Neutralization Of Carboxyl Groups Research Articles

Preparation of excellent-water-resistance water-borne alkyd/acrylic hybrid coatings with varied maleic anhydride content

Water-borne alkyd/acrylic hybrid resins with varied maleic anhydride (MA) content were synthesized from the reaction between alkyd intermediate (AK) and maleic anhydride modified acrylic prepolymer (AC) followed by neutralization of carboxyl groups with triethylamine. Water-borne alkyd/acrylic hybrid resins were characterized by nuclear magnetic resonance (NMR), infrared spectrum (IR), transmission electron microscope (TEM), gel permeation chromatography (GPC), laser diffraction particle size analyzer, rheometer and thermogravimetric analysis (TGA). In addition, air-drying water-borne coatings were prepared using the above-mentioned dispersions and their coatings properties were evaluated. The results showed that the microstructure of the water-borne alkyd/acrylic hybrid dispersion was loose cotton type, which induced the accessibility of fatty acid chains to oxygen is unimpeded, therefore, higher cross-linking density would be obtained and resulted in the coating with optimum MA content exhibited excellent physical properties and water resistance, up to 32 days, which is better than the water resistance of all water-borne alkyd coatings or modified water-borne alkyd coatings reported up to now, and also better than the water resistance of the commercial water-borne alkyd/acrylic hybrid coating.

Needleless electrospinning of poly(acrylic acid) superabsorbent: Fabrication, characterization and swelling behavior

In this work, nanofibrous hydrogel has been fabricated from needleless electrospinning of Poly(acrylic acid) (PAA) in an aqueous solution with different concentrations. First, all solution samples were characterized for pH, surface tension, conductivity and viscosity. Next, electrospinnability of the PAA-water dope solution was investigated using the needleless electrospinning technique under constant conditions. Results indicated that the PAA-water solution was not electrospinnable. Therefore, the neutralization of carboxylic groups in the PAA chemical structure using the NaOH solution was investigated to enhance the PAA electrospinnability. Morphology observation revealed that the fiber diameters ranged from 40 to 250 nm and increased with increasing the solution concentrations. Increasing the neutralization degree (10%, 15% and 20% with 50 wt% NaOH solution) led to increase the dope viscosity and conductivity. The resultant nanofibers could be rendered water-insoluble by incorporating 1,4-butanediol diglycidyl-ether in the PAA-water dope solution, then heat-induced crosslinking was performed using a microwave at different curing times (1–5 min) and temperatures (45–105 °C). The nanofibrous hydrogel mat was then characterized by FTIR. The resulting nanofibrous hydrogel showed remarkable water absorption capacity up to 17,000% and 51,000% (within 15 min) in the standard saline solution and distilled water, respectively.

Enhancement of As(V) adsorption onto activated sludge by methylation treatment

Biosorption properties of arsenate [As(V)] onto activated sludge were investigated in batch systems. The adsorption of As(V) onto sludge increased from 23 to 266 microg/g dry weight through the methylation of the activated sludge. This increase resulted from neutralization of carboxylic groups via the methylation process. The pH effect of As(V) uptake was also investigated and As(V) adsorption by methylated sludge decreased significantly at high pH (pH > 11) due to competition between As(V) and OH(-) ions for binding sites distributed on sludge surfaces. In contrast, low pH favored As(V) adsorption by methylated sludge because of the elevated quantities of positively charged functional groups. The results suggest that methylated activated sludge may provide promising applications for the simultaneous removal and separation of As(V) from aqueous effluents.

Dynamic mechanical and thermal characteristics of homopolymers and copolymers containing arylene ether ketone units with carboxylic side groups and their salts

Properties of a poly(arylene ether ketone) with carboxyl side groups, copolymers containing units of this homopolymer, and their salts with different degrees of neutralization by alkali metals were studied by the methods of dynamic mechanical analysis, thermogravimetric analysis, and differential scanning calorimetry. By varying the nature of a metal atom and the degree of neutralization of carboxylic groups of a homopolymer and their content in copolymers, one may change the properties of polymers, including their ability to form ion pairs and, hence, their glass transition temperatures. For polymer salts at the 100% neutralization of carboxylic groups, the storage modulus and the glass transition temperature are shown to increase with decreasing the radius of the metal ion. The thermal stability of poly(arylene ether ketone) with carboxylic side groups and copolymers with different contents of such groups may be controlled by varying the nature and content of the introduced metal.

Synthesis of water‐reducible acrylic–alkyd resins based on modified palm oil

AbstractWater‐reducible acrylic–alkyd resins were synthesized from the reaction between monoglycerides prepared from modified palm oil and carboxy‐functional acrylic copolymer followed by neutralization of carboxyl groups with diethanolamine. Modified palm oil was produced by interesterification of palm oil with tung oil at a weight ratio of 1 : 1, using sodium hydroxide as a catalyst, whereas carboxy‐functional acrylic copolymer was prepared by radical copolymerization of n‐butyl methacrylate and maleic anhydride. The amount of acrylic copolymer used was from 15 to 40% by weight, and it was found that homogeneous resins was obtained when the copolymer content was 20–35 wt %. All of the prepared water‐reducible acrylic–alkyd resins were yellowish viscous liquids. Their films were dried by baking at 190°C and their properties were determined. These films showed excellent water and acid resistance and good alkali resistance. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1170–1175, 2005

Surface Grafting of Polyesters onto Carbon Nanofibers and Electric Properties of Conductive Composites Prepared from Polyester-grafted Carbon Nanofibers

The grafting of polyesters onto carbon naonfiber, such as vapor grown carbon fiber (VGCF) and high density VGCF (HDVGCF), by the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides initiated by potassium carboxylate (COOK) groups previously introduced onto these surfaces was investigated. The introduction of COOK groups onto these carbon nanofiber surfaces was successfully achieved by the neutralization of carboxyl groups with KOH. Carboxyl groups were introduced onto these surfaces by oxidation of these nanofibers with nitric acid and mixture of nitric acid with sulfuric acid. It was found that the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was successfully initiated by COOK groups on the surface to give the corresponding polyester-grafted carbon nanofiber. The dispersibility of carbon nanofiber in THF was remarkably improved by the grafting of polyesters onto the surface. The electric resistance of composite prepared from the polyester-grafted carbon nanofiber and poly(ethylene glycol) suddenly increased in methanol vapor over 103 times, and returned to initial resistance when it was transferred into dry air. These results indicate that the composite can be used as a novel gas sensor.

Structure and properties of polyamide 6 blends with low‐density polyethylene grafted by itaconic acid and with neutralized carboxyl groups

AbstractA comparative study of the structure and properties of two‐phase blends of polyamide 6 (PA6) and low‐density polyethylene (LDPE) modified in the course of reactive extrusion, by grafting of itaconic acid (IA) without neutralization of carboxyl groups (LDPE‐g‐IA) and with neutralized carboxyl groups (LDPE‐g‐IA−M+) was carried out. It was shown that 30 wt % of LDPE‐g‐IA−M+ introduced to PA6 resulted in blends of higher Charpy impact strength compared with that of PA6/LDPE‐g‐IA blends. The maximum increase was achieved when Mg(OH)2 was used as a neutralizing agent. The blend morphology has a two‐phase structure with blurred interphases because of increased adhesion between the phases. The neutralization of carboxyl groups in grafted IA did not lead to two‐phase morphology of blends, which had a negative influence on the mechanical properties. It is believed that the differences in the impact strength were caused by the influence of the added neutralizing agents on the structure of interphases, which depends on both the interfaces adhesion and structural effects resulting from the nucleating behavior of the neutralizing agent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1702–1708, 2004

Grafting of itaconic acid onto LDPE by the reactive extrusion: Effect of neutralizing agents

AbstractGrafting of itaconic acid (IA) onto low‐density polyethylene (LDPE) was performed by reactive extrusion where the initiator was dicumyl peroxide, and the neutralizing agents (NAs) were zinc oxides and hydroxides as well as magnesium oxides and hydroxides. The carboxyl groups were neutralized in molten LDPE directly in the course of acid grafting, and in prefabricated functionalized polyethylene (LDPE‐g‐IA). It was found that neutralizing agents introduced into the initial reaction mixture increase the yield of LDPE‐g‐IA while the carboxyl groups were neutralized partially or totally through chemical reactions. The physical structure of LDPE‐g‐IA did not in fact suffer any substantial changes. From the standpoint of neutralization activity, the NAs studied could be arranged as follows: Zn(OH)2 > ZnO > Mg(OH)2 > MgO. NA, added into the initial reaction mixture improved the grafting efficiency of IA onto LDPE. In case of the one‐step process (neutralization simultaneously with grafting), the neutralizing effect appears stronger than that in the two‐step process (neutralization of prepared LDPE‐g‐IA). This means that neutralization of carboxyl groups in IA was less effective when NA was introduced into LDPE‐g‐IA than for the case of the initial reactive mixture. Chemical neutralization of grafted IA results in products of improved resistance to thermal oxidation and thermal stability of melt. This result is of practical importance to the opportunities for widening the application range for PE modified by grafting IA, while preparing polymer blends to be compounded, processed, and used at elevated temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 828–836, 2003

Rheological behavior and microstructure of aqueous suspension of carboxylated core-shell structured latex particle

Core-shell type carboxylated particles form a flocculated structure in aqueous suspension with neutralization of carboxyl groups. Rheological behaviors of the suspension have been studied at various temperatures, and microstructures of the suspension have been discussed from the rheological behaviors and SAXS measurements. At 25°C, G' is larger than G in all ω regions, and G' is almost independent of ω, and the diffraction peak is detected by SAXS. These results mean that a three-dimensional network of interconnected lattice-like flocculated structure is formed. With increasing temperature, ω dependency of G' becomes stronger and distance of the particles of the structure does not changed. These mean the network linkage is disrupted partially by thermal motion, and the interconnected lattice-like flocculated structure changes to an isolated lattice-like one with increasing temperature. With increasing the degree of neutralization, an isolated structure changes to an interconnected three-dimensional structure decreasing the thermal motion just like decreasing temperature.

Polymerization of Antarctic fish tubulins at low temperatures: role of carboxy-terminal domains.

We have proposed previously that the efficient polymerization of tubulins from Antarctic fishes at low, physiological temperatures (-1.8 to +2 degrees C) may result in part from adaptations (e.g., reductions in acidic residues) located in their carboxy-terminal (C-terminal) tails [Detrich & Overton (1986) J. Biol. Chem. 261, 10922-10930]. To test this hypothesis, we have examined the polymerization of Antarctic fish neural tubulins modified at their C termini by proteolysis or by neutralization of carboxyl groups. Addition of subtilisin to low concentrations of Notothenia coriiceps tubulin induced a biphasic assembly reaction: stage I corresponded to the C-terminal cleavage of beta chains to produce alpha beta s dimers, and stage II coincided with the slower, C-terminal cleavage of alpha chains to yield alpha s beta s. Both stage I and stage II polymers consisted of protofilament sheets and microtubules with attached sheets. The critical concentration for assembly of the stage II polymer was at least 10-fold lower than that of untreated tubulin. Neutralization of Glu and Asp carboxyls in Gobionotothen gibberifrons microtubules by the carbodiimide-catalyzed incorporation of glycine ethyl ester (GEE) moieties produced a tubulin, modified largely in its C termini, that assembled more readily than did control tubulin. When 12 GEE groups were incorporated per dimer, the critical concentrations for assembly of modified tubulin at 5-10 degrees C were 2-3-fold smaller than those for the unmodified protein. Comparably modified bovine tubulin (10 GEE/dimer) assembled at 37 degrees C with a critical concentration 2.6-fold lower than that for the unmodified tubulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Surface charge potentiates conduction through the cardiac ryanodine receptor channel.

Single channel currents through cardiac sarcoplasmic reticulum (SR) Ca2+ release channels were measured in very low levels of current carrier (e.g., 1 mM Ba2+). The hypothesis that surface charge contributes to these anomalously large single channel currents was tested by changing ionic strength and surface charge density. Channel identity and sidedness was pharmacologically determined. At low ionic strength (20 mM Cs+), Cs+ conduction in the lumen-->myoplasm (L-->M) direction was significantly greater than in the reverse direction (301.7 +/- 92.5 vs 59.8 +/- 38 pS, P < 0.001; mean +/- SD, t test). The Cs+ concentration at which conduction reached half saturation was asymmetric (32 vs 222 mM) and voltage independent. At high ionic strength (400 mM Cs+), conduction in both direction saturated at 550 +/- 32 pS. Further, neutralization of carboxyl groups on the lumenal side of the channel significantly reduced conduction (333.0 +/- 22.5 vs 216.2 +/- 24.4 pS, P < 0.002). These results indicate that negative surface charge exists near the lumenal mouth of the channel but outside the electric field of the membrane. In vivo, this surface charge may potentiate conduction by increasing the local Ca2+ concentration and thus act as a preselection filter for this poorly selective channel.

Curing of Polyfunctional Spiro Ortho Esters by Carbon Black

The crosslinking reaction of polyfunctional spiro ortho esters (SOE) i.e., polymers (resins) that bear SOE structure, by carbon black was investigated. The copolymers of 2-methylene-1,4,6-trioxaspiro[4.6]undecane with vinyl monomers were crosslinked in solution upon heating (150°C) together with carbon black to give gels. Furthermore, carbon black was found to be able to cure the SOE resins, which are prepared from epoxy resins and ε-caprolactone, at 120—180°C in bulk. The curing ability of carbon black was enhanced with an increase in the content of carboxyl and phenolic hydroxyl groups on carbon black. By the neutralization of carboxyl group on carbon black, the curing ability of the carbon black decreased remarkably. Carbon black lost the curing ability upon the blocking of both carboxyl and phenolic hydroxyl group by the treatment with diazomethane. Based on these results, it was concluded that both carboxyl and phenolic hydroxyl groups on carbon black play an important role in the curing of polyfunctional SOE resins.

Hydration of polyacids.

AbstractThe hydration of several polyacids has been investigated with special attention to the effects of neighboring charged groups and hydrophobic groups on the hydration regions. The molar volume change due to the structural change of water by the hydration was obtained by the method of refractivity measurement. The polyacids employed were poly(acrylic acid), poly(methacrylic acid), poly(L‐glutamic acid), and a copolymer of maleic acid and vinyl acetate. The measurement of the refractive index was performed for the solutions of these polymers neutralized to varying degrees by tetrabutyl‐ammonium hydroxide and sodium hydroxide. The results confirm the characteristics of the previous model of the hydration of polyelectrolytes, that is, the cooperative action of neighboring charged groups induce the second hydration region in addition to the intrinsic hydration region. The stiff structure of water in these regions restricts the mobility of counterions forced to enter into these regions by the strong electrostatic potential of polyions. The results indicate also that hydrophobic groups induce an additional hydration region around their neighboring charged groups. Small but negative volume changes were observed for conformational changes of poly(L‐glutamic acid) and poly(methacrylic acid) induced by the neutralization of carboxyl groups.