Amine Modifiers Research Articles

Multifunctional Amine Modifiers for Selective Dehydration of Methyl Lactate to Acrylates.

Dehydration of methyl lactate to acrylic acid and methyl acrylate was experimentally evaluated over a Na-FAU zeolite catalyst impregnated with multifunctional diamines. 1,2-Bis(4-pyridyl)ethane (12BPE) and 4,4'-trimethylenedipyridine (44TMDP), at a nominal loading of 40 wt % or two molecules per Na-FAU supercage, afforded a dehydration selectivity of 96 ± 3% over 2000 min time on stream. Although 12BPE and 44TMDP have van der Waals diameters approximately 90% of the Na-FAU window opening diameter, both flexible diamines interact with internal active sites of Na-FAU as characterized by infrared spectroscopy. During continuous reaction at 300 °C, the amine loadings in Na-FAU remained constant for 12BPE but decreased as much as 83% for 44TMDP. Tuning the weighted hourly space velocity (WHSV) from 0.9 to 0.2 h-1 afforded a yield as high as 92% at a selectivity of 96% with 44TMDP impregnated Na-FAU, resulting in the highest yield reported to date.

Engineering Surface Amine Modifiers of Ultrasmall Gold Nanoparticles Supported on Reduced Graphene Oxide for Improved Electrochemical CO2 Reduction

AbstractUltrasmall gold (Au) nanoparticles with high mass activity have great potential for practical applications in CO2 electroreduction. However, these nanoparticles often suffer from poor product selectivity since their abundant low‐coordinated sites are favorable for H2 evolution. In this work, a catalyst, reduced graphene oxide supported ultrasmall Au nanoparticles (≈2.4 nm) is developed which delivers high Au‐specific mass activities (>100 A g−1) and good Faradaic efficiencies (32–60%) for the CO2‐to‐CO conversion at moderate overpotentials (450–600 mV). The efficiencies can be improved to 59–75% while retaining the ultrahigh mass activities via a simple amine‐modification strategy. In addition, an amine‐structure‐dependent effect is revealed: linear amines promote the CO formation whereas the branched polyamine greatly depresses it; the increasing alkyl chain length boosts the promotion effect of linear amines. The strong Au‐amine interaction and molecular configuration induced amine coverage on the ultrasmall Au NPs may contribute to this effect.

Amine-graphene oxide/waterborne polyurethane nanocomposites: effects of different amine modifiers on physical properties

To study the dispersity of different amine-graphene oxide (amine-GO) in polymer matrix and the interfacial interactions between functionalized graphene oxide and matrix, two kinds of modifiers—organoamine- and aminosilane-coupling agents—were used to functionalize graphene nanosheets to obtain functionalized graphene oxide/waterborne polyurethane nanocomposites by in situ polymerization. The chemical structure, morphology, and interlayer space of amine-GO nanoplatelets were confirmed by FT-IR, Raman, TGA, XPS, TEM, AFM, and XRD. The dispersity behaviors between different amine-GOs and polymers were evaluated by FESEM. The thermal, mechanical, and hydrophobic properties of the nanocomposites were investigated by TGA, tensile testing machine, and water contact angle test, respectively. It was found that the tensile strength of nanocomposites was increased from 10.13 to 27.79 and 28.96 Mpa after the addition of amine-GO functionalized by APTMS and APTES, respectively. The better thermal stability and hydrophobicity of nanocomposites were also achieved by the addition of amine-GO, especially those modified by aminosilane-coupling agents. This study paves a new route for designing and developing chemically converted graphene oxide nanosheets/polymer nanocomposite materials by altering suitable amine-modifier to functionalize graphene oxide nanosheets and then optimizing the interphases between graphene oxide nanosheets and polymer matrices.

Influence of polar modifiers on microstructure of polybutadiene obtained by anionic polymerization. Part 3: Lewis acid alkoxide (μ) and Lewis base amine, amine-ether, and ether mixed-type (σ+μ) polar modifiers

ABSTRACTThe influence of mixtures of sodium mentholate (SMT) as a Lewis acid polar modifier and different Lewis base polar modifiers (amines, amine-ethers, ethers) on the microstructure of polybutadiene obtained by anionic polymerization was studied and compared to the influence of the same polar modifiers used separately. Detailed characterization of the polybutadienes in terms of the content and distribution of butadiene isomeric repeating units was performed by 13C NMR and supported by FT-IR-ATR and 1H NMR data analysis. The results obtained indicated that the use of a mixture of Lewis acid and Lewis base in most cases enhanced formation of 1,2 butadiene structures in comparison to the Lewis bases used separately. However, application of a mixture of SMT and DTP resulted in lower vinyl content than when DTP was applied alone. It is worthwhile to note that the combination of a Lewis acid (SMT) and one of Lewis bases tested (DMEAEE) enabled obtaining very high vinyl polybutadiene (88% 1H NMR, 96% 13C NMR).

Preparation and Characterization of Amine-Modified Maleated Polypropylene

In this study, reactive processing of maleated polypropylene with different types of amine modifiers, including 1,12-diaminododecane, tetraethylenepentamine, p-phenylenediamine, and 1,6-diaminlhexane were carried out. The changes in melt viscosity, molecular weight and its distribution, as well as crystallization were measured and discussed. All the modified samples exhibited increased molecular weight and enhanced branching structure compared to the virgin maleated PP. Aniline modified sample exhibited the highest weight average molar mass., while polyamide-modified maleated PP showed the highest degree of branching. It was also noted that all of the amine-modified samples showed higher crystallization and melting temperatures than that of the unmodified sample.

Network structure and thermomechanical properties of hybrid DGEBA networks cured with 1‐methylimidazole and hyperbranched poly(ethyleneimine)s

AbstractThe use of commercially available hyperbranched poly(ethyleneimine)s (Lupasol™, BASF) as polymeric modifiers in diglycidyl ether of bisphenol A thermosetting formulations using 1‐methylimidazole (MI) as anionic initiator has been studied. Poly(ethyleneimine)s can get incorporated into the network structure by condensation of amine and epoxy groups. The excess, over‐stoichiometric epoxy groups can undergo anionic homopolymerization initiated by MI. The thermal, dynamomechanical, and mechanical properties of the resulting materials have been determined using DSC, thermomechanical analysis (TMA), dynamomechanical analysis (DMA), and mechanical testing. The effect of the different amine modifiers on the MI networks, determined by their structure, is complex. Low initiator content and high molecular weight modifiers create significant mobility restrictions, which have a strong effect on the glass transition temperature and the apparent crosslinking density of the cured materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Investigation of tensile properties and dyeing behavior of various polypropylene/amine modifier blends

AbstractPolypropylene is utilized in manifold applications due to its unique properties. However, its use has been limited in the textile industry because conventional dyestuffs have no affinity for this polymer. Amine modifiers, generally improve the dye‐ability of polypropylene. Polyamide 6 (PA6) is a traditional amine modifier which improves the dyeing ability of polypropylene with disperse dyes. In this investigation, polyetheramine (PEA) is introduced as a novel amine modifier which improves the dye‐ability of polypropylene with disperse and acid dyestuffs. To this end, the dyeing behavior as well as possible impairments of tensile properties of PEA modified polypropylene were studied and compared to PA6 modified polypropylene. As with the PA6 containing blends, the tensile properties of the incompatible PP/PEA blends decreased due to weak interfacial adhesions between the components of the blends. However, the incorporation of a compatibilizer into such blends led to better dispersions of modifiers in the matrix as well as formation of amide or imide linkages which in turn reincreased the tensile properties almost to their initial values. Both PEA and PA6 modifiers improved the disperse dye uptake of the blends. However, Only Jeffamine ED‐2003 (i.e., PEA) was capable of enhance the acid dye uptake of modified polypropylene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Rapid HPLC Method for Determination of Parachloroaniline in Chlorhexidine Antiseptic Agent in Mouthrinses, Ophthalmic and Skin Solution

We described a simple and rapid method to quantify simultaneously chlorhexidine (CHD) and its major metabolite, para Chloroaniline (pCA) by HPLC with UV detection without the additional need of mobile-phase amine modifiers or ion-pairing reagents, with good resolution between pCA and CHD, symmetry peak of the compound and short run time. HPLC-UV analyses were performed using a Dionex® Summit liquid chromatograph (Dionex Corp, Sunnyvale, CA, USA). Chromatographic separations were carried out on a Luna® 150 mm×3 mm i.d. column packed with 3 µm CN (cyano) particles (Phenomenex®), guarded by an on-line filter. Mobile phase consist of methanol:water with sodium chloride with 0.02% of formic acid (55:45). Wavelengths for pCA and for CHD are 238 and 255 nm respectively. Influence of methanol and of sodium chloride content in the eluant has been studied. Linearity of CHD is very good, from 0.5 up to 21.2 µg/l while linearity of pCA is in the range of 0.05 to 10 µg/l with correlation coefficients above 0.999. Resolution between the components is above 4, asymmetry is about 1.3 and 1.7 for pCA and CHD respectively and the run time is less than 5 minutes. This method has been applied to CHD solution of different medical devices. No interference has been reported, and the analysis of direct injection of solution, without any treatment is achieved in less than five minutes.In conclusion, we present a validated method for dosage of CHD and its major impurity pCA, known to be carcinogen, available into medical products or medicinal device for in-vitro diagnostic.

Novel ultra stable silica-based stationary phases for reversed phase liquid chromatography—Study of a hydrophobically assisted weak acid cation exchange phase

A mixed-mode reversed-phase/weak cation exchange (RP/WCX) phase has been developed by introducing a small amount of carboxylate functionality into a hydrophobic hyper-crosslinked (HC) platform. This silica-based HC platform was designed to form an extensive polystyrene network completely confined to the particle's surface. The fully connected polymer network prevents the loss of bonded phase, which leads to superior hydrolytic stability of the new phase when compared to conventional silica-based phases. Compared to previously introduced HC phases the added carboxylic groups impart a new weak cation exchange selectivity to the base hydrophobic HC platform. The phase thus prepared shows a mixed-mode retention mechanism, allowing for both neutral organic compounds and bases of a wide polarity range to be simultaneously separated on the same phase under the same conditions. In addition, the new phase offers the flexibility that gradients in organic modifier, pH or ionic competitors can be used to affect the separation of a wide range of solutes. Moreover, the inherent weak acid cation exchange groups allow formic and acetic acid buffers to be used as eluents thereby avoiding the mass spectrometric ionization suppression problems concomitant to the use of non-volatile additives such as strong amine modifiers (e.g. triethylamine) or salts (e.g. NaCl) to elute basic solutes from the strong cation exchange phase which was previously developed in this lab. The use of the new phase for achieving strong retention of rather hydrophilic neurotransmitters and drugs of abuse without the need for ion pairing agents is demonstrated.

Hydroxyalkyl derivatives of phenyldiamine as modifiers for unsaturated polyester resins, Part 1: Derivatives of phenyl‐1,4‐diamine

AbstractThe results are presented on the synthesis of new modifiers and functioning of amine modifiers for unsaturated polyester resins, obtained by reacting ethylene oxide or propylene oxide with phenyl‐1,4‐diamine. Also the effect of the modifiers and cobalt accelerator on the reactivity of resins was studied. When used in the amount of up to 2 wt %, the amines substantially (several times) reduced the gelation time of modified unsaturated polyesters. The reactivity of resins, however, improved in expense of their stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Alternative Synthetic Routes to Epoxy Polymer – Clay Nanocomposites using Organic or Mixed‐Ion Clays Modified by Protonated Di/Triamines (Jeffamines)

AbstractThe use of homoionic organic clays and mixed‐ion organic/inorganic clays modified by di‐ or triamines (Jeffamines), which are being used as epoxy resin curing agents, in the synthesis of polymer nanocomposites has been studied in this work. Our aim is to enhance polymer crosslinking and interfacial adhesion in the nanocomposite structure by utilizing the functionality of the di/triamines on the surface of clay nanolayers and by reducing the organic modifier via formation of homostructured mixed‐ion organic/inorganic clays. The results show that the use of homoionic organic clays exchanged with relatively short chain di‐ or triamines and mixed‐ion organic/inorganic clays partially exchanged (ca. 35%) with long chain diamines resulted in intercalated structures with enhanced thermo‐mechanical properties (Young's Modulus, Storage Modulus). On the other hand, homoionic organic clays exchanged with long chain diamines and triamines resulted in exfoliated nanocomposites but with compromised mechanical properties due to the plasticizing effect of the long chain amine modifiers.

Amine Modifiers with an s‐Triazine Ring for Unsaturated Polyester Resins, 2

AbstractThe paper deals with the synthesis of amine modifiers for unsaturated polyester resins obtained from N‐phenyl‐2‐amineethanol and 2,4‐dichloro‐6‐methoxy‐1,3,5‐triazine (modifier A), 2‐chloro‐4,6‐dimethoxy‐1,3,5‐triazine (modifier B) or with cyanuric chloride (modifier C). Properties of amine modifiers for unsaturated polyester resins are presented. The modifiers were incorporated into resins at the polycondensation stage.magnified image

Selective Hydrogenation of p-Chloronitrobenzene over Ru–Ir/γ-Al2O3 Catalyst Modified by Organic Amines

Abstract A Ru–Ir/γ-Al2O3 bimetallic catalyst was prepared by impregnating γ-Al2O3 with an isopropylalcohol solution of RuCl3 and H2IrCl6. The effect of organic amine modifiers on the selective hydrogenation of p-chloronitrobenzene (p-CNB) over Ru–Ir/γ-Al2O3 was investigated. The addition of ethylenediamine and L-lysine remarkably improved the catalytic activity of Ru–Ir/γ-Al2O3 and the selectivity for p-chloroaniline (p-CAN) at high conversion of p-CNB. In the presence of ethylenediamine, the conversion of p-CNB increased from 37.2% to 95.6% and the selectivity for p-CAN was maintained at 100%. Similarly, the addition of L-lysine greatly enhanced the activity of the catalyst and completely suppressed the formation of by-products. The promotion effect was attributed to the coordination of ethylenediamine or L-lysine with the metal center, which improved the cooperation between ruthenium and iridium.

Amine Modifiers with an s‐Triazine Ring for Unsaturated Polyester Resins, 1

AbstractSummary: Synthesis and properties of amine modifiers for unsaturated polyester resins are presented. The modifiers were obtained by reacting 3‐azapentan‐1,5‐diol (diethanoloamine) with 2,4‐dichloro‐6‐methoxy‐1,3,5‐triazine, 2‐chloro‐4,6‐dimethoxy‐1,3,5‐triazine or with cyanuric chloride. They were incorporated into the structure of typical unsaturated polyester resins in the polycondensation stage, i.e. prior to dilution with styrene, in the amount of 0.25 through to 2.0 wt.‐%. The effect of the modifier presence on the curing behavior of the resulting resins is discussed.Gelation times for unsaturated polyester resins modified with modifiers A, B, and C are shown with the curing system consisting of peroxide initiator and (▪): 0.10 cm3, (•): 0.15 cm3, (▴): 0.25 cm3, and (▾): 0.50 cm3 of cobalt(II) octenate solution per 25 g of resin.imageGelation times for unsaturated polyester resins modified with modifiers A, B, and C are shown with the curing system consisting of peroxide initiator and (▪): 0.10 cm3, (•): 0.15 cm3, (▴): 0.25 cm3, and (▾): 0.50 cm3 of cobalt(II) octenate solution per 25 g of resin.

LC Determination of Ritonavir, a HIV Protease Inhibitor, in Soft Gelatin Capsules

A rapid, simple and sensitive high-performance liquid chromatographic method (HPLC) has been developed to assay ritonavir in semisolid capsules. The HPLC analysis used a reversed-phase C8 (125 × 4.0 mm i.d., 5 μm particle size) analytical column and a mobile phase consisting of methanol and water (67:33, v/v), with UV detection at 210 nm. Specificity was evaluated using a photodiode array detector (PDA). The validation data showed that the assay is sensitive, specific and reproducible for determination of ritonavir in this dosage form. Calibration curves were linear from 100–300 μm L−1 (R2 ≥ 0.999). The accuracy of the method ranged from 98.8 to 102.0%. Mean inter- and intra-assay relative standard deviations (RSD) were less than 1.0%. The proposed method provided an accurate and precise analysis of ritonavir in soft capsules, requiring neither the use of a buffered mobile phase, nor the addition of amine modifiers.

Synthetic Modifiers for Platinum in the Enantioselective Hydrogenation of Ketopantolactone: A Test for the Mechanistic Models of Ketone Hydrogenation

Various derivatives of (R)-1-(1-naphthyl)-ethylamine have been synthesized and tested as chiral modifiers of Pt/alumina in the enantioselective hydrogenation of ketopantolactone. The best modifiers (ee up to 79%) possess an ester function in the α-position to the amino group. The modifiers performed far better in AcOH than in toluene, indicating that protonation of the N atom is important in enantioselection. The striking non-linear behaviour of modifier mixtures with cinchonine indicates that the alkaloid adsorbs much stronger on Pt than the naphthylethyl-amine derivatives. Two mechanistic models are proposed for interpretation of the results, involving an N-H-O or N + -H-O bond between the amine-type modifier and the keto carbonyl O atom of ketopantolactone, in apolar and protic media, respectively. In both cases the H atom originates from the modifier and not from the substrate (half-hydrogenated-state). The higher ee achieved in acidic medium is attributed to the better proton donor ability of the protonated amine modifiers. The models are applicable also to the hydrogenation of ethyl pyruvate.

Studies on activity of s-triazine ring containing amine modifiers in curing of unsaturated polyester resins

Summary — The results of the study on the activity of amine modifiers for unsaturated polyester resins obtained by reaction of diethanolamine (3-azapentane-1,5-diol) a nd N-phenyl-2-aminoethanol with 2,4-dichloro-6-methoxy-1,3,5-triazine, 2-chloro-4,6-dimethoxy-1,3,5-triazine or with cyanuric chloride are presented. Effects of the type and amount of amine modifier as well as cobalt accelerator on gelation time and stability of the resins were investigated.

Separation of low-molecular mass peptides by capillary electrophoresis with the use of alkylamines as dynamic coating agents at low pH

Modification of the silanophilic activity of the inner surface of the capillary wall was studied in a capillary electrophoretic system using alkylamines containing background electrolytes at acid pH. The effect of the following amine additives was investigated: (1) alkyl-α,ω-diamines (1,2-diaminoethane, 1,4-diaminobutane, 1,7-diaminoheptane, spermine), (2) polymeric amines (polyethylenimine, polybrene), (3) cationic amine surfactants (cetrimide, hexamethonium bromide). A seven membered test mixture of peptides (Gly–Pro–Ala, Pro–hPro, Gly–Pro–Arg, Gly–Pro–Gln, Lys–Pro–Gly, Asn–Pro–Gly, His–Pro–Gly) possessing one or more amino groups was used for selectivity evaluation. Under optimised concentration of the amine modifiers the selectivity was always improved (except for polybrene), particularly with the fast moving analytes. The best results were obtained with 1,2-diaminoethane and 1,7-diaminoheptane. On the other hand with slowly moving peaks the best separations were obtained with 1,7-diaminoheptane, hexadecyltrimethylammonium bromide and hexamethonium bromide, i.e. with modifiers possessing large aliphatic domains which are likely to be hydrophobically bonded with the separated solutes. The selectivity improvement with fast moving members of the test mixture can be ascribed to the decrease of the electroosmotic flow, while the improved separation with slowly moving peaks appears to reflect the altered interaction with the hydrophobized capillary wall. As expected the endoosmotic flow was in all cases decreased. The practical applicability of using amine based dynamic modifiers of the capillary wall was demonstrated on a natural peptide mixture (bacterial collagenase hydrolysate of collagen types I and III).

Polyimide/montmorillonite nanocomposites based on thermally stable, rigid-rod aromatic amine modifiers

The preparation and processing of most of polymer/clay nanocomposites need high temperature. This limited the application of commonly used organic modifiers of long carbon-chain alkyl ammonium salts because of their low thermal stability. In this study, we synthesized two novel thermally stable, rigid-rod aromatic amines. Montmorillonite (MMT) treated by these amines exhibited larger layer-to-layer spacing, higher thermal stability than that treated by commonly used 1-hexadecylamine and also high ion-exchange ratio (>95%). They were applied to prepare nanocomposites with polyimide (PI) by in situ polymerization. XRD, TEM were used to obtain the information on morphological structure of PI/MMT nanocomposites. DMA, TGA, DSC, universal tester were applied to characterize the mechanical and thermal properties of the nanocomposites. When the MMT content was below 3wt%, the PI/MMT nanocomposites were strengthened and toughened at the same time. The introduction of a small amount of MMT also led to improvement in thermal stability, slight increase in glass transition temperature, marked decrease in coefficient of thermal expansion and decrease in solvent uptake. MMT treated by these aromatic amines exhibited better dispersibility and (probably) interfacial interaction with PI matrix than that treated by 1-hexadecylamine. The nanocomposites based on these MMT resultantly exhibited better mechanical, thermal and solvent resistance properties than those based on 1-hexadecylamine treated MMT.

Methodology for quantifying residues of chlorhexidine in raw dairy milk.

A residue method was developed as part of a pharmacokinetics study to determine the elimination of chlorhexidine in raw milk after intramammary infusion into dairy cows affected with bovine mastitis. The developed liquid/liquid and solid-phase extraction procedures effectively reduced sources of milk product interferences in the final extract. By optimizing mobile-phase pH buffer/acetonitrile gradient conditions and employing an end-capped reverse-phase polar embedded-phase chromatographic column, excellent peak resolution was achieved without the additional need of mobile-phase amine modifiers or ion-pairing reagents. The combined cleanup and chromatographic method steps reported herein were sensitive and reliable for determining the pharmacokinetic elimination of chlorhexidine following intramammary infusion. The residue method was found to be rugged with a lower detection limit of 0.1 ppm.