Siloxanes with 1-oxypyridin-3-yl groups. Part 6. synthesis of copolymers and application as transacylation catalysts

Linear end-blocked and crosslinked siloxane copolymers containing dimethylsiloxyl and methyl(1-oxypyridin-3-yl)siloxyl groups were prepared and characterized thermally (TGA) and spectroscopically. These hydrophobic copolymers were found to be highly effective transacylation catalysts in the synthesis of carboxylic anhydrides and the hydrolysis of diphenyl phosphoro-chloridate (DPPC) under phase-transfer catalysis (PTC) conditions, i.e. CH₂Cl₂-H₂O suspension. The insolubility of the copolymers in water and the preference of the intermediate, polymeric 1-acyloxypyridinium ion for the more lipophilic carboxylate ion in anhydride formation suggest that the reaction occurs at the CH₂Cl₂-H₂O interphase. The rapid rate of hydrolysis of DPPC under PTC conditions and in water provides evidence for initial hydrophobic binding or association of the hydrophobic catalyst prior to reaction with a water-insoluble substrate.     

Synthesis of Nano‐γ‐Ferric Oxide by Thermolysis of the 2‐Mercapto‐5‐Methylpyridine‐N‐Oxide‐Iron(III) Complex via Factorial Design

2‐Mercapto‐5‐methylpyridine‐N‐oxide (MMPNO) and its sodium salt (NaMMPNO) were synthesized. The reaction of the latter with Fe³⁺ generates Fe(MMPNO)₃ chelate. The thermolysis of this chelate at 350 °C yielded highly pure reddish‐brown γ‐Fe₂O₃ nanocrystallites with an average particle size of 6.2 nm, a particle size range of 4.2 to 14.8 nm, and a specific surface area of 51.5 m²g^–1. The thermolysis process was optimized using the 2² fractional design. Quantitative tests and characterization of products were carried out by UV‐vis spectroscopy, XRD, LLS, SEM, TGA, BET, TEM, FT‐IR, elemental microanalysis, and classical analytical measurements.     

Heterobimetallorganische 1,2‐(N,N‐Dimethylaminomethyl)ferrocenyl‐Derivate des vier‐ und zweiwertigen Zinns: Synthesen,Charakteristika und Kristallstrukturen

SnCl₄ reacts with [1,2‐(N,N‐dimethylaminomethyl) ferrocenyl]lithium (FcNLi) under formation of the organo tin compounds of the four valued tin (FcN)_n SnCl _4‐n [n = 1( 1 ), 2( 2 ), 3( 3 ), 4( 4 )]. The heterobimetallic chelate complex bis[1,2‐(N,N‐dimethylaminomethyl)ferrocenyl]tin(II) (FcN)₂ Sn ( 5 ) is formed at the reaction of SnCl₂ with two equivalents of FcNLi. The heterobimetallic tin compounds 1 — 5 were characterized by ¹H NMR‐, ¹³C‐NMR and mass spectroscopy, single crystal x‐ray analyses ( 1,3,4,5 ), ⁵⁷ Fe‐Moessbauer spectroscopy ( 1, 3, 4, 5 ), respectively cyclic voltammetry.     

Studies on the preparation and properties of conductive polymers. V. Analysis of metallized polyamide complex metal chelate films and precipitates in metal chelate solution

Metallized films were obtained by the reduction of polyamide metal chelate films with reducing agents. In the preparation of polyamide metal chelate solution, a small amount of precipitate forms when a certain stoichiometric ratio of formic acid, polyamide, and metal salts was mixed. The precipitate formation rate was affected by kinds and concentrations of metal salts, kinds and molecular weight of polyamide, and solution temperature. In addition, the precipitate formation rate affects the conducting surface metallic substance of reduced nylon/CuCl₂/NiCl₂ complex metal chelate film. The conducting surface is metallic Ni for low-molecular-weight nylon 4/CuCl₂/NiCl₂ film and metallic Cu for high-molecular-weight nylon 4/CuCl₂/NiCl₂ film reduced by NaBH₄ aqueous solution. The precipitate consists of polyamide, metal salt, and formic acid. The interaction among the polyamide, metal salt, and formic acid appears to be by means of hydrogen bonds and ionic bonds. The proposed structure of precipitate was also studied. © 1992 John Wiley & Sons, Inc.     

Four novel lanthanide(III) coordination polymers with 3D network structures containing 2-fold interpenetration

Four novel lanthanide(III) coordination polymers [Ln(L)_1.5(H₂O)₂]·5H₂O [Ln = Sm (1), Eu (2), Tb (3), Dy (4)] have been hydrothermally synthesized by the reaction of 1,2-bis[4-amino-5-carboxylmethylthio-(1,2,4-triazol-3-yl)]ethane (H₂L) with lanthanide(III) salts, and structurally characterized by single crystal X-ray diffraction. Polymers 1–4 are isostructural, in which all the Ln^III atoms are nine-coordinated and the carboxylate groups adopt three different coordination modes (bidentate chelate, bidentate bridging, bidentate chelate bridging) to connect Ln^III atoms. These polymers exhibit 3D network structures with 2-fold interpenetration, in which intriguing 1D channels are observed. Besides, the spectra properties of the title polymers are investigated, the strong luminescence characteristics of 2–3 are found.     

Hydrophobic and tribological behaviors of a poly(p‐phenylene benzobisoxazole) fabric composite reinforced with nano‐TiO2

1H,1H,2H,2H‐Perfluorooctyl trichlorosilane (PFTS) was used to modify TiO₂ nanoparticles, and hydrophobic PFTS–TiO₂ nanoparticles were obtained by an ultrasonic reaction method. The PFTS–TiO₂ surface morphological and hydrophobic properties were analyzed with scanning electron microscopy (SEM), Fourier transform infrared spectrometry, and contact angle (CA) testing. Then, the poly(p‐phenylene benzobisoxazole) fabric–phenolic composite filled with PFTS–TiO₂ as a lubricant additive was fabricated by a dip‐coating process. The tribological properties of the composite were investigated, and the wear surface morphology was observed by SEM. The experimental results show that the water CA of the composite filled with PFTS–TiO₂ was 158°, and the composite containing 4 wt % PFTS–TiO₂ exhibited excellent antifriction and abrasion resistance. The hydrophobic surface of the composite showed excellent durable performance with a static water CA of 126.7° after abrasion. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45077.     

Studies on the preparation and properties of conductive polymers. IV. Novel method to prepare metallized plastics from metal chelates of polymides–imides

A new type of polyamide–imides (PAI) was synthesized by direct polycondensation. A series of polyamide–imide metal chelate films was prepared by the transition-metal salts (AgNO₃, CuCl₂, and CoCl₂) mixed with the polyamide–imides in NMP solution. These polyamide–imide metal chelate films were reduced by various reducing agents, and the reduced films exhibited low surface resistivity around 10⁰?10¹ Ω/cm². The surfaces of these conductive films were proved to be metallized by means of X-ray analysis. The metal adhered on the film was believed to be responsible for the improvement of electrical conductivity. The effects of kinds and concentrations of metal salts, kinds and concentrations of reducing agents, and reduction time on the conductivity of metallized films were investigated. The IR spectra and SEM observations of unreduced and reduced polymer chelate films were also studied.     

Synthesis of Salicylic Acid-Polystyrene Type Chelate Resin with a New Route

A new route to synthesize salicylic acid-polystyrene type chelate resin is developed. In the presence of Lewis acid catalyst SnCl₄, the chloromethylation reaction of crosslinked polystyrene microspheres (CPS) was first performed using 1,4-bis(chloromethoxy)butane which is un-carcinogenic as a chloromethylation reagent, and the chloromethylated crosslinked polystyrene microspheres (CMCPS) were obtained. Subsequently, the nucleophilic substitution reaction between the benzyl chloride groups on CMCPS microspheres and 5-amino salicylic acid (ASA) was conducted, and chelate resin ASA-CPS was successfully obtained. The effects of main factors on the nucleophilic substitution reaction were examined. The chelating property of the prepared ASA-CPS resin for Fe³⁺ ion was tested preliminarily. The experimental results show that the reaction rate of the nucleophilic substitution reaction between the benzyl chloride groups on CMCPS microspheres and ASA is independent of the concentration of the nucleophilic reagent ASA. Therefore, the reaction is a typical unimolecular substitution reaction, namely, the substitution reaction has a mechanism of S_N1. The solvent with stronger polarity is advantageous to the fracture of C-Cl bond of the benzyl chloride groups, so the polarity of the solvent influences the substitution reaction rate greatly. To increase the reaction temperature also makes for the substitution reaction. The ASA-CPS resin possesses very strong chelating ability towards Fe³⁺ ions by right of the synergism of chelation and electrostatic interaction., and the adsorption capacity can get up to 21 g/100 g.     

Preparation of hydrophobic SiO<Subscript>2</Subscript>@(TiO<Subscript>2</Subscript>/MoS<Subscript>2</Subscript>) composite film and its self-cleaning properties

TiO₂/MoS₂ composite was encapsulated by hydrophobic SiO₂ nanoparticles using a sol–gel hydrothermal method with methyltriethoxysilane (MTES), titanium tetrachloride (TiCl₄), and molybdenum disulfide (MoS₂) as raw materials. Then, a novel dual functional composite film with hydrophobicity and photocatalytic activity was fabricated on a glass substrates via the combination of polydimethylsiloxane adhesives and hydrophobic SiO₂@(TiO₂/MoS₂) composite particles. The influence of the mole ratios of MTES to TiO₂/MoS₂ (M:T) on the wettability and photocatalytic activity of the composite film was discussed. The surface morphology, chemical compositions, and hydrophobicity of the composite film on the glass substrate were investigated by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle (water CA) measurements. The results indicated that the composite film exhibited stable superhydrophobicity and excellent photocatalytic activity for degradation of methyl orange (MO) even after five continuous cycles of photocatalytic reaction when M/T was 7:1. The water CA and degradation efficiency for MO remained at 154° and 94%, respectively. Further, the composite film showed a good non-sticking characteristic with the water sliding angle (SA) at about 4°. The SiO₂@(TiO₂/MoS₂) composite consisting of hydrophobic SiO₂ nanoparticles and TiO₂/MoS₂ heterostructure could provide synergistic effects for maintaining long-term self-cleaning performance.     

Dispersion and interaction of ZrB2 nanopowders with gallic acid in n-butanol

This paper has systematically investigated the dispersion behavior of ZrB₂ nanopowders in n-butanol solution and the adsorption mechanism of gallic acid on ZrB₂. Gallic acid was found to be effective as a dispersant, which could provide stabilization of ZrB₂ particles in the suspension. The stability of ZrB₂ suspension and the adsorption amount of gallic acid were increased with increasing of gallic acid content (up to 6 wt%), and the pH value did not need to be adjusted. The results of Fourier transform infrared spectroscopy (FTIR) measurement and computer simulation revealed that the adsorption of gallic acid involved the interaction of two adjacent OH groups with Zr ions on the particle surfaces and complexation, which formed mononuclear chelate through a Zr atom binding to O atoms at position 3 and 4, or binuclear chelate by two Zr atoms replacing H atoms at position 4 and 5.     

Novel amphiphilic carbon black composite nanoparticles from TEMPO-terminated polymer and TEMPO-terminated block copolymer grafted carbon black

The purpose of this study was to modify the surface characteristics of CB so as to prevent the aggregation of CB to provide the dispersibilities in either H₂O or organic solvent. In this study, five kinds of hydrophilic TEMPO-terminated polymer, hydrophobic TEMPO-terminated polymer and amphiphilic TEMPO-terminated block copolymer were synthesized. The five kinds of TEMPO-terminated polymers were: (1) poly(4-acetoxystyrene) (PAS-T), (2) poly(4-hydroxystyrene) (PHS-T), (3) polystyrene (PS-T), (4) poly(4-acetoxystyrene)-block-polystyrene (PAS-b-PS-T), (5) poly(4-hydroxystyrene)-block-polystyrene (PHS-b-PS-T). These TEMPO-terminated polymers with desired molecular weights and specific structures were synthesized by using the method of living radical polymerization in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO). These TEMPO-terminated polymers and TEMPO-terminated block copolymers were grafted onto the surface of CB through a reaction of polymer radicals trapped by CB, so as to obtain the TEMPO-terminated polymer/CB and TEMPO-terminated block copolymer/CB composite nanoparticles. Various variables such as reaction time, reaction temperature, amount of TEMPO-terminated polymer, molecular weight of TEMPO-terminated polymer and amount of CB all of which influenced the grafting efficiency were investigated. Besides, the stability of the composite nanoparticles, which dispersed in H₂O or organic solvent, was investigated by laser light scattering. The amphiphilic composite nanoparticles, PHS-T/CB and PHS-b-PS-T/CB, which dispersed well in both H₂O and organic solvent, were synthesized successfully in this work.     

Differential reactivity of SH bonds towards platinum(0). Direct synthesis of a low symmetry platinum (II) complex with hydrido, phosphine and N,S-cysteinato ethyl ester ligands

The chelate assisted oxidative addition of the H---S bond of L-cysteine esters HSCH₂C^*H(COOR)NH₂ (R = Me, Et), to Pt(PPh₃)₄ yields the low symmetry cysteine complexes [Pt(H)(SCH₂C^*H(COOR)NH₂)(PPh₃)] in one step, with displacement of three moles of triphenylphosphine, only when an excess of the cysteine ester is used. With HSCH₂CH₂NH₂ the excess is not necessary: the 1:1 reaction yields [Pt(H)(SCH₂CH₂NH₂)(PPh₃)]. Bulkier HSCH₂CH₂NMe₂ and HSCMe₂CH(COOMe)NH₂ (penicillamine methyl ester) do not react, even when an excess of ligand is used. 2-Aminothiophenol gives trans-[Pt(H)(SC₆H₄-2-NH₂)(PPh₃)₂] and does not form a chelate complex.     

A new inorganic (carbon-free) chelate ring: SnO2N2. Eight-coordinated tin(IV) in Sn(O2N2Ph)4 and a self-assembled 20-membered macrocycle in [Me3Sn(O2N2Ph)]4

The reaction of cupferron (NH₄L, L=PhN(O)NO⁻) with tin(IV) and trimethyltin(IV) halides yields cupferronato complexes SnL₄ (1) and [Me₃SnL]₄ (2) which were characterised by FT-IR and FT-Raman spectroscopy. The first X-ray diffraction analysis of the complexes reveals a slightly distorted dodecahedral and trigonal-bipyramidal coordination of the central metal atoms in 1 and 2, respectively. The N-nitroso-N-phenylhydroxylaminato [PhN(O)NO⁻] ligand behaves as chelating in 1 and bridging in 2 leading to a novel five-membered chelate ring, SnO₂N₂ in 1 and an unprecedented 20-membered inorganic metallomacrocycle, Sn₄O₈N₈ in 2.     

N-Picolyl-N′-benzoylthiourea, H2picbtu – A new ligand with a remarkable coordination mode. Synthesis and structures of H2picbtu and its tetrameric oxorhenium(V) complex

(NBu₄)[ReOCl₄] reacts with N-picolyl-N′-benzoylthiourea (H₂picbtu) in acetone under formation of the deep-green oxorhenium(V) complex (NBu₄)₂[{Re₂O₂Cl₅(Hpicbtu)}₂O], which was studied by X-ray diffraction. Two dimeric units with each one bridging, singly deprotonated thiourea ligand are connected by an oxo ligand. Inside the subunits, Hpicbtu⁻ coordinates as S,O chelate with a six-membered chelate ring to one rhenium atom, while a five-membered chelate ring is established with the second Re atom and the nitrogen atoms of the picolylamine building block. The compound represents one of the very rare examples of anionic μ-oxorhenium(V) complexes.     

Synthesis and characterization of the dihydrosalpren ligand (H2L1) and of its trinuclear Ni(II) complex

The synthesis of the new unsymmetrical tetradendate Schiff ligand N-(2-hydroxybenzyl)-N′-(2-hydroxybenzylidene)-1,3-diaminopropane (H₂L¹) is reported. The ligand comprises two different coordination moieties: a rigid salicylaldimmine unit and a more flexible (2-hydroxybenzyl)-amino (hydrogenated salicylaldimmine) unit. The reaction of H₂L¹ with Ni(OAc)₂·4H₂O (1:1 molar ratio) leads to the spontaneous formation of a trinuclear complex with composition {[Ni(L¹)OH₂]₂(OAc)₂Ni}·2H₂O, characterized by X-ray crystallography, where two [Ni(L¹)] units act as O,O-bidentate chelate to a Ni(II) ion.     

Synthesis and characterization of new bivalent tin chelate of 3-hydroxy-2-methyl-4-pyrone and its use as catalyst for polyesterification

Summary We describe here the synthesis of a new tin chelate Sn(C₆H₅O₃)₂.2H₂O. The catalytic performance of this chelate is shown for polyesterification reactions involving terephthalic acid and poliols, such as neopentylglygol and trimetilolpropane. The complex is highly active for low molecular weight (M_n= 1700 and M_w= 4500) polymer formation. IR spectra also show free OH in the polymer chain. Received: 26 June 2000/Revised version: 4 October 2000/Accepted: 6 October 2000     

Enzymatic acyl modification of phosphatidylcholine using immobilized lipase and phospholipase A2

Ethanol‐soluble (ES) lecithin mainly contains phosphatidylcholine (PC). The incorporation of caprylic acid into PC using immobilized phospholipase A₂ (PLA₂) and lipase was investigated. The Rhizomucor meihei lipase and the porcine pancreatic PLA₂ were immobilized on the hydrophobic resin Diaion HP‐20 and the modification was carried out in hexane as solvent. HPTLC with densitometer technique was successfully used for monitoring the production of structured phospholipids (PL) (ML‐type PC, MM‐type PC, and lysophosphatidylcholine; L: long‐chain fatty acid, M: medium‐chain fatty acid). The various parameters such as the effects of reaction temperature, enzyme loading, and the effect of molar proportion of substrate were studied in order to determine the optimum reaction conditions for the acidolysis reaction. The optimal operating conditions for the PLA₂‐catalyzed reaction were obtained as 50°C temperature, 50% (wt/wt of substrate) enzyme loading, and a 1:12 molar proportion of PC/caprylic acid. For the lipase‐catalyzed reaction, the optimized temperature was the same as for PLA₂, but the enzyme loading and molar proportion were slightly lower, i.e., 40 % w/w of substrate and 1:9 PC/caprylic acid, respectively. The effects of these parameters on the production of structured PL were compared. Under these optimal conditions, the ML‐type PC content was higher in the PLA₂‐catalyzed reaction, i.e., 45.29 mol%, and in the lipase‐catalyzed reaction it was 38.74 mol%.     

Synthesis and self-assembly of amphiphilic polyphosphazene with controllable composition via two step thiol-ene click reaction

Sequential thiol-ene click reaction is reported for amphiphilic glycosylated polyphosphazene. Poly[bis(allylamino)phosphazene] was used as precursor to go through UV irradiation with 2,3,4,6-tetra-O-acetyl-1-thiol-β-D-glucopyranose (SH-GlcAc₄) and 1-dodecanethiol in sequence. Variation of the reaction conditions, including click reaction time and the dose of photoinitiator, led to different hydrophilic/hydrophobic ratios. As a result, glycosylated polyphosphazenes were synthesized with 53.3%, 77.7% and 85.0% of glucose moieties. The different residual composition could give rise to different self-assembly behaviors. Micelles of amphiphilic polyphosphazenes were formed in aqueous solution and the CMC value (0.79 × 10⁻³–4.00 × 10⁻³ mg/mL) as well as mean diameter (170–220 nm) varied along with the hydrophilic glucose moiety/hydrophobic dodecyl moiety ratio.     

Preparation and properties of fluorinated silicon two‐component polyurethane hydrophobic coatings

A polyurethane (PU) hydrophobic coating was prepared by the two‐component method, polycarbonate diol and isophorone diisocyanate becoming a two‐phase composition. The PU films with hydrophobic surface were prepared by establishing a rough structure on the surface of silica (SiO₂) modified with silane coupling agents (γ‐(2,3‐epoxypropoxy)propytrimethoxysilane (KH560) and (heptadecafluoro‐1,1,2,2‐tetradecyl)trimethoxysilane (FAS)). First, the surface of SiO₂ was covered by a layer of hydrophobic methyl and fluorocarbon (C–F) groups. Then, the SiO₂ and modified SiO₂ were obtained by the introduction of KH560 and FAS with the silanol reaction by ultrasonic stirring. The effect of SiO₂ and modified SiO₂ on the structure and hydrophobic properties of PU was investigated by a series of test instruments. The results showed that the introduction of SiO₂ and modified SiO₂ was beneficial for increasing the roughness of the PU coating surface; the roughness of FAS/SiO₂‐PU could reach up to 14.790 nm, four times better than pure PU. A hydrophobic modified PU coating with water contact angle 123° was fabricated by using the hydrophobic C–F group FAS as a low surface energy material and establishing a micro rough structure on the surface of PU. Moreover, PU modified with KH560 and FAS can reduce the glass transition temperature (T_g) of soft segments, resulting in improvement of micro‐phase separation. © 2020 Society of Chemical Industry     

Oxidative absorption of hydrogen sulfide using an iron‐chelate based process: chelate degradation

BACKGROUND: Oxidative absorption of hydrogen sulfide into a solution of ferric chelates is studied in a stirred cell glass reactor. The experiments were performed to investigate the degradation of chelates sodium salt of nitrilotriacetic acid (NTA) (Merck), ethylenediaminetetraacetic acid diadisodium salt (EDTA) and diethylenetriaminepentaacetic acid (DTPA) at 313 K, pH 6, iron concentration 10 000 g L^?1 and Fe:chelate molar ratio 1:2. RESULTS: Oxidative absorption of hydrogen sulfide into a solution of Fe‐NTA was found to be more successful, therefore, further experiments with 10%, 50% and 100% concentrations of hydrogen sulfide were performed. It was shown that this process is applicable for removal of low and high concentrations of hydrogen sulfide. The effect of antioxidants using sodium thiosulfate was also studied in order to minimize degradation of NTA. The kinetics were studied and it was observed that the reaction appeared to be first order in ferric chelate with rate constants for 100, 50 and 10% hydrogen sulfide concentration: 0.035, 0.013 and 0.019 h^?1, respectively. CONCLUSIONS: Gas sweetening processes have commercial importance in natural gases, refinery of gases and biogas processing. Desulphurization and cleaning (i.e. removal of H₂S and CO₂) of petroleum gas and biogas is important to make the gas methane rich and to increase the calorific value of fuel. The same techniques of desulphurization and cleaning can be used for treating natural gas or petroleum gas. The desulphurization and cleaning processes can minimize the atmospheric emission of gases like SOx, NOx and CO. As the iron chelate based process is based on the principle of redox reaction of metal chelate with hydrogen sulfide, this method is very useful for desulphurization of petroleum gas and biogas. This work studied the effective use of Fe‐NTA solution for removal of high to low concentrations of H₂S as found in biogas and industrial waste gases. © 2012 Society of Chemical Industry