Acid Of Different Molecular Weights Research Articles

Effectiveness of topical hyaluronic acid of different molecular weights in xerosis cutis treatment in elderly: a double-blind, randomized controlled trial.

Dry skin is a common dermatological condition that frequently affects the elderly. A contributing cause to dry skin is a reduced concentration of hyaluronic acid (HA) in both the epidermis and dermis. The effectiveness of moisturizer containing HA as a therapy for dry skin is impacted by its specific molecular weight. Low molecular weight HA (LMWHA) is believed to be more effective in replenishing skin hydration in aging skin compared to High Molecular Weight HA (HMWHA) due to its ability to penetrate the stratum corneum. However, there is a lack of clinical research supporting this claim. A double-blind, randomized controlled trial was conducted on 36 residents of a nursing home in Jakarta. The participants, aged between 60 and 80 years, had been diagnosed with dry skin. Each test subject was administered three distinct, randomized moisturizing lotions (LMWHA, HMWHA, or vehicle), to be topically applied to three separate sites on the leg. Skin capacitance (SCap), transepidermal water loss (TEWL), and specified symptom sum score (SRRC) were measured at weeks 0, 2, and 4. After four weeks of therapy, area that was treated with LMWHA showed greater SCap values compared to the area treated with HMWHA (56.37 AU vs. 52.37 AU, p = 0.004) and vehicle (56.37 AU vs. 49.01 AU, p < 0.001). All groups did not show any significant differences in TEWL and SRRC scores. No side effects were found in all groups. The application of a moisturizer containing LMWHA to the dry skin of elderly resulted in significant improvements in skin hydration compared to moisturizers containing HMWHA and vehicle. Furthermore, these moisturizers demonstrated similar safety in treating dry skin in the elderly. ClinicalTrials.gov Identifier NCT06178367, https://clinicaltrials.gov/study/NCT06178367 .

Thermosensitive Intravitreal In Situ Implant of Cefuroxime Based on Poloxamer 407 and Hyaluronic Acid.

The main method of treatment and prevention of endophthalmitis is a combination of intravitreal and topical administration of antibiotics, such as cefuroxime moxifloxacin or vancomycin. However, this method is ineffective due to the rapid elimination of the drug. This problem can be solved with the help of intravitreal in situ injection systems, which are injected with a syringe into the vitreous body and provide prolonged action of the drug at the focus of inflammation. Under the influence of temperature, the liquid drug undergoes a phase transition and turns into a gel after injection. This ensures its prolonged action. The study aimed to develop an intravitreal in situ cefuroxime delivery system for the treatment of endophthalmitis based on a thermosensitive biodegradable composition of poloxamer 407 and hyaluronic acid. A combination of poloxamer Kolliphor® P407, Kolliphor® P188, and PrincipHYAL® hyaluronic acids of different molecular weights was used as a delivery system. The potency of cefuroxime solid dispersion with polyvinylpyrrolidone-10000, polyethylene glycol-400, and polyethylene glycol-1500 in a 1:2 ratio was studied for prolonged action compared to cefuroxime substance. The experimental formulations were studied for the parameters of gelation temperature in a long-term test (4 months), pH, and release of cefuroxime using dialysis bags. To study the distribution parameter in the vitreous body, an in vitro model (1/13) was developed, which was a hollow agar sphere filled with 1% (w/v) polyacrylate gel. For the superior formulations, a HET-CAM test (chorioallantoic membrane test) was performed to determine the absence of irritant effects. According to the study results, a formulation containing a solid dispersion of cefuroxime:PEG-400 (1:2), the matrix of which contained 18% (w/v) Kolliphor® P407 poloxamer, 3% (w/v) Kolliphor® P188 poloxamer, and 0.5% (w/v) hyaluronic acid (1400-1800), was selected. This sample had an average gelation temperature of 34.6 °C, pH 6.7 ± 0.5, and a pronounced prolonged effect. Only 7.6% was released in 3 h of the experiment, whereas about 38% of cefuroxime was released in 72 h. No irritant effect on the chorioallantoic membrane was observed for any formulations studied.

Effect of the Addition of Polyacrylic Acid of Different Molecular Weights to Coagulation Bath on the Structure and Performance of Polysulfone Ultrafiltration Membranes

Membrane fouling is a serious issue in membrane technology which cannot be completely avoided but can be diminished. The perspective technique of membrane modification is the introduction of hydrophilic polymers or polyelectrolytes into the coagulation bath during membrane preparation via non-solvent-induced phase separation. The influence of polyacrylic acid (PAA) molecular weight (100,000, 250,000 and 450,000 g·mol-1) added to the aqueous coagulation bath (0.4-2.0 wt.%) on the polysulfone membrane structure, surface roughness, water contact angle and zeta potential of the selective layer, as well as the separation and antifouling performance, was systematically studied. It was found that membranes obtained via the addition of PAA with higher molecular weight feature smaller pore size and porosity, extremely high hydrophilicity and higher values of negative charge of membrane surface. It was shown that the increase in PAA concentration from 0.4 wt.% to 2.0 wt.% for all studied PAA molecular weights yielded a substantial decrease in water contact angle compared with the reference membrane (65 ± 2°) (from 27 ± 2° to 17 ± 2° for PAA with Mn = 100,000 g·mol-1; from 25 ± 2° to 16 ± 2° for PAA with Mn = 250,000 g·mol-1; and from 19 ± 2° to 10 ± 2° for PAA with Mn = 450,000 g·mol-1). An increase in PAA molecular weight from 100,000 to 450,000 g·mol-1 led to a decrease in membrane permeability, an increase in rejection and tailoring excellent antifouling performance in the ultrafiltration of humic acid solutions. The fouling recovery ratio increased from 73% for the reference membrane up to 91%, 100% and 136% for membranes modified with the addition to the coagulation bath of 1.5 wt.% of PAA with molecular weights of 100,000 g·mol-1, 250,000 g·mol-1 and 450,000 g·mol-1, respectively. Overall, the addition of PAA of different molecular weights to the coagulation bath is an efficient tool to adjust membrane separation and antifouling properties for different separation tasks.

Versatile biomimetic conductive polypyrrole films doped with hyaluronic acid of different molecular weights

Electrically conductive polypyrrole (PPy) is an intriguing biomaterial capable of efficient electrical interactions with biological systems. Especially, biomimetic PPy-based biomaterials incorporating biomolecules, such as hyaluronic acid (HA), can impart the characteristic biological interactions with living cells/tissues to the conductive biomaterials. Here we report the effects of the molecular weight (MW) of HA on PPy-based biomaterials. We utilized HA of a wide range of MW (35 × 103 Da–3 × 106 Da) as dopants during the electrochemical production of PPy/HA films and their characterization of materials and cellular interactions. With increases in the MWs of HA dopants, PPy/HA exhibited more hydrophilic, higher electrochemical activity and lower impedance. In vitro studies revealed that PPy films doped with low MW HA were supportive to cell adhesion and growth, while PPy films doped with high MW HA were resistant to cell attachment. Subcutaneous implantation of the PPy/HA films for 4 weeks revealed that all the PPy/HA films were tissue compatible. We successfully demonstrate the importance of HA dopant MWs in modulating the chemical and electrical properties of the materials and cellular responses to the materials. Such materials have potential for various biomedical applications, including as tissue engineering scaffolds and as electrodes for neural recording and neuromodulation. Statement of SignificanceHyaluronic acid (HA)-doped polypyrrole (PPy) films were electrochemically synthesized as novel biomimetic conductive materials capable of efficient electrical signaling and preferential biological interactions. Molecular weights (MWs) of HA varied in a wide range (35 × 103–2 × 106 Da) and critically determine chemical, electrochemical, and biological properties of PPy/HA. Especially, PPy films with low MW HA markedly support cell adhesion and growth, while PPy films with high MW HA are resistant to cell attachment. Furthermore, PPy/HA exhibits greatly improved tissue compatibility and in vivo EMG signal recording ability. We for the first time demonstrate that biomimetic PPy/HA-based biomaterials can serve as versatile and effective platforms for various biomedical applications, such as tissue engineering scaffolds and bioelectrodes.

Influence of Hyaluronic Acid Transitions in Tumor Microenvironment on Glioblastoma Malignancy and Invasive Behavior.

The extracellular matrix (ECM) is critical in tumor growth and invasive potential of cancer cells. In glioblastoma tumors, some components of the native brain ECM such as hyaluronic acid (HA) have been suggested as key regulators of processes associated with poor patient outlook such as invasion and therapeutic resistance. Given the importance of cell-mediated remodeling during invasion, it is likely that the molecular weight of available HA polymer may strongly influence GBM progression. Biomaterial platforms therefore provide a unique opportunity to systematically examine the influence of the molecular weight distribution of HA on GBM cell activity. Here we report the relationship between the molecular weight of matrix-bound HA within a methacrylamidefunctionalized gelatin (GelMA) hydrogel, the invasive phenotype of a patient-derived xenograft GBM population that exhibits significant in vivo invasivity, and the local production of soluble HA during GBM cell invasion. Hyaluronic acid of different molecular weights spanning a range associated with cell-mediated remodeling (10, 60, and 500 kDa) was photopolymerized into GelMA hydrogels, with cell activity compared to GelMA only conditions (-HA). Polymerization conditions were tuned to create a homologous series of GelMA hydrogels with conserved poroelastic properties (i.e., shear modulus, Poisson's ratio, and diffusivity). GBM migration was strongly influenced by HA molecular weight; while markers associated with active remodeling of HA (hyaluronan synthase and hyaluronidase) were found to be uninfluenced. These results provide new information regarding the importance of local hyaluronic acid content on the invasive phenotype of GBM.

Intra-articular viscosupplementation of hyaluronic acids in an experimental osteoarthritis model

ObjectiveTo analyze, from the immunohistochemical perspective, the effects of hyaluronic acid of different molecular weights in an experimental model of osteoarthritis in rabbits. MethodsForty-four male California rabbits were randomly assigned to three different groups (PR, S, and P) and submitted to the resection of the anterior cruciate ligament of the right knee. Three weeks after the surgical procedure, three intra-articular weekly injections were carried out with low-molecular-weight native hyaluronic acid (Hyalgan®) to PR group, high molecular weight branched chain hyaluronic acid (Synvisc®) to group S, and saline solution 0.9% to group P. All animals were sacrificed 12 weeks after the surgical procedure, and the tibial plateaus of the infiltrated knees were then dissected. Histological sections of cartilage from the tibial plateau support areas were stained with immunohistochemical markers in order to investigate the amount of metalloproteases (MMPs 3 and 13) and their inhibitors (TIMPs 1 and 3). The staining intensity was quantified on a Zeiss Imager.Z2 Metasystems microscope and analyzed by Metafer4 Msearch software. ResultsThe chondroprotective effect of the hyaluronic acids used in the study was demonstrated when compared to the control group. However, the comparison between them presented no significant statistical difference regarding chondroprotection. ConclusionThe injection of saline solution demonstrated signs of OA development, while adding native hyaluronic acid of low molecular weight (Hyalgan®) and hyaluronic acid of high molecular weight (Synvisc®) protected the articular cartilage in this model of OA.

Viscossuplementação intra‐articular de ácidos hialurônicos em modelo experimental de osteoartrite

ObjectiveTo analyze, from the immunohistochemical perspective, the effects of hyaluronic acid of different molecular weights in an experimental model of osteoarthritis in rabbits. MethodsForty‐four male California rabbits were randomly assigned to three different groups (PR, S, and P) and submitted to the resection of the anterior cruciate ligament of the right knee. Three weeks after the surgical procedure, three intra‐articular weekly injections were carried out with low‐molecular‐weight native hyaluronic acid (Hyalgan®) to PR group, high molecular weight branched chain hyaluronic acid (Synvisc®) to group S, and saline solution 0.9% to group P. All animals were sacrificed 12 weeks after the surgical procedure, and the tibial plateaus of the infiltrated knees were then dissected. Histological sections of cartilage from the tibial plateau support areas were stained with immunohistochemical markers in order to investigate the amount of metalloproteases (MMPs 3 and 13) and their inhibitors (TIMPs 1 and 3). The staining intensity was quantified on a Zeiss Imager.Z2 Metasystems microscope and analyzed by Metafer4 Msearch software. ResultsThe chondroprotective effect of the hyaluronic acids used in the study was demonstrated when compared to the control group. However, the comparison between them presented no significant statistical difference regarding chondroprotection. ConclusionThe injection of saline solution demonstrated signs of OA development, while adding native hyaluronic acid of low molecular weight (Hyalgan®) and hyaluronic acid of high molecular weight (Synvisc®) protected the articular cartilage in this model of OA.

Human skin penetration of hyaluronic acid of different molecular weights as probed by Raman spectroscopy.

Topical delivery of molecules into the human skin is one of the main issues in dermatology and cosmetology. Several techniques were developed to study molecules penetration into the human skin. Although widely accepted, the conventional methods such as Franz diffusion cells are unable to provide the accurate localization of actives in the skin layers. A different approach based on Raman spectroscopy has been proposed to follow-up the permeation of actives. It presents a high molecular specificity to distinguish exogenous molecules from skin constituents. Raman micro-imaging was applied to monitor the skin penetration of hyaluronic acids (HA) of different molecular weights. The first step, was the spectral characterization of these HA. After, we have determined spectral features of HA by which they can be detected in the skin. In the second part, transverse skin sections were realized and spectral images were recorded. Our results show a difference of skin permeation of the three HA. Indeed, HA with low molecular weight (20-300 kDa) passes through the stratum corneum in contrast of the impermeability of high molecular weight HA (1000-1400 kDa). Raman spectroscopy represents an analytical, non-destructive, and dynamic method to evaluate the permeation of actives in the skin layers.

Assessing the relative merits of mineralization and coagulation by Fenton process using humic acid of different molecular weights

In treating humic acid (HA) by Fenton process, we noticed that the process actually consists of dual functions of coagulation and mineralization. Hence, an attempt was made to clarify their relative contributions using HA of different molecular weights (MWs). Three ranges of MWs, namely, less than 100 k Da (sample A), less than 10 k Da (sample B), and less than 1 k Da (sample C), were investigated. Their initial DOC was 10 mg/L. By examining the reaction constants kM (for mineralization) and kC+M (for coagulation plus mineralization), three trends were observed. Firstly, kC+M and kM increased by increasing the dose of either Fe2+ or H2O2. Secondly, kC+M decreased with decreased MW. Lastly, kM increased with decreased MW. Therefore, Fenton mineralization for HA of smaller MW and Fenton coagulation for HA of larger MW are better for DOC removal. Specifically, the ratios of DOC removal from mineralization to that from coagulation (denoted by M/C) were 0.26–0.45, 0.52–1.36, and 1.0–6.29 for samples A, B, and C, respectively. That is, M/C of sample C > sample B > sample A; namely, the lower MW HA has a higher M/C ratio.

Effect of hyaluronic acids as chondroprotective in experimental model of osteoarthrosis

Objectiveto analyze the effects of hyaluronic acid of different molecular weights in an experimental model of osteoarthritis in rabbits. Methodsforty‐four male California rabbits were divided randomly into three groups and underwent resection of the anterior cruciate ligament in his right knee. After three weeks of the surgical procedure began three weekly intra‐articular injections of hyaluronic acid native (Polireumin®)‐PR, hyaluronic acid branched chain (Synvisc®)‐S and 0.9% saline‐P. All animals were sacrificed after twelve weeks of surgery and tibial plateau infiltrated the knees were dissected. Histological cartilage of the support areas of the tibial plateaus were stained with Alcian Blue pH 1.0, Alcian Blue pH=2.5 and toluidine blue for research on the amount of proteoglycans. The intensity of staining was quantified on a Zeiss microscope apparatus Imager Z2 MetaSystems and analyzed by software MetaferMsearch. Resultsthe effect of chondroprotetor hyaluronic acids used in the study was confirmed when compared to the control group, but the comparison made between them, there was no statistically significant difference regarding chondroprotetion. Conclusionthe hyaluronic acids tested had chondroprotective effect, with no statistical difference with regard to the different molecular weights.

Efeito dos ácidos hialurônicos como condroprotetores em modelo experimental de osteoartrose

Objectiveto analyze the effects of hyaluronic acid of different molecular weights in an experimental model of osteoarthritis in rabbits. Methodsforty-four male California rabbits were divided randomly into three groups and underwent resection of the anterior cruciate ligament in his right knee. After three weeks of the surgical procedure began three weekly intra-articular injections of hyaluronic acid native (Polireumin®)-PR, hyaluronic acid branched chain (Synvisc®)-S and 0.9% saline-P. All animals were sacrificed after twelve weeks of surgery and tibial plateau infiltrated the knees were dissected. Histological cartilage of the support areas of the tibial plateaus were stained with Alcian Blue pH 1.0, Alcian Blue pH = 2.5 and toluidine blue for research on the amount of proteoglycans. The intensity of staining was quantified on a Zeiss microscope apparatus Imager Z2 MetaSystems and analyzed by software MetaferMsearch. Resultsthe effect of chondroprotetor hyaluronic acids used in the study was confirmed when compared to the control group, but the comparison made between them, there was no statistically significant difference regarding chondroprotetion. Conclusionthe hyaluronic acids tested had chondroprotective effect, with no statistical difference with regard to the different molecular weights.

Stable (Cu, Mg) and radiogenic (Sr, Nd) isotope fractionation in colloids of boreal organic-rich waters

Stable (Cu and Mg) and radiogenic (Sr and Nd) isotopic compositions in filtrates and ultrafiltrates of various size fractions have been measured in waters of subarctic watersheds (NW Russia) and in temperate rivers and lakes of the south boreal zone. A large volume of samples were filtered in the field using cascade filtration and ultrafiltration employing progressively decreasing pore sizes (100, 20, 10, 5, 0.8, 0.4, 0.22, and 0.1μm; 100, 10 and 1kDa) followed by element isotopic analysis using thermal ionization mass spectrometers and a Neptune multicollector ICP-MS. In the boreal watershed underlain by Archean and Proterozoic rocks, the 87Sr/86Sr ratio decreased in the 1–100kDa ultrafiltrates and dialysates by 0.0001–0.0004 units compared to the 0.45μm filtrates. Despite the dominance of colloids in the Nd speciation in surface waters, the isotopic value of Nd in the filtrates and ultrafiltrates remained constant within the uncertainty of the measurements. We hypothesize the absence of an atmospheric input of silicate dust for Nd but the presence of marine aerosols for Sr. It follows that the Sr in the investigated surface waters has a short residence time compared to the time required for achieving isotopic equilibrium between the colloidal (1kDa–0.22μm) and truly dissolved (<1kDa) pools. For Nd, the residence time is long enough to achieve this equilibrium. The stable isotope composition of Cu in the streams remained constant within ±0.1‰ during filtration through 100μm to 1kDa membranes, despite the fact that 40–60% of Cu was colloidal. This result suggests that the homogeneity of the Cu isotopic composition within the colloidal and truly dissolved pools is likely associated with the similarity of the structure and stability of Cu(II) complexes with fulvic acids of different molecular weights. The stable isotope composition of dissolved Mg in soil solution and bog surface water demonstrates similar, within the analytical uncertainty, isotopic signatures between truly dissolved and colloidal fractions.Despite the dramatically different structures of the metal–dissolved organic matter (DOM) complexes for Cu2+ and Mg2+, the results of the present work reveal a high homogeneity of stable isotope compositions between colloidal (1kDa–0.22μm) and ultrafiltered (<1kDa) fractions, which is presumably due to the high rate of isotopic exchange between the colloidal and ionic forms of the metals. Variation of radiogenic isotopic composition of Sr among ultrafiltered, colloidal and particulate fractions suggests that there is a contribution of atmospheric input to the chemical composition of surface waters and provides certain constraints on the isotopic composition of Sr carried by small organic-rich boreal rivers to the Arctic Ocean.

Adhesion, phenotypic expression, and biosynthetic capacity of corneal keratocytes on surfaces coated with hyaluronic acid of different molecular weights

In ophthalmology, hyaluronic acid (HA) is an important extracellular matrix (ECM) component and is appropriate for use in generating a microenvironment for cell cultivation. The aim of this work was to evaluate the rabbit corneal keratocyte (RCK) growth in response to HA coatings under serum-free conditions. After modification with HA of varying molecular weights (MWs: 35–1500kDa), the surfaces were characterized by atomic force microscopy and contact angle measurements, and were used for cell culture studies. Our data indicated that the substrates coated with higher negatively charged HA become rougher and are more hydrophilic, resulting in the decrease of cell adhesion and cell–matrix interaction. This early cellular event was likely responsible for the determination of keratocyte configuration. Additionally, for the growth of RCKs on dry HA coatings with surface roughness of 1.1–1.7nm, a strong cell–cell interaction was observed, which may facilitate the formation of multicellular spheroid aggregates and maintenance of mitotically quiescent state. At each culture time point from 1 to 5days, a better biosynthetic capacity associated with a higher prevalence of elevated ECM production was found for the cells in a spherical configuration. Irrespective of polysaccharide MW of surface coatings, the RCKs presented good viability without hypoxia-induced death. As compared with a monolayer of adherent keratocytes on tissue culture polystyrene plates and low MW HA-modified samples, the cell spheroids (76–110μm in diameter) showed significantly higher expressions of keratocan and lumican and lower expressions of biglycan, similar to those of keratocytes in vivo. Moreover, the expression levels of corneal crystallin aldehyde dehydrogenase (7–9-fold increase) and nestin (10–16-fold increase) were greater in larger-sized spheroids, indicating higher ability to maintain cellular transparency and self-renewal potential. It is concluded that the cultured RCKs on surfaces coated with HA of different MWs can sense ECM cues, and the multicellular spheroids may potentially be used for corneal stromal tissue engineering applications.

Study on the influence of humic acid of different molecular weight on basic ion exchange resin's adsorption capacity

In this paper, humic acid (HA) was ultra-filtered into different molecular weight sections and was characterized by multi-element analysis, UV 254/TOC, FT-IR and three-dimensional fluorescence spectrometric. Since humic acids of different molecular weights have different hydrophilic and molecular size, the maximum adsorption capacity of basic ion exchange resins appears on the humic acid whose molecular weight ranges from 6000 to 10,000 Da.

The effect of hyaluronic acid on brushite cement cohesion

The improvement of calcium phosphate cement (CPC) cohesion is essential for its application in highly blood perfused regions. This study reports the effectiveness of hyaluronic acids of different molecular weights in the enhancement of brushite cement cohesion. The cement was prepared using a powder phase composed of a mixture of β-tricalcium phosphate and monocalcium phosphate monohydrate, whereas the liquid phase was formed by 0.5 M citric acid solution modified by the addition of hyaluronic acid of different molecular weights. It was found that medium and high molecular weight hyaluronic acid enhances the cement cohesion and scarcely affects the cement mechanical properties. However, concentrations >0.5% (w/v) were less efficient to prevent the cement disintegration. It is concluded that hyaluronic acid could be applied efficiently to reduce brushite cement disintegration.

Plant Uptake of Iron Chelated by Humic Acids of Different Molecular Weights

Mobilization of iron (Fe) chelated by humic acids (HA) of low (HA10,000) and high molecular weight (HA100,000) fractions and its uptake by plants were investigated in growth experiments with sunflower seedlings. The iron chelates (labeled with 59Fe) contained in dialysis bags (mw. cutoff=3500) were placed in minus iron Hoagland solutions as the Fe source and at the same time fulvic acid (FA), EDTA, and low and high molecular weight HA fractions were added in the solutions as mobilizators. Characterization of FA, HA10,000, and HA100,000 were performed by infrared spectroscopy and chemical analysis, e.g., total acidity, COOH, and phenolic‐OH content. Roots and leaves were harvested, dried, and ground for Fe activity determination. Iron contents and pH in the nutrient solutions were measured before and after treatments. The supply of Fe to the plants was apparently sufficient, because no Fe deficiency has been detected in the test plants but during the whole absorption period, the pH of the nutrient solution was about 4.5. The Fe contents in leaves indicated that part of the Fe was rapidly transported from roots to leaves. Judging from the Fe contents in leaves, it was assumed that the small size HA10,000 and EDTA were the most efficient in affecting transport of Fe from root to leaf tissue. FA, HA10,000, and especially HA100,000 were unable to penetrate the dialysis bags and, hence, were effective in Fe mobilization only after the Fe, dissociated from the Fe‐HA chelate, has passed the dialysis membrane into the nutrient solutions. In contrast, the small size EDTA was expected to have penetrated the dialysis bags, permitting mobilization of chelated Fe by ligand exchange inside the bags, and transporting the Fe to the roots. The results suggested that the humic substances used in this study were able to form with the Fe3+ ion complexes that maintained the iron available to the sunflower plants. In the chemical form of Fe.L, where L was FA o HA, the iron within the bags or in solution or in the roots free space, was available for exchange reactions with the natural sunflower plant chelators for its transport to the leaves.

Modelling of natural and synthetic polyelectrolyte interactions in natural waters by using SIT, Pitzer and Ion Pairing approaches

In this paper SIT and Pitzer models are used for the first time to describe the interactions of natural and synthetic polyelectrolytes in natural waters. Measurements were made potentiometrically at 25 °C in single electrolyte media, such as Et 4NI and NaCl (for fulvic acid 0.1 < I /mol L − 1 < 0.75), and in a multi-component medium simulating the composition of natural waters at a wide range of salinities (for fulvic and alginic acids: 5 < S < 45) with particular reference to sea water [Synthetic Sea Water for Equilibrium studies, SSWE]. In order to simplify calculations, SSWE was considered to be a “ single salt” BA, with cation B and anion A representing all the major cations (Na +, K +, Mg 2+, Ca 2+) and anions (Cl −, SO 4 2−) in natural sea water, respectively. The ion pair formation model was also applied to fulvate and alginate in artificial sea water by examining the interaction of polyanions with the single sea water cation. Results were compared with those obtained from previous speciation studies of synthetic polyelectrolytes (polyacrylic and polymethacrylic acids of different molecular weights). Results indicate that the SIT, Pitzer and Ion Pairing formation models used in studies of low molecular weight electrolytes may also be applied to polyelctrolytes with a few simple adjustments.

Studies on corrosion inhibition of aluminum in 1.0 M HCl and 1.0 M H 2SO 4 solutions by ethoxylated fatty acids

The inhibition of three ethoxylated fatty acids of different molecular weights on the corrosion of aluminum in both 1.0 M HCl and 1.0 M H 2SO 4 solutions have been studied at different temperatures (25–55 °C) by means of weight loss and potentiodynamic polarization techniques. The inhibition efficiency for the three fatty acids increase with the increase in the inhibitors concentration but decreases with increasing temperature. The inhibition efficiency for the three inhibitors decreases in the order ( n=20, 40, 80): OL[ EO] 80> OL[ EO] 40> OL[ EO] 20 The inhibition occurs through adsorption of the inhibitor molecules on the metal surface without modifying the mechanism of corrosion process. Frumkin adsorption isotherms fit well the experimental data of dissolution and adsorption were calculated and discussed.

Complex formation of polyvinyl ether of diethylene glycol with polyacrylic acid II. Effect of molecular weight of polyacrylic acid and solvent nature

In the present work the complexation between polyvinyl ether of diethylene glycol and polyacrylic acid of different molecular weights has been studied in aqueous and isopropanol solutions. It was found that the polyacrylic acid with molecular weight 2000 does not form interpolymer complexes. The stability of polycomplexes in respect to addition of different solvents was evaluated. It was shown that depending on the nature of polymers the interpolymer complexes may be more or less stable in aqueous solutions than in organic ones.

Ultra-low dosage flocculation of alumina using polyacrylic acid

Flocculation experiments conducted with alumina suspensions using polyacrylic acids of different molecular weights showed that flocculation and dispersion can be obtained with both low and high molecular weight polymers depending on the dosage and other solution conditions. While as expected, low molecular weight (5000 g mol −1) polyacrylic acid effectively dispersed alumina suspensions at normal dosages, higher molecular weight moieties (50 000 g mol −1 and above) caused flocculation. Surprisingly, marked flocculation was obtained with parts per billion level polymer dosage. At such ultra-low dosages, a minimum in flocculation was observed at ∼pH 4.5 close to the reported p K a of polyacrylic acid. Zeta potential results did not reveal any significant change in the electrokinetic properties of alumina particles due to the presence of low dosage of polyacrylic acid, only at higher dosages charge reversal occurred. Partial charge neutralization coupled with hydrogen bonding is postulated to be the mechanism for the flocculation obtained at the ultra-low dosages. At the highest dosages, crowding of the polymer segments at the solid/liquid interface results in poor flocculation especially in the acidic pH range.