Methylene Bridged P(III) and P (V) Phosphiniminato-Phosphanes: Versatile Ligands And Substituents for Metals and Metalloids

Abstract

Recent studies¹ have shown that the mono oxidized phosphanolminatophosphane Me₃SiN=PPh₂CH₂PPh₂ 1 is a versatile ligand for a variety of transition metals in high and low oxidation states. This heterodifunctional ligand may bind to metals via the “hard” (N) or the “soft”(P(III)) centres; the former favours high oxidation states and “early” transition metals, the latter, low oxidation states and “late” transition metals. Monodentate or bidentate complexation is observed and in the latter case chelation or bridging is possible. Elimination of Me₃SiCl from a metal halide or migration of Me₃Si group to a terminal oxygen atom leads to metal nitrogen sigma bond formation. To modify the basicity at nitrogen a variety of approaches have been employed. Metathetical elimination of Me₃SiX from activated halogenated aromatics leads to functionalisation at N. The R₃Sn and R₃Ge analogs of 1 have also been made by extensions of the Staudinger reaction. Reactions of 1 and its N-aromatic, N-Ge, and N-Sn analogs with a variety of metals wiil be described. In water, 1 produces the unstable parent imine which has been trapped as a coordination complex of Pd(II) and Pt(II) metals. The reactions of halides produces a variety of N substituted compounds of non metals (eg; =N-SePh) and metals (eg; =N-TiR₃) which demonstrate the important heterodifunctional character of the ligand system.     

High Performance Liquid Chromatography of Low Molecular Weight Proteins on a Non-Ionic Macroreticular Polystyrene Resin

Abstract

A high performance liquid chromatography system is presented for analytical and preparative separation of proteins. The method utilizes a macroreticular polystyrene resin having no specific functional groups, and proteins are eluted by the use of linear gradient of acetonitrile (20% ?75%, v/v) in 0.1% (v/v) trifluoroacetic acid. In this standard elution system, twenty proteins having a molecular weight of 4,200–58,000 and an iso-electric point of 3.9–11.0 have been chromatographed successfully within 80 min. The method allows a rapid, sensitive, and high resolution separation of relatively low molecular weight proteins, where the isolated proteins can be used for subsequent biochemical determinations.     

Effect of Liquid Animal Manure Application on the Solubilization of Heavy Metals from Soil

Abstract

The effect of liquid animal manure on heavy metal solubilization in soil has been studied in the laboratory; three different types of experiments were carried out:

1) aerobic and anaerobic incubation of soil/manure mixtures

2) desorption of heavy metals from soil, as affected by manure liquid fraction

3) gel permeation chromatography of soil/manure aqueous extracts to identify components responsible for heavy metal solubilization.

Alf three different approaches showed that complexation involving high molecular weight dissolved organic matter from the soil/manure matrix is (together with pH) the most important driving force for heavy metal solubilization. As a consequence, chemical and microbial processes (e.g. nitrification) that influence dissolved organic matter concentrations in the soil solution, determine the degree of heavy metal solubilization in manured soil.     

Synthesis of Poly(Ether Sulfone)s End-Capped with Metal Containing Phthalocyanines

Abstract

A series of low molecular weight poly(aryl ether sulfone)s with metallophthalocyanine (PcM) end groups were synthesized by reacting o-phthalonitrile end-capped poly(aryl ether sulfone)s with excess phthalonitrile and metal salts/metals in high boiling solvents. The metals selected for this study were copper and iron. The polymers were soluble in common organic solvents. They were characterized by ¹H NMR, IR, GPC and UV-VIS spectroscopy. Appearance of an absorption band at around 700 nm confirmed the presence of phthalocyanine moieties in these polymers. The possibility of occurrence of any stacking phenomenon of the PcM rings was studied by annealing the polymers in a Thermo-Gravimetric/Differential Thermal Analysis (TG/DTA) instrument. An increase in T_g was observed for the PcM containing polymers perhaps indicating the aggregation of the terminal PC rings in the solid state.     

Olefin Polymerizations and Copolymerizations with Aluminum Alkyl-Cocatalyst Systems. V. The Molecular Weight and Molecular Weight Distribution of Polystyrene

Abstract

The polymerization of styrene with the cationic initiator system AlR₂Cl/RCl was investigated further. Earlier conclusions [1] were corroborated and expanded by an analysis of the number and weight average molecular weights. Alkyl halides with low (high) R?Cl bond dissociation energies are efficient (poor) coinitiators of the polymerization of styrene. In the presence of efficient RCl coinitiators, the molecular weights strongly decrease and the molecular weight distributions strongly increase with increasing conversions (Fig. 1). With poor cointiators, only low conversions are obtained even in the presence of large amounts of AlEt₂Cl. The data are discussed in terms of a previously proposed mechanism [1].     

Characterization of Nonionic Polyacrylamides by Aqueous Size Exclusion Chromatography Using a DRI/LALLSP Detector System

Abstract

Herein is reported an experimental investigation of the molecular weight characterization of nonionic polyacrylamides by aqueous SEC with a DRI/LALLSP detector system. Methodology for the use of the DRI/LALLSP detector responses to determine the molecular weight calibration curve and the peak broadening parameter, [sgrave]² (variance of a Gaussian instrumental spreading function) over a wide molecular weight range has been developed. The method is based on the use of a broad MWD standard made by blending Polysciences broad MWD standards and a generalized analytical solution of Tung's integral equation for the detector response corrected for peak broadening. Molecular weight averages measured by SEC/DRI/LALLSP are in excellent agreement with those measured offline by LALLSP.     

Copolymerization and Copolymers of 2,4,5-Tribromostyrene with Methyl Acrylate and Methyl Methacrylate

Abstract

2,4,5-Tribromostyrene (TBSt) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in a toluene solution using 2,2′-azobisisobutyronitrile as free radical initiator. The copolymerization reactivity ratios were found to be for the system TBSt / MA r₁= 7.4 ± 1.2 (TBSt) and r₂= 0.1 ± 1.4 (MA) and for the system TBSt / MMA r₁ = 1.8 ± 0.2 (TBSt) and r₂ = 0.1 ± 0.2 (MMA). The e and Q values were also calculated. The initial rate of copolymerization, as well as molecular weight of the obtained copolymers for both system linearly increase as the content of TBSt in the monomer mixture increases. Similar behavior has also been established for the course of the copolymerization reactions to high conversions. The resulting copolymers rapidly decompose at temperatures 20–800°C above the decomposition of corresponding (metha)crylate hompolymers. However, the glass transition temperature increases markedly with increasing TBS content.     

Direct construction of silicon-silicon bond by using the low-valent titanium reagent

The reductive dimerization or polymerization of organochlorosilanes has been achieved by using the low-valent titanium reducing agent other than the alkali metals that are invariable used in the Wurtz-type coupling reaction. Applying this method, the corresponding disilanes or poly(methylvinylsilane) was obtained in good yields. The poly(methylvinylsilane) synthesized by this method is highly pure with a high molecular weight and a narrow molecular weight distribution (M_w/M_n = 1.6, M_n = 16,860).     

Gel Permeation Chromatography of Polyethylene Terephalate

Abstract

This paper describes the development of the gel permeation chromatography (GPC) technique for the measurements of cyclic trimer content, molecular weights, and molecular weight distribution of polyethylene terephthalate (PET), utilizing a solvent system of o-chlorophenol-chloroform. Mark-Houwink constants for this solvent system are also described.

The GPC technique was applied to the study of the cyclic trimer content, molecular weights and molecular weight distribution of a variety of commercial PET resins. The results indicate that the cyclic trimer content in PET is dependent on molecular weight, polycondensation process and catalyst system. Solidstate polymerized PET contains less cyclic trimer than PET made by the melt-phase process of the same molecular weight. The cyclic trimer content in solid-stated PET appears to be dependent on the conditions of solid-state polymerization.

The polydispersity index determine for a variety of PET samples is higher than the theoretically predicted value of 2.0; however, there is no systematic dependence on molecular weight or polycondensation process.     

Living Carbocationic Polymerization of Isobutylene Using Blocked Dicumyl Chloride or Tricumyl Chloride/TiCI4Pyridine Initiating System

Abstract

Living polymerization of isobutylene was achieved using an initiation system based on either 1,3-di(1-chloro-l-methylethyl)-5-tert-butylbenzene (tert-butyl-dicumyl chloride) or 1,3,5-tris(l-chloro-l-methylethyl)benzene (tricumyl chloride) in conjunction with TiCl₄, and pyridine in hexanes/methyl chloride (60/40, v/v) cosolvents. TiCl₄/pyridine was found to yield narrow molecular weight distribution (MWD ≈ 1.1) and quantitative initiation efficiency (I_eff < 90%). The living nature of the polymerization system was demonstrated by the linearity of molecular weight vs conversion plots and first-order kinetic plots up to about 90% monomer conversion. If polymerization was allowed to proceed further, a departure from first-order kinetics and a broadening of the molecular weight distribution was observed to occur. The living polymerization was investigated as a function of temperature, reaction time, and the concentration of TiCl₄/pyridine. Polymerization rates were observed to increase with decreasing temperature and/or increasing concentration of TiCl₄/pyridine. Number-average molecular weights of the polyisobutylenes ranged from 5,000 to 100,000 under the conditions employed.     

Rare Earth Metal-Initiated Polymerizations of Polar and Nonpolar Monomers

Abstract

Organolanthanide(III) initiated polymerization of methyl methacryate gave both syndiotactic and isotactic living polymers of high molecular weight. Organolanthanide(III) initiated polymerization of alkyl acrylates also gave high molecular weight poly(alkyl acrylate)s with very narrow molecular weight distribuion in high yield. Molecular weights of the resulting polymers increased linearly with the conversion. Random and block copolymerizations of alkyl acrylates with methyl methacrylate were realized successfully. For the sake of development of the olefin polymerization catalyst, bulky substituents were introduced into Me₂Si bridged Cp rings and they were used as ligands for the lanthanide complexes. Tri- and divalent lanthanide complexes with such ligands showed high activity for olefin polymerization and gave high molecular weight polyolefins.     

Distribution of Heavy Metals in Water and Soil Solutions Based on Colloid-Size Fractionation

The distribution of heavy metals Cr, Ni, Zn, Cu, Cd, and Pb among the truly dissolved (molecular weight cutoff <1 kD), colloidal (1 kD-0.20 µm and 0.20-0.45 µm) and particulate (>0.45 µm) fractions was investigated in the soil solution and surface water. In 15 soil solutions heavy metals were mainly present in the truly dissolved fraction (<1 kD) with occasional exceptions. And a good correlation was also found between the concentrations of metals in the truly dissolved fractions and the cation exchange capacity of soils. As for the surface water samples, the distribution pattern was more complicated one depending on metal properties and sampling sites.     

A Thermal Decomposition and Glass Transition Temperature Study of Poly(p-chlorostyrene)

Abstract

The thermal decomposition and the glass transition temperature of poly(p-chlorostyrene) (PpCIS) were studied with a Model 2 differential scanning calorimeter (DSC). The undecom-posed and decomposed polymers were analyzed by gel permeation chromatography for molecular weight distributions and by DSC for changes in the polymer glass transition temperature. The decomposition of PpCIS under isothermal conditions during 50 min intervals at various temperatures or at a fixed temperature (320°C) but for different periods is characterized by the disappearance of increasing quantities of high molecular weight polymer and the appearance of low molecular weight products. Random scissions have been shown to break down the polymer chains which depolymerize into volatile products. Activation energy (72 kcal/mole) for the decomposition of PpCIS is lower than that (103 kcal/mole) for the decomposition of polystyrene.     

Molecular Weight Characterization and Structural Properties of Controlled Molecular Weight Dextrans Synthesized by Acceptor Reaction using Highly Purified Dextransucrase

ABSTRACT

Controlled molecular weight dextrans were synthesized using a highly purified dextransucrase from Leuconostoc mesenteroides NRRL B-512F in a multi-step process. Maltose was used as acceptor for the first reaction step. The purified product obtained at a given reaction step was used as acceptor for the next reaction step. Dextrans of molecular weights ranging from 1,000 to 100,000 were thus obtained with a good yield (80 %). After purification, the molecular weight distribution of the products was characterized using size exclusion chromatography coupled with low angle laser light scattering (LALLS). Polydispersity of the products was shown to be similar to that of commerical dextrans.

¹³C NMR spectra and enzymatic hydrolysis data are consistent with the fact that the enzymatically synthesized dextrans are essentially composed of α(1->6) linkages. It was observed that controlled molecular weight dextrans were less branched than commercial products obtained by acidic hydrolysis of high molecular weight dextrans.     

Low-Temperature Polyesterification of 3-Hydroxy-2-Phenylpropionic Acid

Abstract

The synthesis of poly(3-hydroxy-2-phenylpropionic acid), prepared from tropic acid and 1,3-dialkylcarbodiimide (cyclohexyl or isopropyl) with p-toluenesulfonic acid (PTSA) and/or dimethylaminopyridine (DMAP) as catalysts, has been investigated. Molecular weight and yield have been found to vary inversely with temperature and solvent polarity. Dialkylcarbodiimide activation of the carboxylic acid is enhanced when PTSA and DMAP are used in equal concentrations. Highest molecular weights and yields were achieved at ? 20°C with 50% (mol% of monomer) DMAP and PTSA in a cyclohexane/THF solvent system.     

Combination of asymmetric flow field-flow fractionation (AF4) and total-reflexion X-ray fluorescence analysis (TXRF) for determination of heavy metals associated with colloidal humic substances

To assess the structural variability of colloidal humic substances and the associated heavy metals an off-line coupling of asymmetric flow field-flow fractionation (AF⁴) with total-reflection X-ray fluorescence analysis (TXRF) is presented. AF⁴ allows a rather gentle separation of colloids with a minimum of interference and artifacts as no shear forces, drying, or interactions with a stationary phase are involved. After a calibration with suitable polymer particles of known molecular weight, the molecular weight distribution of colloidal humic substances between 1 and 10³ kDa can be assessed with AF⁴. The combination with TXRF permits a simultaneous multielement analysis after preconcentration of samples on the AF⁴ channel using an optimized buffer. The analysis of seepage and sewage water sample and a sewage sludge sample yielded continuous distributions of the molecular weight and the associated heavy metals. The potential of AF⁴-TXRF coupling for the study of metal ion exchange equilibria with colloids was demonstrated by spiking seepage water with various heavy metals and subsequent AF⁴-TXRF analysis of the heavy metals bound to the colloidal fraction (Cu, Cr, Zn, Ni, Co).     

Linear and Hyperbranched Poly(arylene ether)s from a New Semifluorinated AB Monomer

A new trifluoromethyl-activated AB monomer has been successfully synthesized by Pd-initiated coupling of 4-bromo anisole with 4-fluoro-3-trifluoromethylphenylboronic acid followed by demethylation. The monomer leads to a semifluorinated poly(arylene ether) by nucleophilic displacement polymerization reaction. The AB monomer has been further copolymerized with a corresponding AB ₂ monomer to form the corresponding semifluorinated hyperbranched (hb) poly(arylene ether). The resulting linear and hb poly(arylene ether)s exhibited weight average molecular weight of 75700 and 144100 g/mol, respectively. The hb copolymer exhibited better solubility in different organic solvents compared to the linear poly(arylene ether). The polymers showed excellent thermal stability up to 522°C at 10% wt loss in air and glass transition temperatures as high as 187°C. The mechanical properties of the linear poly(arylene ether) film 1a exhibited tensile strength at break of 89 MPa, elongation at break of up to 3% and a Young’s modulus value of 2.66 GPa. The films of the polymers were hydrophobic in nature and showed water contact angle as high as 93.6°.     

Determination of Microcystins in Cyanobacteria by Supercritical Fluid Extraction and Liquid Chromatography‐Tandem Mass Spectrometry

Abstract

A method for the detection of microcystins (microcystin LR, RR, and YR) in cyanobacteria by supercritical fluid extraction (SFE) and liquid chromatography‐mass spectrometry (LC/MS) has been developed. Supercritical fluids for the analytical extraction of nonvolatile, higher molecular weight compound, and microcystins from cyanobacteria were investigated. The microcystins included in this study are sparsely soluble in neat supercritical fluid CO₂. However, the microcystins was successfully extracted with a ternary mixture (90% CO₂, 9.5% methanol, 0.5% water) at 40°C and 250 atm. The polar carbon dioxide‐aqueous methanol fluid system gave high extraction efficiency for the extraction of the polar microcystins from cyanobacteria. The microcystins were determined by liquid chromatography‐tandem mass spectrometry (LC/MS/MS).     

Reaction Of Nitrides And Oxide With Bath Metals In Gas Analysis In Metals

Abstract

Reactions of two nitrides, an oxide (α-SiaNi, A1N and α-AI2O3) and bath metals (platinum, iron and tin) in graphite capsules were investigated in vacuum fusion analysis by measuring gas extraction curves with a quadrupole mass spectrometer which can simultaneously measure nitrogen and carbon monoxide from the furnace. From the characteristic gas extraction patterns of each bath metals, gas release reaction mechanisms and their temperatures were studied.     

Polymerization of N,N-Dialkylacrylamides with Anionic Initiators Modified by Diethylzinc

Abstract

N,N-Dimethyl-, diethyl-, and dipropylacrylamides were polymerized with 1,1-bis(4′-trimethylsilylphenyl)-3-methylpentyllithium (I) in the presence and absence of diethylzinc in THF. Although the polymers produced with I in the absence of diethylzinc have rather broad molecular weight distributions, the addition of diethylzinc to the polymerization systems causes narrow molecular weight distributions of the polymers. The addition of diethylzinc also affect the stereospecificities of the polymers obtained. The poly(N,N-diethylacrylamide) produced with I/diethylzinc (molar ratio of 1/3-15) is highly syndiotactic, while the one obtained with I is isotactic. The configuration of the poly(N,N-dimethylacrylamide) is changed from isotactic to syndio and heterotactic rich by the addition of diethylzinc to the polymerization mixture. Little effect of diethylzinc is observed on the stereospecificity of the polymerization of N,N-dipropylacrylamide. The stoichiometric additive effect of Et₂Zn toward the initiator in the polymerization of DEAA suggests that the coordination of Et₂Zn aggregates with the propagating carbanionic species narrows the molecular weight distribution and controls the tacticity of the polymer.