dose of the free compound. On the other hand, animals treated with curcumin incorporated in Eudragit-hyaluronan liposomes did not live longer than the controls, a result consistent with the lower stability of this formulation after reconstitution. Polymer-lipid nanovesicles hold promise for their development into systems for the oral delivery of curcumin-based antimalarial therapies.

Efficient Praziquantel Encapsulation into Polymer Microcapsules and Taste Masking Evaluation Using an Electronic Tongue

Abstract Taste masking is an important strategy for improving adherence of patients, especially children, who have to take pharmaceutical drugs with a bitter taste, as is the case of praziquantel (PZQ) used to treat schistosomiasis. In this work, a modified interfacial polymer deposition method was used to prepare polymer microcapsules and microspheres to encapsulate PZQ, where formulations were optimized to fulfill the stringent requirements for controlled drug release. In vitro release tests confirmed the suitability of the formulation with microcapsules of the anionic copolymer L30D, in which the loading of PZQ was larger than 90% in solutions that were stable at low pH but released PZQ under enteric conditions. We also show that the encapsulation was effective in terms of masking PZQ taste through the analysis with an electronic tongue.

Layer-By-Layer Self-Assembly of Polyelectrolytic Block Copolymer Worms on a Planar Substrate.

Cationic and anionic block copolymer worms are prepared by polymerization-induced self-assembly via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion copolymerization of 2-hydroxypropyl methacrylate and glycidyl methacrylate (GlyMA), using a binary mixture of a nonionic poly(ethylene oxide) macromolecular RAFT agent and either a cationic poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) or an anionic poly(potassium 3-sulfopropyl methacrylate) macromolecular RAFT agent. In each case, covalent stabilization of the worm cores was achieved via reaction of the epoxide groups on the GlyMA repeat units with 3-mercaptopropyltriethoxysilane. Aqueous electrophoresis studies indicated a pH-independent mean zeta potential of +40 mV and −39 mV for the cationic and anionic copolymer worms, respectively. These worms are expected to mimic the rigid rod behavior of water-soluble polyelectrolyte chains in the absence of added salt. The kinetics of adsorption of the cationic worms onto a planar anionic silicon wafer was examined at pH 5 and was found to be extremely fast at 1.0 w/w % copolymer concentration in the absence of added salt. Scanning electron microscopy (SEM) analysis indicated that a relatively constant worm surface coverage of 16% was achieved at 20 °C for adsorption times ranging from just 2 s up to 2 min. Furthermore, the successive layer-by-layer deposition of cationic and anionic copolymer worms onto planar surfaces was investigated using SEM, ellipsometry, and surface zeta potential measurements. These techniques confirmed that the deposition of oppositely charged worms resulted in a monotonic increase in the mean layer thickness, with a concomitant surface charge reversal occurring on addition of each new worm layer. Unexpectedly, two distinct linear regimes were observed when plotting the mean layer thickness against the total number of adsorbed worm layers, with a steeper gradient (corresponding to thicker layers) being observed after the deposition of six worm layers.

Degradation of drag reducing polymers in aqueous solutions

The performance of drag reducing polymers in turbulent flow is restricted by their mechanical degradation. This study examines how the working fluid can affect the degradation behavior of diluted drag reducing polymeric solutions. Solutions having different proportions of tap water and de-ionized water served as the working fluids. Three commercially available water soluble polymeric agents, namely, an anionic copolymer of polyacrylamide, xanthan gum, and polyethylene oxide, were then added to these solutions. All experiments had identical flow rates corresponding to turbulent conditions in a laboratory scale pipe line. Variation of pressure drop in the pipe line was then measured for 2 hours. It was found that polymer degradation is accelerated in tap water solutions compared to that in de-ionized water solutions. However, this is dependent on the specification of the polymer used, namely, the molecular weight of the polymer and the rigidity of its molecular backbone. Furthermore, a new mathematical relation has been developed to investigate degradation of the polymers over time.