Quantity Of Carboxyl Groups Research Articles

Preparation of a water-based carboxylated Poly(phthalazione ether nitrile) sizing agent for interfacial reinforcement of CF/PPESK composites

This study focuses on synthesizing a range of hydrolysis-modified poly(phthalazione ether nitrile) polymers with different quantities of carboxyl groups (HPPEN-COOH). These polymers are intended to enhance the bonding strength between carbon fibers (CFs) and poly(phthalazine ether sulfone ketone) (PPESK). The chemical structure of HPPEN-COOH was elucidated using FTIR spectroscopy, and the presence of HPPEN-COOH as a coating on the CFs surface was confirmed by XPS analysis. Compared with the UCF/PPESK composite, the interlaminar shear strength of the CF-5/PPESK composite increased by 39 %. In the DMA test, the service temperature and storage modulus of the CF-5/PPESK composite were increased to 268 °C and 112 GPa, respectively. Furthermore, the composite showed satisfactory performance in hydrothermal aging studies. This method is simple and easy to implement, has the potential for large-scale industrial production, and is an environmentally friendly method to improve the interface properties of the CF/PPESK composite.

Kinetic and isotherm studies for nickel ions’ biosorption by jute fabrics

Raw jute fabric was chemically modified with 1 % NaOH for 30 min, 17.5 % NaOH for 5 min or with 0.7 % NaClO2 for 30 and 60 min to study the influence of changes in the chemical composition of the fabrics and quantity of carboxyl groups on the biosorption capacity of the fabrics for nickel ions. The effects of contact time and initial concentration of nickel ions on the biosorption capacity of the fabrics were also investigated. The obtained results revealed that the biosorption of nickel ions can be explained by the pseudo-second- order kinetic model, while the experimental isotherm data fit better with the Langmuir model. The calculated ratios between maximal biosorption capacity (6.30?12.06 mg g-1) of the jute fabrics and carboxyl group quantity indicated that approximately half of the carboxyl groups of the fabrics? would be involved in binding nickel ions during biosorption. Therefore, the quantity of carboxyl groups can be used to predict the maximal biosorption capacity of jute fabrics toward nickel ions. In the case of oxidized jute fabrics, the lignin removal, and consequently increased content of cellulose and hemicelluloses, also contributed to a higher biosorption capacity.

A versatile porous 3D polyurethane/polyacrylic acid (PU-PAA) membrane for one-step multiple contaminants water purification

Developing versatile materials for simultaneous removal of organic dyes, heavy metals and oil from water has big significance for water protection. Herein, we fabricate a porous 3D polyurethane/polyacrylic acid (PU-PAA) membrane by simple solvent casting-salt leaching and thermal crosslinking, which combines the properties of underwater superoleophobicity and quantities of carboxyl groups. The stable superoleophobicity can be used for efficient surfactant-stabilized oil-in-water microemulsions separation. And the negative carboxylic ions are able to capture cationic dyes and heavy metals, simultaneously. Using the PU-PAA membrane in filtration column enables one-step multiple pollutants water treatment with high flux, selectivity, recyclability, efficiency and capacity. Moreover, PU-PAA can be used for efficient dye mixture separation. These results indicate that this versatile porous 3D membrane can be a very potential candidate for advanced purification applications.

VIBROMAGNETIC EXTRACTION OF HYMATOMELANIC ACIDS FROM SAPROPEL AND INVESTIGATION OF THEIR STRUCTURAL AND MOLECULAR COMPOSITION

The aim of this investigation was to study the influence of vibromagnetic extraction on the qualitative and quantitative composition of the hymatomelanic acids (HMA) obtained from the sapropel of Karasevoye lake (Russia, Tomsk Region, Chazhemto). HMA were extracted using two methods: continuous mechanical stirring and vibromagnetic extraction. It is reported that the use of vibromagnetic extraction increases the yield of HMA in 2.62 times. Functional composition of the HMA, obtained from sapropel by vibromagnetic extraction, was characterized using thermogravimetric analysis and infrared spectroscopy. It has been revealed that content of aliphatic fragments prevails in the structure of the HMA over content of condensed fragments. It has been shown that aliphatic fragments of HMA comprises an increased quantity of carboxyl groups. GC-MS method was used to determine content of carboxylic acids in the composition of the HMA fractions, extracted by various methods. It is reported that HMA of sapropel obtained by vibromagnetic extraction comprises 9 carboxylic acids, and their total content is 1.8 times higher compared to HMA obtained by continuous mechanical stirring. An information obtained during this investigation can be further used to create cosmetic and therapeutic products based on sapropel, and analytical methods for controlling production of such products.

Conductive poly(pyrrole-co-(1-(2-carboxyethyl)pyrrole)) core-shell particles: Synthesis, characterization, and optimization

Abstract Functional conductive polymers such as poly(pyrrole-co-(1-(2-carboxyethyl)pyrrole)) (P(Py-PyCOOH)) copolymer has raised significant research interests in biomedical field for their electrical conductivity, biocompatibility, and functionality that facilitates further biological modifications. However, most P(Py-PyCOOH) polymers are synthesized through electropolymerization with small sample size and low productivity. In this work, the core-shell P(Py-PyCOOH) particles were synthesized through a simple one step emulsion polymerization. Experimental parameters including the ratio of water/oil, feeding of FeCl3 and functional monomers, as well as reaction time were evaluated to define the balanced optimal conditions. The obtained P(Py-PyCOOH) particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and total elements analysis. The particles present a core-shell structure comprising the pyrrole (Py) dominated P(Py-PyCOOH) copolymer as the core and PPyCOOH homopolymer as the shell. Given the composition of the shell, the quantity of carboxyl groups on particle surface already reached maximum; further polymerization of excessive functional monomers would not increase any surface functionality but decrease conductivity of the particles. To conclude, the core-shell P(Py-PyCOOH) particles possess a good conductivity (>10−3 S cm−1), maximized surface functionality, large surface area, excellent dispersibility in water, and high overall yield. Such conductive particles can be good candidate for sensing and biomedical applications.

Polyurethane modification with acrylic acid by Ce(IV)-initiated graft polymerization

AbstractThis paper presents a method for polyurethane surface functionalization for tissue engineering applications. Functionalization has been carried out by grafting acrylic acid to the polyurethane surface with the use of radical polymerization with a Ce4+ initiator. Contrary to other papers suggesting that the presence of hydroxyl groups are essential for successful grafting via ceric ions, we propose a method with the omission of the surface hydroxylation step. The influence of reaction conditions: reaction time, reaction temperature and monomer concentration on carboxyl groups surface density has been analyzed and described. The quantity of carboxyl groups on the surface was determined with the use of the TBO method. Materials grafted with acrylic acid have been subjected to conjugation with a peptide using sulfoNHS/ EDC chemistry. Successful incorporation of the peptide has been confirmed by an ELISA assay. Additionally, for better characterization, after each step of modification materials were subjected to SEM, FTIR-ATR, XPS and contact angle measurement analysis.

Dissolution of lignite in ionic liquid 1-ethyl-3-methylimidazolium acetate

The extraction behaviors of three lignites with ionic liquid (IL)-1-ethyl-3-methylimidazolium acetate (EMIA) were studied in this work. The effects of extraction temperature and lignite type on extract yield and product compositions were primarily investigated. Also the relationship between the extract yield of lignites and the quantities of oxygen-containing functional groups in lignites was investigated. It was found that EMIA is a more efficient solvent for the dissolution of lignites compared to the performance of 1-butyl-3-methyl-imidazolium chloride (BMIC). Extraction temperature and lignite type significantly affect extraction behaviors of lignite with EMIA. The extract yield of lignites with EMIA increases with the quantity of carboxylic groups in lignite increases. Only a small amount of aliphatic alkyl structure components are extracted at low temperature. More aromatic structure components are extracted by EMIA at high extraction temperature.

Oxidation and Self-Reaction of Carboxyl Groups During Coal Spontaneous Combustion

Carboxyl groups play an important role during the development of coal self-heating. The real-time changing characteristics of carboxyl groups were obtained using an in situ Fourier Transform Infrared Spectroscopy method. They are significantly influenced by reaction atmospheres. Under dry-air atmosphere, their quantity obviously decreases before reaching 120°C and then increases with temperature rise. Under oxygen-free atmosphere, it decreases before reaching 80°C and then increases with temperature rise. In contrast with direct oxidation process, the quantity of carboxyl groups is smaller and the decrease phenomenon at the beginning almost disappears during the oxidation process following oxygen-free reaction. The results indicate that the carboxyl groups have different reaction pathways during coal self-heating. These pathways can be divided into two kinds, that is, oxidation pathways and self-reaction pathways. The study proposed the reaction sequences of carboxyl groups during coal self-heating, which are helpful for revealing the mechanism of coal spontaneous combustion.

Characterisation of Kraft lignin separated by gradient acid precipitation

Lignin is considered the second most abundant organic natural compound in the world. Lignin represents a promising source of new materials based on renewable resources. Currently the lignin is used in low value-added applications and for energy production and chemical recycling for industrial process itself in production of pulp and paper. Only a small amount is being used for other applications. The aim of this study was to analyze the effects of precipitation on the composition of lignin extracted from black liquor produced in industry CMPC Celulose Riograndense. For this, lignins were precipitated at different pH conditions, with various acids. Obtained lignin samples were characterized by various analytical techniques such as FTIR, GPC, HPLC and XRD. Furthermore, the quantity of carboxyl groups was also analyzed. The antioxidant activity of the analyzed lignins was evaluated by the radical ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) assay. Total phenolic contain was evaluated by Folin–Ciocalteu method while the antioxidant potential of lignins was measured by DPPH. The lignins showed a variable composition according to the acid used for its precipitation; the lignin precipitated with sulphuric acid presented Na2SO4 salts while with hydrochloric acid, NaCl was found. In addition, a change in lignin composition was observed at different pH.

Adsorption of Polyacrylic Acid and Its Copolymers with Acrylonitrile on Zinc Oxide Particles

Adsorption of polyacrylic acid and its copolymers with acrylonitrile, containing different quantities of carboxyl groups, on the dispersion of zinc oxide was investigated. The kinetics of polymer desorption was investigated based on data concerning the change in concentration of free carboxylic groups of polymer and zinc ions in solution. The concentration of free carboxyl groups decreases and the concentration of zinc ions in the liquid phase above the residue after separation of zinc oxide particles increases with time, reaching a constant value. The dependence of the concentration of free carboxyl groups and zinc ions in the liquid phase on the initial concentration of polymer in the plateau section of the kinetic curve was investigated. Adsorption isotherms of copolymers depend on their solubility in water and can be described by different mathematical models.

Enzymatic degradation and immunogenic properties of derivatized dextrans

Dextran T40 was modified with carboxylic, benzylamide and benzylamine-sulphonated groups (samples 1–10). The polymers were incubated with dextranase and the decrease of molecular weight was determined by high performance size exclusion chromatography. It was shown that the higher the substitution of dextrans, the lower their degradability. Modification of dextran with benzylamine and benzylamine-sulphonated groups appeared to hinder the formation of the enzyme-substrate complex more than the same quantity of carboxylic groups. The immunogenicity of one of the modified dextrans, containing 54% of carboxylic groups and 19.5% of benzylamine-sulphonated groups, was determined after subcutaneous and intravenous administration into Balb/c mice. The antibody titre was very low even if administered in complete Freund's adjuvant and did not depend on the injected dose. On the average, the titres of antibodies were lower by five orders of magnitude compared to bovine gamma globulin.