A Strategy for Preparing Star Polymers Containing Metal–Metal Bonds Along the Polymeric Arms Using Click Chemistry

The [(η⁵-C₅H₄(CH₂)₃N₃)Mo(CO)₃]₂ dimer (3) was prepared and used to determine if the Huisgen cycloaddition reaction could be used to synthesize high molecular weight star polymers with metal–metal bonds in the arms. Several different click catalysts were examined. Cp*Ru(PPh₃)₂Cl (Cp* = η⁵-C₅(CH₃)₅) was previously shown to catalyze the formation of metal–metal bond-containing polymers using click chemistry; however, this catalyst underwent a Staudinger reaction with dimer 3 when a model coupling reaction was attempted with phenylacetylene. In order to avoid the Staudinger reaction, Cp*Ru(COD)Cl was used as the catalyst in the reaction of 3 with phenylacetylene, and coupling was observed after 14 h. Synthesis of a star polymer was attempted with 3 and 1,3,5-triethynylbenzene. Instead of coupling, Cp*Ru(COD)Cl reacted with the 1,3,5-triethynylbenzene. A third catalyst, Cu(IMes)Cl (IMes = 1,3-dimesityl-imidazol-2-ylidene) was used to couple 3 with 1,3,5-triethynylbenzene in 48 h. Both a high molecular weight polymer (M _n  = 77,000 g mol^?1) and a tripodal star core (M _n  = 1,800 g mol^?1) were successfully prepared with this catalyst.     

Synthesis of ROMP Monomers Containing Metal–Metal Bonds

Methods for the synthesis of cyclic monomers that have both metal–metal bonds and carbon–carbon double bonds are reported. Ring opening metathesis polymerization (ROMP) of these monomers would yield polymers that are photochemically degradable. The first method investigated involved substitution of Cp₂Fe₂(CO)₄ by the bidentate phosphine ligand DPPEN (Ph₂P CH=CH–PPh₂). Cp₂Fe₂(CO)₂( -DPPEN) was synthesized and the X-ray crystal structure is reported but the molecule could not be polymerized by a ROMP method using Grubbs’s catalyst. The inability of this monomer to polymerize (or copolymerize with cyclooctatetraene) was attributed to the bulky phenyl rings being in close proximity to the C=C in the DPPEN ligand, which prevents coordination of the monomer to the catalyst. To decrease the steric interactions, the DPPBN ligand was synthesized (DPPBN=Ph CH CH=CH CH PPh₂). However, the reaction of DPPBN with Cp₂Fe₂(CO)₄ yielded the product Cp₂Fe₂(CO)₂( -1,2,4-triphos), where the 1,2,4-triphos ligand is a tridentate ligand formed by the formal additional of Ph₂PH to DPPBN (1,2,4-triphos=Ph CH CH(PPh₂) CH CH PPh₂). An X-ray structure of the Cp₂Fe₂(CO)₂( -1,2,4-triphos) complex revealed that the 1,2,4-triphos ligand chelates exclusively through the two phosphorus atoms that are bridged by two carbon atoms. It is suggested that this structural feature may simply reflect the increased stability of the 6-membered ring over the 7- and 8-membered rings. The reactions of the Cp₂Mo₂(CO)₆ and Cp₂Mo₂(CO)₄ dimers with DPPBN were investigated next. Reactions of Cp₂Mo₂(CO)₆ and Cp₂Mo₂(CO)₄ with the DPPEN and DPPBN ligands resulted in the disproportionation of the dimers. The X-ray crystal structure of [CpMo(CO)₂(DPPEN)][CpMo(CO)₃] was determined and is reported. The CpMo(CO)(DPPEN)Cl complex was formed when these same reactions were carried out in the presence of CH₂Cl₂. The X-ray crystal structure of this molecule is also reported.     

Synthesis and Properties of Polymers with an Organosilicon–Acetylene Backbone

Acetylene- and diacetylene-containing organosilicon polymers continue to be of great interest in academia, government, and industry due to their high thermo-oxidative stability combined with excellent solubility and processability characteristics. Progress in this field over the past 30 years is reported herein. We present and discuss the synthesis, characterization, and structure–property relationships related to these materials. Furthermore, properties for specific applications of these polymers are briefly summarized, such as absorption and emission spectroscopy, composite mechanical analysis, four-probe conductivity measurements, and electroluminescence.     

Structural Basis for Intumescence – Part III – Thermal Degradation Study of Intumescent Polymers Containing Spirophosphorus Moiety in the Backbone

3,9-Dichloro-2,4,8,10-tetraoxo-3,9-disphosphaspiro-[5.5]-undecane-3,9-dioxide (spiro) was melt condensed with structurally different dihydric phenols to form poly aromatic spirophosphates. The thermal volatilization analysis showed eruptive release of gases above 300°C and the temperature region of release depends on the nature of the aromatic units incorporated in the polymer backbone. The thermal degradation in nitrogen atmosphere indicated the formation of phenol, substituted phenols, aromatics, alkyl and alkenyl substituted aromatics and condensed aromatics like azulenes, indanes and fluorenes. The source for the formation of these products is the spiropentadiene released from the spiro unit during degradation.     

Atomic Scale Observations of the Chemistry at the Metal–Oxide Interface in Heterogeneous Catalysts

Here we present a preliminary analysis of the atomic scale interface chemistry in a model heterogeneous catalyst system, Pt/SiO₂. We show that the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) exhibits a sensitivity to surface oxidation and changes in the interfacial chemistry that is higher than that of conventional analytical methods such as energy-dispersive X-ray spectroscopy (EDS), chemisorption, and X-ray absorption near edge structure analysis (XANES). In particular, the presence of a few monolayers of platinum oxide can be clearly seen, and changes in the chemistry of the SiO₂ support within ∼1 nm of the metal–oxide interface can be characterized as a function of the catalyst preparation conditions. These results demonstrate that this combination of novel techniques can provide unparalleled information that is potentially the key to understanding the activity and selectivity of heterogeneous catalyst systems.     

Metal Complexes of π-Conjugated Polymers

π-Conjugated chelating polymers such as poly(2,2′-bipyridine-5,5′-diyl), poly(1,10-phenanthroline-3,8-diyl), and salophen polymers have been prepared by organometallic polycondensations. The obtained polymers form metal complexes with various metal species such as [Ru(bpy)₂]²⁺ and CuCl₂. Metal complexes of π-conjugated ligands are also polymerized by dehalogenative organometallic polycondensations. Some of the metal complexes of π-conjugated polymers exhibit electrical conducting nature and show catalytic activity for redox reactions.     

Structural Basis for Intumescence—Part II: Synthesis and Characterization of Intumescent Polymers Containing Spirophosphorus Moiety in the Backbone

Taking the spirophosphorus compound 3,9-dichloro-2,4,8,10-tetraoxo-3,9-diphosphaspiro-[5,5]-undecane-3,9-dioxide as one of the reactive monomers, a family of aromatic spirophosphates was synthesized using dihydric phenols, viz., resorcinol, hydroquinone, 4,4′–dihydroxydiphenyl, bisphenol-A and fluorene dicarbinol as the other monomers. The polymers were synthesized employing melt condensation technique under vacuum and characterized using FT-IR, ¹H-, ¹³C- and ³¹P-NMR spectroscopic methods. The number average molecular weight of the polymers was determined using vapour phase osmometry. Thermal properties of the polymers were studied using differential scanning calorimetry and thermogravimetry techniques. These studies indicated that the polymers containing spirophosphato moiety undergo eruptive degradations in the temperature region 310°–380°C leading to the formation of dense carbonaceous foam. The present study confirmed the spirophosphate structure as an essential requirement to show intumescence.     

Reactive Phosphazene–Siloxane Polymers for Materials Chemistry

Catenapoly(dimethyl-⁵-phosphazene-co-methylphenyl-⁵-phosphazene) functionalized by electrophilic substitution of a methyl hydrogen atom with reactive Si(OMe)₃ groups grafts easily to glass or cross-links to free-standing films by hydrolysis and further condensation of the silicon functional group. The manufactured films exhibit a high gas permeability.     

Self-Assembly of Nanostructures on Surfaces Using Metal–Organic Coordination

Layer-by-layer (LbL) assembly of multilayers is an established method for the construction of layered nanostructures on surfaces, affording control of the thickness, composition, and organization in the vertical direction. Binding between layers is accomplished using various types of interactions, including electrostatic binding, hydrogen bonding, covalent bonding, metal–organic coordination, host–guest interactions, biospecific interactions, and others. Here we focus on LbL assembly using metal–organic coordination, and specifically on layered nanostructures based on bishydroxamate–M⁴⁺ binding. The coordination approach offers attractive features, such as a simple reaction, a defined geometry, and reversibility under certain conditions. The basic scheme includes self-assembly of a ligand (anchor) monolayer on the surface, followed by alternate binding of metal ions and multi-functional ligand layers, to form a coordination multilayer. This approach is demonstrated by the construction of a variety of coordinated nanostructures, including bilayers, multilayers, dendrimers, and nanoparticle assemblies, prepared on gold and oxide substrates.     

Preparation and Properties of Novel Quaternized Metal–Polymer Matrix Nanocomposites

A new class of PANI/Sn(II)SiO₃/FCNTs nanocomposite was synthesized by mixing polyaniline into the gel of Sn(II)SiO₃ followed by FCNTs (Polyaniline/Sn(II)SiO₃/Functionalized Carbon nanotubes). The physico-chemical characterization was carried out by scanning electron microscope, XRD (X-ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), ultraviolet–visible spectroscopy, and simultaneous thermogravimetric analysis studies. The ion-exchange capacity (1.2 meq/g) and distribution studies were also determined to understand the ion-exchange capabilities. The DC electrical conductivity studies revile it in the range of 3–5 × 10^?3 S/cm. On the basis of distribution studies, ion-selective membrane electrode was designed for Hg(II). The analytical utility of this membrane was established by using it as an indicator electrode in electrometric titrations.     

The Polymerization of Metal-Containing Vinylic Monomers of Iron and Tungsten with Metal–Carbon σ Bonds

A series of metal-containing vinylic monomers of the type and was homopolymerized using 2,2-azobisisobutyronitrile (AIBN) as the free-radical initiator. These monomers were also copolymerized with styrene in the presence of AIBN. These compounds represent a class of organometallic polymers in which the metal is bonded to the polymer backbone via a metal–carbon bond. The new compounds were characterized by IR and ¹H NMR spectroscopy as well as scanning electron microscopy, gel permeation chromatography, and thermoanalytical studies (DSC and TGA). The properties of the new organometallic polymers are discussed.     

Affinity Dialysis–A Method of Continuous,Rapid Metal Ion Separation Using Dialysis Membranes and Selective,Water-Soluble Polymers as Extractants

Abstract

A membrane process utilizing dialysis and selective complexation by water-soluble polymers has been developed. This process, termed affinity dialysis, has been shown to selectively extract and concentrate both cations and anions in a manner similar to ion exchange or solvent extraction. The selective removal of calcium from sodium with selectivity of about 30, removal of chromate ion from dilute streams, and separation of transition metal ions such as Cu/Fe and Cu/Zn have all been successfully demonstrated. Effects of different polymers, polymer concentration, temperature, and flow rates have been studied. The effect of increased polymer concentration is to increase product concentration if appropriate changes in feed, polymer solution, and strip flow rates are made. A continuous polymer solution recycle and regeneration system has been constructed and operated with Cu/Zn and chromate/chloride feed streams. Removal of over 95% of the desired ion in one pass and concentration factors of product over effluent in excess of 100 have been achieved at feed flow rates of 24 gal/d. Product concentrations of greater than 3% from as little as 400 ppm feed have been demonstrated in a continuous process. In addition, the degree of polymer loss to the effluent stream has been shown to be less than 0.01%/d for a typical system. Metal removal from typical feeds is about 0.9 g/m² per 1000 ppm metal in the feed. It is expected that this technique may be useful in the separation of organic and biological materials, as well as for ionic species     

Response Surface Modeling of Processing Parameters for the Preparation of Phytosterol Nanodispersions Using an Emulsification–Evaporation Technique

The purpose of this study was to optimize the production parameters for water-soluble phytosterol nanodispersions. Response surface methodology (RSM) was employed to model and optimize three of the processing parameters: mixing time (t) by conventional homogenizer (1–20 min), mixing speed (v) by conventional homogenizer (1,000–9,000 rpm) and homogenization pressure (P) by high-pressure homogenizer (0.1–80 MPa). All responses [i.e., mean particle size (PS), polydispersity index (PDI) and phytosterols concentration (Phyto, mg/l)] fitted well to a reduced quadratic model by multiple regressions after manual elimination. For PS, PDI and Phyto, the coefficients of determination (R ²) were 0.9902, 0.9065 and 0.8878, respectively. The optimized processing parameters were 15.25 min mixing time, 7,000 rpm mixing speed and homogenization pressure 42.4 MPa. In the produced nanodispersions, the corresponding responses for the optimized preparation conditions were a PS of 52 nm, PDI of 0.3390 and a Phyto of 336 mg/l.     

Antibacterial Properties of Ester—Cross-Linked Cellulose–Containing Fabrics Post-Treated with Metal Salts

To improve the performance properties of cellulose-containing fabric, ester was cross-linked with polycarboxylic acid in the presence of specific catalysts. Its pendant carboxyl groups were exploited in binding some heavy metals (by reacting with some salts, such as zinc acetate, zinc chloride, zinc sulfate, cupric acetate, cupric chloride, cupric sulfate, and nickel sulfate) capable of imparting their antibacterial activity toward some gram-positive bacteria (viz., B. subtilis, B. mycoides, Sta. aureus) and a gram-negative bacteria (E. coli). Zinc salts impart to the fabric the highest antibacterial activity, followed by cupric acetate. Zinc chloride proved to be the metal salt that yielded the maximum antibacterial activity.     

Evaluation of the Effect of Nanosilica on Thermal and Mechanical Properties of Metal–Metal and Metal–Glass Canola-Based Polyurethane/Nanosilica Adhesives

Nanocomposites with different concentration of nanofiller were prepared by adding nanosilica to the canola-based polyurethane matrix via in situ polymerization. The effect of nanosilica on the mechanical properties of adhesives was evaluated by tensile tests. Adhesive characteristics on metal–metal and metal–glass bondings were also evaluated by lap shear strength tests. Incorporation of nanosilica into the canola-based polyurethane enhanced both tensile and lap shear strength of synthesized adhesives. Also the effect of nanoparticles on glass transition temperature and thermal stability was investigated by differential scanning calorimetry and thermogravimetric analysis, respectively. The increase of nanosilica content in the polyurethane adhesives, thermal property of the nanocomposites improved.     

Synthesis of PNIPAM–PEG Double Hydrophilic Polymers Using Oleic Acid Macro Peroxide Initiator

This work refers to the synthesis of a new double hydrophilic thermo‐responsive polymer using fatty acid macroperoxide initiator, N‐isopropyl acryl amide (NIPAM) and polyethylene glycol with two primary amine ends (PEGNH2). For this purpose, oleic acid was spread out onto a petri dish and exposed to air oxygen at room temperature for 2 months. The obtained fatty acid macro‐peroxide initiator was used in the free radical polymerization of NIPAM in the presence of PEGNH2. Poly oleic acid‐g‐PNIPAM‐g‐PEG graft copolymers were successfully obtained. Lower critical solution temperature (LCST) of the graft copolymer was determined by using UV‐Vis spectrometry with a sensible heating unit. Morphology of the fractured surface of the double hydrophilic polymers was visualized by using SEM micrographs. Graft copolymers with LCST close to body temperature were obtained by changing PEG inclusion. Structural characterization, thermal analysis and size exclusion chromatography measurements of the obtained products were done.     

Hydroprocessing of Aromatics Using Sulfide Catalysts Supported on Ordered Mesoporous Phenol–Formaldehyde Polymers

Ni–W sulfide catalysts for the hydroprocessing of aromatic hydrocarbons were synthesized by the in situ decomposition of tetrabutylammonium nickel thiotungstate complex supported on ordered mesoporous phenol–formaldehyde polymer. Catalysts obtained with and without additional sulfidation with dimethyl disulfide were characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The catalytic activity has been studied using naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, and anthracene as examples. It is shown that the system used in this study proved to be active in hydrogenation and hydrocracking of polyaromatic hydrocarbons.     

An Oxidation System for Green Chemistry: The Oxidation of Alcohols and Hydrocarbons in the Presence of Metal–Polymer Complexes

Environmental and economic factors make the use of harmful oxidants increasingly unacceptable except on a small scale. Accordingly, we have investigated the use of dioxygen and hydrogen peroxide as oxidants. For this oxidation reaction of hydrocarbons, transition metal complexes and polymer-bound transition metal complexes were effective as catalysts. Earlier investigations indicated that the catalytic site was a bi- or multinuclear complex. Thus, several binuclear complexes of Cu and Mn [Eqs. (9)–(11)] were designed and their effectiveness in oxidizing phenols to biphenols and benzoquinones and in monooxygenase activity was demonstrated. In the oxidation of phenols, the system did not produce poly(phenylene oxide) since the intermediate phenoxy radical underwent C–C coupling to biphenol or underwent attack by hydroxyl radical to a hydroquinone that could be oxidized to a quinone. A reaction mechanism involving the binuclear complex for the oxidation is proposed.     

Synthesis and Sulfonation of an Aluminum-Based Metal–Organic Framework with Microwave Method and Using for the Esterification of Oleic Acid

Journal of Inorganic and Organometallic Polymers and Materials - In this study, the synthesis of MIL-53(Al) (Material Institute Lavoisier, MIL) material, which is an aluminum-containing...