COOH Functional Groups Research Articles

Short-time plasma surface modification of HDPE powder in a Plasma Downer Reactor – process, wettability improvement and ageing effects

The effectiveness of improving the wettability of HDPE powders within less than 0.1 s by plasma surface modification in a Plasma Downer Reactor is investigated. A correlation is revealed between the XPS results (O/C-ratio) and the wettability (contact angle, polar surface tension by capillary rise method). The O 2-content in the plasma feed gas has been adjusted for best wettability properties. XPS results indicate the formation of C O and COOH functional groups on the powder surface. The O/C-ratio increased from 0.0 (no oxygen on the non-treated powder) up to 0.15 for the plasma treated HDPE powder surface. With pure O 2-plasma treatment, a water contact angle reduction from >90° (no water penetration into the untreated PE powder) down to 65° was achieved. The total surface free energy increased from 31.2 to 45 mN/m. Ageing of treated powders occurs and proceeds mostly within the first 7 days of storage. Contact angle measurements and O1s/O2s intensity ratio data support that ageing is mainly a diffusion-controlled process. Nevertheless, XPS results show the presence of oxygen functional groups even after 40 days, which explains why the powder is still dispersible in water without any addition of surfactants.

Influence of Plasma Functionalization of Poly(propylene) with Acrylic Acid on the Nucleation of CaCO3

AbstractSummary: Poly(propylene) surfaces were modified by polymerization of acrylic acid using an RF plasma technique. Whereas a stable and reproducible hydrophilicity is obtained even after short treatment times, the thickness of the deposited layer, and thus the concentration of COOH functional groups per substrate surface area, increases with plasma exposure time. The modified‐poly(propylene) samples were exposed to aqueous solutions supersaturated with respect to CaCO3. Even though the polymer surfaces show a significant affinity for the adsorption of Ca2+ ions, the density of nucleation sites for calcite is reduced in comparison to untreated poly(propylene). This result can be explained by the special conditions in porous (“gelatinous”) growth media and high disorder provided by the plasma‐polymerized layers.AFM surface profile of a poly(propylene) surface (*) and film segments of plasma‐polymerized acrylic acid (**).imageAFM surface profile of a poly(propylene) surface (*) and film segments of plasma‐polymerized acrylic acid (**).

Rotational Diffusion of Coumarins in Electrolyte Solutions: The Role of Ion Pairs

In an attempt to explore how electrolyte ions influence the friction experienced by solutes with different functional groups, rotational diffusion of two structurally similar coumarins, coumarin 343 (C343) and coumarin 334 (C334), has been studied in dimethyl sulfoxide (DMSO) at several concentrations of LiNO3. The two coumarins are almost identical except for the different functional groups in the 3-position; C343 has −COOH whereas C334 has −COCH3. Because of the presence of the −COOH functional group, C343 exists as both anionic and neutral species in DMSO. Although both anionic and neutral forms of C343 exist in the ground state, C343 predominantly exists as neutral species in the excited state. The measured reorientation time of C343 in DMSO is slower by a factor of 2 compared to that of C334 due to the hydrogen bonding between the −COOH group of the probe and sulfoxide group of the solvent. However, the viscosity normalized reorientation times (τr/η) of C343 in LiNO3/DMSO solutions increase by 60% to 70% compared to that in pure DMSO. Addition of electrolyte ions shifts the equilibrium toward the anionic form of C343, which in turn forms ion pairs with Li+, and the large increase in τr/η values is due to the association of DMSO solvent molecules with these ion pairs. On the other hand, τr/η values of the neutral solute, C334, remain invariant in the entire range of the electrolyte concentration. The C343-Li+ ion pairs have been characterized using ab initio molecular orbital methods. Two approaches have been employed to model the friction experienced by the C343-Li+ ion pairs. In the first approach, the complex formed between C343-Li+ and the solvent molecules is treated as a rigid entity and the increase in the viscosity normalized reorientation time has been accounted for solely as an enhancement in the mechanical friction. Alternatively, the solvent association with the C343-Li+ ion pairs has been modeled as dielectric friction using the extended charge distribution theory.

Design of TiO 2 nanoparticle self-assembled aromatic polyamide thin-film-composite (TFC) membrane as an approach to solve biofouling problem

Microbial biofouling is one of the major obstacles for reaching the ultimate goal to realize high permeability over a prolonged period of reverse osmosis operation. In this study, the hybrid thin-film-composite (TFC) membrane consisted of self-assembly of TiO 2 nanoparticles with photocatalytic destructive capability on microorganisms was devised as a novel means to reduce membrane biofouling. Then, the anti-fouling and fouling mitigation on the actual commercialized TFC was verified. TiO 2 nanoparticles of a quantum size (∼10 nm or less) in anatase crystal structure were prepared from the controlled hydrolysis of titanium tetraisopropoxide and characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). Hybrid thin-film-composite (TFC) membrane was prepared by self-assembly of the TiO 2 nanoparticles through coordination and H-bonding interaction with the COOH functional group of aromatic polyamide thin-film layer, which was ascertained by X-ray photoelectron spectroscopy (XPS). The hybrid membrane was shown to possess the dramatic photobactericidal effect on Escherchia coli ( E. coli) under UV light illumination. Finally, introduction of TiO 2 nanoparticles on the actual commercial TFC membrane and application of RO field test after exposure to microbial cells verified a substantial prevention against the microbial fouling by showing less loss of RO permeability, offering a strong potential for possible use as a new type of anti-biofouling TFC membrane.

Coagulation mechanisms of iron salt and salicylic acid

This study focused on the reaction mechanisms exhibited by two iron coagulants and salicylic acid molecules. Experiments were performed to investigate the influence of polymeric and monomeric iron coagulants on treating waters containing natural analog organic matter. As predicted by the formation function theory, polyferric sulfate (PFS) consumed less alkali than FeCl3 during the coagulation process. This means that the PFS forms amorphous Fe(OH)3 colloid more easily than the FeCl3. On the other hand, when the pH value was less than 4, the Fe(III) ion could complex with the salicylic acid through coordination reaction. However, the complex compounds that formed from either PFS or FeCl3 under such conditions were too small to remove with filtration. At higher pH levels, iron-salt coagulates immediately reacted with OH− ion, forming amorphous Fe(OH)3 colloids and resulting in the adsorption of salicylic acid on Fe(OH)3 colloid surfaces. Because the –OH and –COOH functional groups of salicylic acid have complex-forming O-donors, they coordinated with Fe(OH)3 colloids on the surface layer of the oxide. Therefore, salicylic acid adsorbed on the surfaces of hydrous oxides through specific adsorption.

The role of surface functional groups in calcium phosphate nucleation on titanium foil: a self-assembled monolayer technique

Surface functional groups play important roles in nucleating calcium phosphate deposition on surgical titanium implants. In this study, various functional groups were introduced onto the surface of commercially pure titanium foils using a self-assembled monolayer (SAM) technique. An organic silane, 7-oct-1-enyltrichlorosilane (OETS) was used and OH, PO 4H 2, COOH groups were derived from its unsaturated double bond. Ti foils were first oxidized in concentrated H 2SO 4/H 2O 2. ESCA and contact angle measurements were used to characterize the SAM surfaces and confirm the presence of various functional groups. A fast calcium phosphate deposition experiment was carried out by mixing Ca 2+- and (PO 4) 3−-containing solutions in the presence of the surface-modified Ti samples at pH 7.4 at room temperature in order to verify the nucleating abilities of these functional groups. SEM, Raman spectroscopy, XRD and ATR-FTIR results showed that poorly crystallized hydroxyapatite (HA) can be deposited on the SAM surfaces with PO 4H 2 and –COOH functional groups, but not onto the SAM with –CHCH 2 and –OH. –PO 4H 2 exhibited a stronger nucleating ability than that of –COOH. The oxidized Ti sample also showed some calcium phosphate deposition but to a lesser extent as compared to SAM surfaces with –PO 4H 2 and –COOH. The pre-deposited HA can rapidly induce biomimetic apatite layer formation after immersion in 1.5 SBF for 18 h regardless of the amount of pre-deposited HA. The results suggested that the pre-deposition of HA onto these functionalized SAM surfaces might be an effective and fast way to prepare biomimetic apatite coatings on surgical implants.

Polymerization with TMA-protected polar vinyl comonomers. I. Catalyzed by group 4 metal complexes with ?5-type ligands

This paper describes the use of several kinds of group IV Cp based catalyst systems, in the synthesis of co- and terpolymers of ethylene, propylene and α-olefins endowed with OH and COOH functional groups. The hydroxy monomers used were 5-hexen-1-ol (4) and 10-undecen-1-ol (5) and the carboxy monomer was 10-undecen-1-oic acid (6). The three catalyst systems used were the C 2 symmetric ansa-zirconocene (1) the in-site titanium complex (2) and the non-rigid zirconocene (3), all activated by methylaluminoxane. Trimethylaluminium was used to protect the functional group of polar monomers. The first two catalyst systems suffer similar activity loss in the presence of polar monomer whereas the third one exhibited better tolerance toward the hydroxyolefins. NMR and FTIR spectroscopies were used to characterize the polymerization products. All three catalyst systems afforded functionalized co- and terpolymers by direct polymerization of ethylene/propylene/hydroxy-a-olefins but only the catalyst system (1)/MAO displays appreciable activities for direct polymerization of ethylene, propylene and carboxy-α-olefins.

Polymerization with TMA-protected polar vinyl comonomers. II. Catalyzed by nickel complexes containing ?-diimine-type ligands

α-Diimine Ni complexes (7, 8) were used as catalyst precursors with MAO in co- and terpolymerization of ethylene/propylene/α-olefins with OH and COOH functional groups. Trimethylaluminium was used to protect the functional group of polar monomers. The presence of 5-hexen-1-ol seems to have no effect on the polymerization rate at all for the N,N′-bis(2,6-diisopropylphenyl) derivative 8 but caused activity decreases of about fivefold in copolymerization and around two times in terpolymerization for the N,N-dimesityl derivative 7. The effect levels off at higher polar comonomer concentration. This system, (7)/MAO, also incorporates well both 10-undecen-1-ol and 10-undecen-1-oic acid. The activities obtained with these α-diimine Ni complexes in co- and terpolymerization are three to twenty times higher than those obtained with group 4 Cp based complexes especially at concentrations of polar monomer in the feed higher than 80 mM. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2471–2480, 1999

Production of short multi-walled carbon nanotubes

Multi-walled carbon nanotubes made by catalytic-pyrolysis of ethylene have curved bodies and exhibit entangled masses. Their average length is on the scale of microns, which is not suitable for carbon nanotubes to be used as a nanometer-scale material. Boiling carbon nanotubes in concentrated nitric acid or grinding in a ball mill can break the nanotubes. The average length of the nanotubes will be reduced and they will be relatively straight. In addition, on boiled carbon nanotubes, we find –OH, >CO and –COOH functional groups. In this state, the nanotubes can be dispersed evenly in a matrix when used to make a composite, which can result in an enhancement of the composite's properties, especially the mechanical properties.

Nanoporous alkoxy-derived titanium oxide coating: a reactive overlayer for functionalizing titanium surface.

Effective immobilization of bioactive substances such as adhesive proteins, synthetic peptides and growth factors on metallic substrates is required for a number of medical applications. In the present work, evidence is presented to show that an alkoxy-derived nano-porous titanium oxide coating, synthesized electrochemically on titanium in methanolic electrolytes, may act as an effective interface for functionalizing a titanium surface. It is demonstrated that nanoporous oxide coatings could facilitate fast diffusion of small organic molecules within the oxide network and form strong chemical bonds with the functional groups of these molecules at room temperature. Fourier transformed-infrared spectroscopy was used to investigate the nature of the interfacial interactions between the oxide network and a range of molecules containing COOH, OH, NH2, C=O and phosphoric acid functional groups. The results indicate that the nanometre-sized oxide clusters within the coating may play an essential role in effective immobilization of organic molecules by providing numerous binding sites for chemisorption of these species. The surface-derivatized oxide coating may provide a solid phase for the subsequent attachment of a broad range of biochemically active molecules on the titanium surface.

Chemical Force Microscopy

Chemical force microscopy (CFM) has been used to measure adhesion and friction forces between probe tips and substrates covalently modified with self-assembled monolayers (SAMs) that terminate in distinct functional groups. Probe tips have been modified with SAMs using a procedure that involves coating commercial Si3N4 cantilever/tip assemblies with a thin layer of polycrystalline Au followed by immersion in a solution of a functionalized thiol. This methodology provides a reproducible means for endowing the probe with different chemical functional groups.A force microscope has been used to characterize the adhesive interactions between probe tips and substrates that have been modified with SAMs which terminate with COOH and CH3 functional groups in ethanol water solvent. Force versus distance curves recorded under ethanol show that the interaction between COOH/COOH > CH3/CH3 > COOH/CH3. The measured adhesive forces were found to agree well with predictions of the Johnson, Kendall, and Roberts (JKR) theory of adhesive contact, and thus show that the observed adhesion forces correlate with the surface free energy

Spectroscopy of Aqueous Extracts of Forest Litter. I: Suitability of Methods

AbstractStructural characteristics of dissolved organic matter (DOM) have not been closely examined until recent analytical techniques became available. We examined the applicability of ultraviolet‐visible (UV‐VIS), Fourier‐transform infrared (FTIR), and electron spin resonance (ESR) spectroscopies using aqueous extracts of pine and broadleaf understory leaf litter. The ratio of UV‐VIS absorbances at 465 nm and 665 nm (E4/E6) were 7.8 to 8.5 for extracts of pine and 6.3 to 7.7 for the understory between pH 3.0 and 6.0. Using the standard method for humic substances (in 0.05 M NaHCO3 solution, pH 8.0), E4/E6 measurement produced varying results, and is not recommended for DOM. Well‐resolved FTIR spectra had features similar to those of humic substances; peak‐height ratios were used for semiquantitative analysis of DOM functional groups. Two FTIR sample‐preparation procedures were also compared: dried extracts on AgCl disks, and freeze‐dried DOM in KBr pressed pellets. The first allowed better analysis of COOH functional group deprotonation; the second preparation procedure produced spectra with identical absorbance ranges as those of AgCl disks, with similar peak‐height ratio trends as a function of pH, except for those associated with COOH/COO−. Contact between DOM and the salt in pressed pellets may have aided deprotonation of COOH, even at low pH. Interference from water occurred with KBr pressed pellets. Free radicals identified by ESR increased with pH, and shifts from 2.0036 to 2.0050 in ESR g values indicated that oxidation also increased with pH. We conclude that these spectroscopic techniques, modified from those developed for analysis of humic substances, are complementary and together provide useful information about the structure of the DOM of forest litter.

Chemical modification of capillary column for electrophoretic separations of transition metal ions

The surface modification of a fused-capillary for the separation of transition metal ions is described. A comparison was made of the properties of capillaries for each reaction stage, containing NH 2 , COOH and CONHOH functional groups, with those of the unreacted capillary by electroosmotic flow measurements and its dependence on pH. Multi-component mixtures of transition metal complexes with 4-(2-pyridylazo)resorcinol were separated in modified capillaries containing NH 2 and COOH functional groups with an ammonia-ammonium buffer of pH 9.0 at an applied voltage of 15 kV followed by direct UV-Vis detection at 520 nm. Others were separated using the treated capillary containing CONHOH groups with pH 4.0 imidazole (5 - α -hydroxy-isobutyric acid(8 M) as electrophoresis buffer, followed by indirect UV detection at 214 nm. The effects of electrophoretic buffer parameters on the complexation reaction and migration behaviour are discussed. Experimental results indicated that incorporating the chelating functional group in the inner wall of the capillary markedly enhances the selectivity of the system. Further, the optimum separation efficiencies were obtained by employing capillaries containing CONHOH functional groups.

Properties of electropolymerized polycarboxyphenylmethacrylamide matrices/graphite fiber composites: Crosslinking effect

AbstractImide formation from ‐CONH and ‐COOH functional groups of 2‐carboxyphenylmethacrylamide (2‐CPM), 4‐carboxyphenylmethacrylamide (4‐CPM), 4‐carboxyphenyl methacrylamide/methylmethacrylate (4‐CPM/MMA) and 4‐carboxyphenylmethacrylamide/N‐phenylmalemide (4‐CPM/NPMI) electropolymerized matrices was investigated. It was found that 2‐CPM polymers undergo intramolecular imidization and anhydride formation, which result in a small amount of crosslinked network. On the other hand, the thermally cured 4‐CPM polymer demonstrates a significant increase in gel fraction. Tg and dynamic storage modulus, owing to crosslinked network formation. Tgs of 4‐CPM/MMA and 4‐CPM/NPMI composites measured by thermomechanical analysis after thermal heating were increased and were correlated very well with the preheating time. The 4‐CPM/MMA composites with a particle crosslinking (Tg increased to 245°C) maintained a higher Izod impact strength than a typical epoxy composite (200 kJ/m2 vs. 100 kJ/m2). Upon heating to promote crosslinking, a lower shear strength (65 MPa) of a 4‐CPM/MMA composite increased to a strength of 78 MPa, close to the 80 MPa of an epoxy composite at 67% fiber volume fraction. A lower water absorption of around 1% was associated with the increased crosslinking. The mechanical properties of the 4‐CPM/NPMI composites showed a similar trend upon preheating.

KINETICS OF ALUMINUM AND SULFATE RELEASE FROM FOREST SOIL BY MONO- AND DIPROTIC ALIPHATIC ACIDS

A batch equilibration study evaluated the influence of naturally occurring low-molecular-weight mono- and diprotic aliphatic acids on the rate of Al and SO{sub 4}{sup 2{minus}} release in a Cecil soil (Typic Hapludult). The authors adjusted the pH of the organic acids (OAs) and of the soil suspension (3.8% w/w) to pH 4.0 and allowed them to equilibrate thermally before the experiment. After rapid addition of OAs to the soil suspension, they took solution samples at various time intervals and analyzed for Al, SO{sub 4}{sup 2{minus}}, and OA concentration. The initial concentration of OA in suspension was 1 {times} 10{sup {minus}5} mol liter{sup {minus}1}. Both Al and SO{sub 4}{sup 2{minus}} release followed pseudo-first-order kinetics, whereas OA adsorption obeyed simple first-order kinetics. The rate of Al release (k{sub 1}) was more rapid for the diprotic OA treatment (20.4 {times} 10{sup {minus}8} mol s{sup {minus}1}), as was SO{sub 4}{sup 2{minus}} release (1.63 {times} 10{sup {minus}8} mol s{sup {minus}1}), compared to the monoprotic OA treatment. The rate of Al release varied inversely with OA chain length and the distance between -COOH functional groups. The addition of substituent -OH groups between the -COOH groups further reduced K{sub 1}. A similar trend was observed for themore » rate of SO{sub 4}{sup 2{minus}} release (k{sub 1}) into solution. Monoprotic OAs were more rapidly adsorbed to the particle surfaces than were diprotic OAs. The authors postulate that removal of Al and SO{sub 4}{sup 2{minus}} from solution occurs via selective mineral precipitation.« less

Probing the influence of K 2CO 3- and Na 2CO 3-addition on the flash pyrolysis of a lignite and a bituminous coal with Curie-point pyrolysis techniques

The effect of K 2CO 3- or Na 2CO 3- addition on the composition of volatiles generated during the flash pyrolysis of a lignite and a medium-volatile bituminous coal was studied by means of analytical Curie-point pyrolysis mass spectrometry, g.c. and g.c.-m.s. At 358 °C no pyrolysis of the coal samples took place but there was desorption or evaporation of trapped components. Pyrolysis of the lignite occurred at a lower temperature than the medium-volatile bituminous coal, confirming that the bonds within the bituminous coal matrix are stronger as compared with the lignite. Alkali-carbonate addition suppressed the evolution of phenolic compounds originating from structures in the coal matrix with -OH and -COOH functional groups. No difference was observed between K 2CO 3 and Na 2CO 3. For the lignite the formation of o-methoxyphenol was not influenced by addition of alkali-carbonate because it is thought to derive from a structure in the lignitic coal matrix which does not contain an -OH functional group but is bonded within the coal matrix via an ether linkage. The phenolic compounds produced during flash pyrolysis of the medium-volatile bituminous coal are not reduced in abundance by the additives, indicating that this coal hardly contains hydroxyl functional groups and a major part of the oxygen is present in the form of ether linkages.

Micellar properties of quaternary ammonium surfactants bearing OH and COOH functional groups on their ionic heads

The micellar properties of the quaternary ammonium surfactants having the structures ▪ have been studied. It was found that although the presence of the OH group does not influence the micellar behavior with respect to the corresponding nonfunctionalized micelles, the presence of the ionizable COOH group induces important changes which may affect the catalytic activity of micelles and their use as models for enzymatic reactions.

SOME CHARACTERISTICS OF HUMIC MATERIALS IN CARIBBEAN VERTISOLS

A comparative investigation of the analytical features of organic matter fractions of acidic and calcium-saturated Vertisols (Ca-Vertisols) from the Caribbean was undertaken. The elemental composition and functional group content of the humic acids (HAs) and fulvic acids (FAs) were similar to previously reported values, except for the low yielding HAs of Ca-Vertisols which contained a greater proportion of O (35.82–47.17%). In addition, high values (8.38 meq/g–11.71 meq/g) for the COOH functional groups of the FAs emphasized the inherent high reactivity of the humic materials. Spectrophotometric analysis supported the view arrived at through chemical analysis that metal-organic (FA) complexes of Vertisols contained Al, Fe and Si with more soluble complexes in the Ca-Vertisols and in the presence of a basic cation (Ca). DTA analysis indicated that the organo-mineral complexes of Vertisols were regular and thermostable. Key words: Vertisols, humic materials, functional groups, infrared, DTA

Acid functional group content of aquatic humic matter: Its dependence upon origin, molecular weight and degree of humification of the material

Abstract The acididic functional group content was investigated of molecular weight fractions of fulvic and humic acids sampled at various locations of a watershed within the Laurentide provincial park, Quebec. In order to study the effect of humification, also humic material produced by a streptomycete culture and sampled at regular intervals during a 6 months’ incubation period was investigated. The equivalent weights and the number of COOH and phenolic OH functional groups measured on the fulvic and humic acid molecular weight fractions were compared with data reported for humic material from other aquatic and terrestrial environments. Also investigated were seasonal and environmental effects on the equivalent weights and the COOH and phenolic functional group values as well as the influence of humification on these parameters. It was shown that although aquatic humic compounds have several properties in which they are quite distinct from soil humus, in their acidic functional groups aquatic humic comp...

Gel Filtration Studies of Trace Metal‐Fulvic Acid Solutions Extracted From Sewage Sludges

AbstractTrace metal‐fulvic acid solutions extracted with NaOH from two chemically different sewage sludges and separated from humic acid using HCl were fractionated on a column of Sephadex G‐10 gel using deionized water at pH 5.65 as the eluant. The effluent from the gel was analyzed in 3‐ml increments for organic C, Cl, and the metals Cd, Cu, Fe, Ni, and Zn. Elution diagrams prepared with the analytical data showed multiple maxima in organic C concentration and a single maximum in Cl concentration (indicating the presence of inorganic salts). Fe and Cu showed concentration maxima that followed closely those in both the organic and inorganic fractions, while Cd, Ni, and Zn tended to show maxima following the inorganic fraction peak and only one or two of the organic C maxima. The data indicated that Cu and Fe formed complexes with sludge‐derived fulvic acid (FA) under the conditions of the experiment. Cd, Ni, and Zn were associated with the FA only weakly, in a manner dependent on the nature of the sludge, and in the relative order of affinity Zn > Ni > Cd. These data suggested that sludge‐derived FA behaves toward trace metals as a relatively harder Lewis base than Cl−.Infrared spectra of the eluted organic fractions indicated that protein decomposition products and polysaccharide components appear in the fractions of relatively larger molecular size, as do the components containing SO3H groups. The IR spectra also gave evidence that COOH and SO3H functional groups are involved in metal‐FA interactions. An important organic fraction of sludge‐derived FA was identified that appears to be an aliphatic, carboxylic acid mixture which can complex only Cu significantly.