Study of polymer-bound mixed valence palladium catalysts. I. Preparation and characterization of polymer-bound mixed valence palladium catalysts

Polymer-bound palladium catalysts of different valence have been prepared by reducing PdCl₂ with a proper reductant, i.e., hydrazine hydrate, under certain conditions. ESR, XPS and IR were used to characterize the catalysts. Pd ⁺ was prepared for the first time and found to be stable on the polymersupport. The authors also investigated the influences of the reducing conditions, the surface properties of polymer supports and the effectsof reducing agents on the degree of reduction of divalent palladium bound onto the polymers, and the state of the palladium after reduction. The experimental results showed that the coexistence of different valence states of palladium in the supports may be Pd ²⁺, Pd^O; Pd²⁺, Pd⁺ (or Pd^δ+); Pd^O and Pd²⁺ Pd⁺ (or Pd^δ+), Pd^O. The method of preparing catalysts of mixed valence is described.     

Synthesis and characterization of bisitaconimides. I

This article describes the synthesis and characterization of bisitaconimides on the basis of 4,4′‐diaminodiphenylether, 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane, 1,3‐bis(4‐aminophenoxy)benzene, and 1,4‐bis (4‐aminophenoxy)benzene. Isomerization of the itaconimides to citraconimides (varying in the range of 25–40%) was observed during synthesis. The curing exotherm and thermal stability of the cured resins depended on the backbone structure of itaconimides. The curing exotherm immediately followed the melting endotherms. These resins cured at lower temperatures than bismaleimides but thermal stability of cured bismaleimides was higher than bisitaconimides. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2277–2282, 2002     

Polyacrylic desalination membranes. I. Synthesis and characterization

A new class of desalination membranes has been developed. The membranes were prepared by polymerizing mixtures of two hydrophilic monomers (N-methyloacrylamide and acrylic acid), a hydrophobic monomer (ethyl acrylate) and a hydrophobic crosslinking monomer (trimethylol propane trimethacrylate) followed by heat treatment. The membranes were homogeneous, averaging about 6 mils in thickness. They were characterized by measuring water contents and salt distribution coefficients using an immersion technique. The fractional water contents in the membranes varied between 0.16 and 0.44 as the molal salt distribution coefficients increased from ca. 0.22 to 0.43. Increasing contents of the hydrophobic monomer and/or crosslinking monomer led to decreased water and salt contents, as expected. A model is postulated in which the water is assumed to be distributed within the polymer in two forms: (1) as primary water, hydrogen-bonded with hydrophilic polymer groups, and (2) secondary water, imbibed with salt from the external solution into hydrophilic regions or defects within the polymer matrix. It was found that primary water content was approximately constant for all compositions and varied between ca. 2–3 moles of primary water/mole of hydrophilic monomer in the membrane.     

Tetrafunctional aliphatic epoxy I. Synthesis and characterization

A low viscosity tetrafunctional epoxy resin was synthesized by reacting amino-terminated polydimethylsiloxane with epichlorohydrin followed by dehydrohalogenation. The synthesized tetrafunctional aliphatic epoxy resin had an epoxy equivalent weight of 382, M_n of 1492, M_w of 2296, and a viscosity of 4.2 poise at 25°C. The chemical structure of the tetrafunctional aliphatic epoxy resin was studied by gel permeation chromatography (GPC), Fourier transform infrared spectra (FTIR), and ¹H-NMR spectra. Results showed the tetrafunctional aliphatic epoxy-blended aromatic epoxy resin possessed high impact strength and flexural strength. SEM photographs were investigated to study the compatibility of the blended epoxy system. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 51–58, 1998     

Synthesis and characterization of carbon-supported nanoparticles for catalytic applications

Metallic and carburized tungsten nanoparticles have been prepared using WCl₆ as precursor. The synthesis steps lead from tungsten hexachloride to tungsten carbide following the sequence WCl₆ → W⁰ → α-W₂C → WC. These different compounds have been mainly characterized by X-ray diffraction, TEM observations and adsorption measurements. The total reduction of tungsten hexachloride can be completed at T = 973 K. The carburizing of the metallic lattice into carbide WC is observed at 1223 K although incomplete. At this temperature, crystal growth phenomena appear which are not desired for catalysis applications. The synthesis of nanoparticles supported on activated carbon is accompanied by a decrease of the specific surface area of samples, especially during high temperature carburizing.     

Synthesis and characterization of water-soluble polyaspartamide-ferrocene conjugates for biomedical applications

Polymer-ferrocene conjugates are synthesized from the polyamide1, poly-,-dl-[N-(3-(morpholin-4-yl)propyl)aspartamide-co-N-(2-aminoethyl)aspartamide, through coupling of amino side groups with the carboxyl function in a number of ferrocenylcarboxylic acids, including ferrocenoic acid, ferrocenylacetic acid, 3-ferrocenylpropanoic acid, 3-ferrocenylbutanoic acid, 4-ferrocenylbutanoic acid, and 4-ferrocenyl-4-hydroxypentanoic acid. The ferrocene complex has been chosen for conjugation by virtue of the cytotoxic properties observed with some of its derivatives. The coupling reactions, mediated by HBTU (O-benzotriazolyl-N,N,NN-tetramethyluronium hexafluorophosphate), are brought about inN,N-dimethylformamide solution and lead to degrees of substitution in the range of 25–95%. The resulting conjugates2, fractionated by dialysis in tubing with a 12,000–14,000 molecular mass cutoff and collected in the solid state by freeze-drying, are completely soluble in water after isolation and retain this property in frozen aqueous solutions. Preliminary electrochemical data are reported, indicating a decreasing (i.e., less positive) potential with increasing length of the aliphatic, electron-donating connecting link between the ferrocene and the carboxamide anchoring group. The 4-ferrocenylbutanoyl substituent is associated with the least positive potential of those structures investigated and, hence, should provide conjugates with optimalin vivo stability in the ferricenium state. Selected conjugates will be submitted to screening tests for antineoplastic activity.Metallocene polymers 46. For Part 45, see Ref. 1.     

Synthesis and characterization of calcium aluminate nanoceramics for new applications

Two types of nanocalcium aluminate powders containing 70 and 60 wt.% Al₂O₃ were prepared by thermal decomposition and investigated in terms of mineralogical composition, hydration, mechanical properties and microstructure. The results revealed that S1 is composed mainly of the CA and CA₂ phases, while S2 composed of CA and C₁₂A₇ phases after heat-treatment at 1000 °C. The maximum crystallite sizes for S2 and S1 were 44 and 52 nm and the minimum ones 12 and 19, respectively. Both samples still have small crystallite size after heat-treatment at 1000 °C. The present phases, i.e. CA, CA₂ and C₁₂A₇ affect the properties of hydrated and sintered ceramic bodies. S2 hydrated sample achieved higher strength (58.5 MPa) than S1 (52.4 MPa). The higher strength of S2 is ascribed to the presence of CA and C₁₂A₇ as a major component, since it reacts rapidly with water. In S1, the poor hydration of CA₂ at the early stage of hydration lowers strength after 7 days hydration as compared with S2. Cold crushing strength (CCS) data of the sintered ceramics bodies exhibit high strength of both samples after firing at 1550 and 1450 °C for S1 and S2, respectively. This is due to the formation of a ceramic bond.     

Synthesis and characterization of phenolic resole resins for composite applications

In this study, phenol–formaldehyde resins catalyzed with sodium hydroxide, triethylamine, and ammonium hydroxide were investigated and characterized in terms of their degradation behavior, flammability, mechanical properties, and chemical structure. All three resins displayed similar degradative mechanisms, and their degradation behavior was broken down into three distinct stages. These stages were attributed to the evolution of water, the volatilization of species loosely bound to the phenolic backbone, and bulk degradation of the phenolic matrix. Flammability studies were also performed on glass fiber laminates manufactured from these resins. The sodium-hydroxide- and ammonium-hydroxide-catalyzed resins were found relatively inflammable, while the triethylamine-catalyzed laminates burned readily. The mechanical properties of the resins were found to be similar or higher than the mechanical properties of other untoughened epoxies or thermosetting resins. The various chemical properties responsible for these behaviors are discussed and analyzed in terms of the catalyst basicity, solubility, and boiling point. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 505–514, 1999     

Synthesis and characterization of polyarylureas. I. Potentially semiconducting polymers

Polyarylureas were synthesized from the reaction between phosgene with aromatic diamines. Depending on the pH, the polyarylureas presented different colors when the solvent used was pyridine. The polyarylureas were characterized by IR spectroscopy, elemental analysis, and X‐ray photoelectron spectroscopy (XPS). To study the thermal stability of the polymers, a thermal degradation was performed between 35 and 700°C. The polyarylureas decomposed above 350°C. Without doping, polyarylureas are considered as semiconductors [σ = 10^?9 (Ωcm)^{? 1}]; after doping with I₂, their electrical conductivity increases by several orders of magnitude. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 822–830, 2001     

New conducting thermoplastic elastomers. I. Synthesis and chemical characterization

In the last 20 years, much interest has been focused on conducting polymers to find new materials to transfer from research to industry. However, in many cases, as for elastomers for which intrinsically conducting materials are unavailable, it is necessary to use conducting particles that are physically mixed with the polymeric matrix to give loaded rubbers. In this work we report the synthesis and the chemical characterization of an intrinsically conducting material with good mechanical and electrical conduction properties. To achieve such a global goal, we covalently linked, by an amidation reaction, the terminal NH₂ of Emeraldine (EB) and sulfonated Emeraldine (SPAN) to a free carboxylic group belonging to the repetitive unit of a functionalized segmented polyurethane. The reaction was carried out by activating such a carboxylic group with N,N′‐dicyclohexylcarbodiimide and N‐hydroxysuccinimide. The reaction yields and the chemical properties of the polymers were studied by proton and carbon‐13 nuclear magnetic resonance, ultraviolet, and Fourier transform infrared spectroscopy. The average numbers of EB or SPAN aromatic rings per polyether urethane acid (PEUA) repetitive unit, which cannot be assumed to be amidation degree because at this moment the molecular weights of the inserted EB and SPAN chains are unavailable, were 6 in case of the polymer obtained from the pristine Emeraldine and 1 for that obtained from the sulfonated Emeraldine. This result could be because SPAN was used in the acidic form, which depresses the nucleophilicity of the NH₂ group because of the presence of the sulfonic protons. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 857–867, 2002     

Synthesis and characterization of methacrylate phospho-silicate hybrid for thin film applications

Phosphorus containing methacrylate hybrids were synthesized from 2-(methacryloyloxy)ethyl phosphate (EGMP) and 3-[(methacryloyloxy)propyl] trimethoxysilane (MEMO) via dual-cure process involving sol-gel reaction and addition polymerization. The kinetics of the reactions was established using spectroscopic techniques. Photoacoustic Fourier transform infrared spectroscopy (PA-FTIR) and X-ray photoelectron spectroscopy (XPS) confirm the formation of Si-O-Si, P-O-P and Si-O-P linkages and simultaneous polymerization of methacrylate groups leading to a dense networked structure. The presence of silicate/phospho-silicate network in the hybrid enhances its thermal stability. Nanoindentation measurements on thin films show enhanced hardness and modulus with increasing silicate network. Topographic and conductivity images obtained using micro-thermal analysis (μTA) reveal a dense, homogenous and defect-free thin film formed on metallic substrate with a T_g of 93 °C.     

Aromatic polyamide–imides as materials for membranes. I. Synthesis and characterization

Diamine amic acids were synthesized by reacting aromatic diamines with pyromellitic dianhydride in dimethylacetamide/dioxane. High molecular weight polyamide-amic acids were prepared by low-temperature solution polymerization of diamine amic acids with isophthaloyl chloride in dimethylacetamide. The cyclodehydration of polyamide-amic acids to the corresponding polyamide–imides was accomplished by heating the cast films at 175°C for 3 h. The polyamide–imides were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone and could be cast into tough and flexible films. They were characterized by elemental analyses, inherent viscosities, IR, and ¹H-NMR spectra. The glass transition temperatures of polyamide–imides were determined by differential scanning calorimetry. The thermal stabilities of the polymers were measured by thermogravimetric analyses in air. © 1995 John Wiley & Sons, Inc.     

Novel polyaryletherketones containing various pendant groups. I. Synthesis and characterization

Novel high glass transition temperature polyaryletherketones, containing pendant amido, alkyl, and carboxyl groups with reduced viscosity above 0.54 dL/g, were synthesized via solution nucleophilic polycondensation reaction of phenolphthalin, 2′,2′-diisopropyl-5′,5′-dimethylphenolphthalin, and 3,3′-bis (4-hydroxyphenyl) isobenzopyrrolidone with bis(4-nitrophenyl)ketone in the presence of potassium carbonate. By ion exchange with Na⁺ and K⁺, four ionomers were also prepared. A new monomer simultaneously containing carboxyl and alkyl substituents was synthesized by reduction reaction of 2′,2′-diisopropyl-5′,5′-dimethyl-phenolphthalein. The resulting polymers were soluble in a few polar aprotic solvents; transparent, colorless, and tough films could easily be cast from DMF or DMSO solution. The mechanical properties of the films were excellent; and their tensile strength, elongation at break, and tensile moduli were in the range of 67.1–97.1 MPa, 7.8–165%, and 1.47–2.27 GPa, respectively. The prepared polymers showed fairly good thermal stability and resonably high glass transition temperatures above 210°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1127–1135, 1997     

Bisphenol-A polycarbonate/polydimethylsiloxane multiblock copolymers. I. Synthesis and characterization

Aminopropyl-terminated polydimethylsiloxane (PDMS)-bisphenol-A polycarbonate block copolymers were synthesized by interfacial phosgenation reaction of 2,2-bis(4-hydroxyphenyl) propane (BPA) and aminopropyl-terminated PDMS. A new synthetic procedure shows better conversion yield of PDMS oligomer. IR, ¹H, ¹³C, and ²⁹Si nuclear magnetic resonance spectra were used to identify the exact chemical structures of the PDMS-PC block copolymers. The conversions of PDMS of these copolymers were ∼ 90% and independent of the PDMS content. The intrinsic viscosities, IV, [γ] studied were in the range between 0.23 and 2.25 dL/g in dichloromethane at 25°C with different reaction conditions. The intrinsic viscosity and the glass transition temperature decreased with increasing PDMS content at the same reaction temperature, while the melting flow indices increase with increasing PDMS content. Transparent and colorless films, which showed good oxygen-to-nitrogen permselectivity, could be cast from dichloromethane. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 57–66, 1997     

Guar gum methyl ethers. Part I. Synthesis and macromolecular characterization

Guar gum (GG) has been partially methyl-etherified under heterogeneous reaction conditions. The resulting products, (methyl ether guar: MG) with different degrees of substitution, have been characterized by means of viscosity, ¹H NMR, and FTIR measurements. The introduction of methoxyl groups along the polysaccharidic chains reduces the hydrogen bonding sites on the guar backbone reducing primarely the extent of hydrogen bonding between guar macromolecules, hence their aggregation tendency. A comparative analysis of Mark–Houwink–Sakurada parameters and of the characteristic ratio (C_∞) of GG and MG samples in aqueous solution has been carried out using the Burchard–Stockmayer–Fixman method for flexible and semiflexible chains. The MG chains exhibit more flexibility than those of native guar gum which is traceable to a disruption of intrachain hydrogen bonds.     

Synthesis and characterization of modified cottonseed oil based polyesteramide for coating applications

Cottonseed oil fatty amide (CFA) was prepared in the laboratory by base catalyzed aminolysis of cottonseed oil. Further it was reacted with phthalic acid to obtain polyesteramide (CPEA) and modified by post reacting with vinyl acetate monomer in varying ratios of 4:1, 3:1 and 2:1 in the presence of t-butyl hydroperoxide as an initiator. The incorporation of vinyl acetate in CPEA was analyzed using FTIR, ¹H NMR and ¹³C NMR spectral techniques. The physico-chemical properties such as iodine value, specific gravity and refractive index were determined by standard laboratory test methods. Mechanical, chemical resistance and other coating properties of the coatings synthesized from CPEA and modified CPEA applied on mild steel substrates were also studied by standard methods. Thermal stability and curing behavior of modified CPEA were determined by thermo gravimetric analysis (TGA) and differential scanning calorimetric (DSC) techniques. It was observed that modification of polyesteramide improved the curing, mechanical and chemical performance of CPEA films. It was found that among the CPEA:vinyl acetate ratios, 2:1 ratio exhibited the best results.     

Synthesis and characterization of novel polyurethanes containing tricyanocyclopropane ring for piezoelectric applications

Summary 1-(2',2',3'-Tricyano-3'-carbomethoxycyclopropyl)-3,4-di-2'-hydroxyethoxybenzene (4) was prepared by the reaction of bromomalononitrile with methyl 3,4-di-(2'-hydroxyethoxy)benzylidenecyanoacetate (3). Diol 4 was condensed with 3,4-toluenediisocyanate and 3,3'-dimethoxy-4,4'-biphenylenediisocynate to yield polyurethanes 5 and 6 containing multicyanocyclopropane functionalities in the pendant group. The resulting polymers 5 and 6 were soluble in common organic solvents and the inherent viscosities were in the range of 0.25–0.30 dL/g. Polyurethanes 5 and 6 showed a thermal stability up to 300°C in TGA thermograms. Solution-cast films showed T _g values in the range of 100–130°C and piezoelectric coeffcients (d₃₁) of the poled polymer films were 1.8–2.0 pC/N, which are acceptable for piezoelectric device applications. Received: 14 December 2000/Accepted: 22 January 2001     

Studies on water-swellable elastomer. I. Synthesis and characterization of amphiphilic polymer

A new amphiphilic polymer i.e., polyethylene glycol (PEG) grafted crystalline neoprene, which was used as compatibilizer to improve the compatibility of elastomer and water-absorbent resin, has been investigated. The synthesis was based on the reaction between chlorine in neoprene and sodium salts of PEG. PEGs with molecular weights of 600 and 2000 were used. The grafting percent and the PEG content were calculated through elemental analysis of chlorine in the resulted copolymers. The maximum grafting percent of copolymers was ca. 24.80%. The molecular parameters such as number-average molecular weight and the average number of grafting chains on one CR backbone were also calculated and discussed. © 1996 John Wiley & Sons, Inc.