Oligomeric Poly Ethylene Research Articles

Analysis of Polyethylene by Using Cyclopentadienyl Cobalt Chemical Ionization Combined with Laser-Induced Acoustic Desorption/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

A new mass spectrometric method has been developed for the analysis of low molecular weight polyethylene (PE). Laser-induced acoustic desorption (LIAD), combined with chemical ionization by the cyclopentadienyl cobalt radical cation (CpCo.+) in a Fourier transform ion cyclotron resonance mass spectrometer, produces predominantly a quasimolecular ion, (R + CpCo - 2H2).+, for each PE oligomer (R). An examination of artificial alkane mixtures revealed no mass bias for alkanes of differing molecular weights. However, the success of the LIAD/CpCo.+ CI technique depends greatly upon the LIAD sample preparation method used. Several sample preparation methods were evaluated, and pneumatically assisted spin coating was concluded to provide the best mass spectra as a result of its ability to provide uniform PE coverage on the LIAD foils. The molecular weight distributions measured for several low molecular weight PE samples (200-655) were found to be in good agreement with manufacturers' values as determined by gel permeation chromatography.

Relaxation Properties of Pressure-sensitive Adhesives upon Withdrawal of Bonding Pressure

ABSTRACT Relaxation properties of pressure-sensitive adhesives (PSA) have been studied with the squeeze-recoil tester used in the regime of parallel-plate dilatometer under conditions imitating the removal of compressive force in the course of adhesive bond formation. The relaxation properties of PSAs are compared with their adhesive behavior measured using the 180-Deg Peel Test. Two classes of PSAs are considered: 1) conventional rubbery adhesives based on the mixtures of styrene-isoprene-styrene (SIS) block copolymer with a tackifier resin and a plasticizer, and butyl rubber plasticized with low-molecular-weight polyisobutylene, and 2) hydrophilic PSAs composed of the blends of high-molecular-weight poly(N-vinyl pyrrolidone) (PVP) with oligomeric polyethylene glycol (PEG). By comparing the adhesive and relaxation behaviors of different PSAs, the relaxation criteria for pressure-sensitive adhesion have been stated. Relaxation behavior of the examined PSAs demonstrates two values of retardation time: the shorter retardation time of 10–70 sec and the longer time of 300–660 sec. These times can be associated, respectively, with small- and large-scale mechanisms of strain recovery. By comparing the relaxation and adhesive properties of PVP-PEG blend (which involves the formation of a hydrogen-bonded network through both terminal hydroxyl groups in PEG short chains) with the properties of covalently crosslinked copolymers of vinyl pyrrolidone (VP) with PEG-diacrylate and comb-like VP copolymers with PEG-monomethacrylate, the contributions of covalent crosslinking and H-bonding network have been characterized.

Late-Transition-Metal Complexes with Bisazaferrocene Ligands for Ethylene Oligomerization

Herein we report the synthesis, characterization, and ethylene polymerization properties of novel C2-symmetric and unsymmetric bisazaferrocene complexes with late-transition-metal Ni(II) and Pd(II). In the designed complexes, the two sp2-hybridized nitrogen atoms in the azaferrocene rings coordinate to the transition metals with the azaferrocene architecture presenting pentamethyl or pentaphenyl cyclopentadiene (Cp* or Cp°) rings above and below the coordination plane for the purpose of preventing the associative chain transfer processes of ethylene from the axial faces. The Ni(II) and Pd(II) complexes were prepared and characterized by mass spectrometry (MS), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Upon activation with methylaluminoxane (MAO), the bisazaferrocene complexes with NiBr2 (2a) and PdCl2 (2b) showed very low activities toward ethylene polymerization. Well-defined preactivated bisazaferrocene-Pd(II) complexes (5 and 6) exhibited relatively high thermal stability for ethylene oligomerization: for example, complex 5 remains active in ethylene oligomerization at temperatures up to 120 °C. They have moderate activities in ethylene polymerizations to form relatively low molecular weight oligomers. The polyethylene oligomers formed have branching densities ranging from 20 to 60 branches/1000 carbons. To overcome the difficulty encountered in the synthesis of complex 6, a novel route was developed to make Pd(Me)Cl complexes with various dinitrogen ligands by in situ ligand substitution reaction. Finally, to gain mechanistic insight into the low reactivity of the bisazaferrocene-PdII complexes (5 and 6) as compared to their α-diimine counterparts, kinetic studies were undertaken to measure the energetic barriers for the first methyl migration and subsequent ethylene consumption. It was found that the insertion barriers (ΔG⧧) for both the first methyl migration and subsequent ethylene insertion for complex 5 were about 2−3 kcal/mol higher than the values for the α-diimine counterparts, which corresponds to a 2-order difference in the rate of polymerization. Variable-temperature experiments further revealed that the higher ethylene insertion barrier for the bisazaferrocene-Pd(II) complexes arises from both higher activation enthalpy (ΔH⧧) and smaller activation entropy (ΔS⧧).

STUDYING ABNORMAL VISCOSITY BEHAVIOR IN DILUTE OLIGOMER SOLUTIONS BY SEC AND RHEOLOGY

ABSTRACT We report here on the study of oligomer solutions with negativeviscosities, i.e., the viscosity of the solution is less than that of the neatsolvent (η<η s ) or the intrinsic viscosity of thesolution is less than zero ([η]<0), observed both in Poiseuille andCouette flow. These effects have been measured for several concentrations ofnon-functionalized styrene monomer in DMAc/ 0.5% LiCl at 35°Cand for functionalized styrene monomer as well as for different concentrationsof polyethylene oligomer in trichlorobenzene at elevated temperature. In bothcases, measurements were performed as part of a size-exclusion chromatography(SEC) set-up, utilizing differential viscometers of the Wheatsone bridge type.The SEC configuration, using high-resolution oligomeric columns, permittedunambiguous determination of the degree of polymerization at which the solutionviscosity changes from positive to negative in DMAc/LiCl, with static lightscattering detection ruling out the possibility of an analyte clustering effectbeing responsible for the observed behavior. Ultimately, an appropriateexplanation for this unusual effect was provided by steady-shear rheometrymeasurements of styrene-DMAc/LiCl mixtures, applying predictive rules forone-phase binary mixtures.

Modification of Polypropylene and Polyethylene Oligomers (Waxes)

Modification of Polypropylene and Polyethylene Oligomers (Waxes)

Asymmetric Curvature of {110} Crystal Growth Faces in Polyethylene Oligomers

Lamellar crystals laterally bounded by {110} faces only (nontruncated lozenges) are obtained from 1% octacosane solutions of alkanes n-dohexacontahectane (C162H326) and n-octanonacontahectane (C198H398) at the highest crystallization temperatures, i.e., 103 °C < Tc < 108 °C and 108 °C < Tc < 110 °C, respectively. This is in contrast with polydisperse polyethylene where {110}-bounded lozenges form only at low Tc. Crystals grown from 1-phenyldecane at the highest Tc are also nontruncated. However, while the crystals obtained from octacosane are faceted and rhombic, those grown from phenyldecane have their {110} faces asymmetrically curved at the obtuse apexes. This gives the crystals a leaf-shaped appearance, normally associated with {100}-bounded lamellae. To distinguish it from the established {100} bounded lenticular crystal morphology, the new habit is designated “a-axis lenticular”. The particular type of curvature found for {110} faces is explained qualitatively by assuming a different rate of propagation in the two opposite directions of a new layer of stems. The “sharp” step travels faster, at a rate vs, toward the acute apex, while the “blunt” step travels more slowly, at a rate vb, toward the obtuse apex. The asymmetry is due to the absence of a mirror plane bisecting the {110} growth face.

RHEOLOGICAL STUDY OF SOME MELTS OF HIGH-DENSITY POLYETHYLENE INTENSIVELY CHARGED WITH SURFACE-TREATED CaCO3. II. THE ELASTIC COMPONENT

The present paper resumes the studies devoted to the obtention of charged polyolefins and discusses the influence of the CaCO3 surface treated with a compatibilization agent (polyethylene oligomer) on the elastic component of composites possessing a high-density polyethylene matrix. Based on a genuine algorithm, which starts from the output pressure off the rheological nozzle, the rheological parameters characterizing the elastic component of the highly-charged polyethylene melts' flow are calculated and analyzed. It has been demonstrated that the introduction of the treated charging material transforms the intensively charged composites into thermoplastic alloys.

Non-integer and mixed integer forms in long n-alkanes observed by real-time LAM spectroscopy and SAXS

Application of real-time Raman longitudinal acoustic mode (LAM) spectroscopy is demonstrated in the studies of comparatively fast crystallising and transforming monodisperse polyethylene oligomers. The experiments have confirmed the structural model of the transient non-integer folded (NIF) form in long-chain n-alkane C246H494 derived previously from real-time small-angle X-ray scattering (SAXS). During crystallisation of the NIF and its subsequent isothermal transformation into the once-folded form F2 a single fundamental (LAM-1) peak of constant frequency is observed, which corresponds to the straight chain segment length exactly equal to half the full chain length. This confirms that crystalline core layers of the NIF have a constant thickness corresponding to that of the once-folded form F2. The remaining thickness making up the full lamellar periodicity thus consists of an amorphous layer made up of cilia. The constant frequency, but increasing intensity of the LAM-1 band during isothermal annealing is consistent with the cilia crystallising by re-entering the existing crystalline layers. In alkanes C210H422 and C198H398 another mechanism of transformation of the NIF into a more stable structure is observed. A new mixed-integer folded–extended (FE) phase forms instead of the pure once-folded F2 phase. Instead of re-entering the existing crystal layer, the cilia from two neighbouring NIF lamellae gather and form a third intercalated crystalline layer. The resulting superstructure contains three crystalline layers in a repeat unit. Whether one or the other of the two transformation modes take place appears to depend on factors such as fraction of folded chains in the NIF, overcrowding at the crystal-amorphous interface and chain diffusion.

Inorganic‐Organic Composite Solid Polymer Electrolytes

Inorganic‐organic composite solid polymer electrolytes (CSPEs) have been prepared from the poly(ethylene oxide) (PEO)‐like electrolytes of the general formula polyvinylidene fluoride‐hexafluoropropylene and ceramic powders. In the PEO‐like electrolytes, PVdF‐HFP is the copolymer of PVdF and HFP, is a nonvolatile oligomeric polyethylene oxide of ∼400 g/mol molecular weight, and LiX is lithium bis(trifluoroethylsulfonyl) imide. Two types of inorganic oxide ceramic powders were used: a highly material of the composition 14 mol % , and the poorly Li‐silicates where M is Ca or Mg and x is 0 or 0.05. The composite electrolytes can be prepared as thin membranes in which the conductivity and good mechanical strength of the inorganic ceramics are complemented by the structural flexibility and high conductivity of organic polymer electrolytes. Excellent electrochemical and thermal stabilities have been demonstrated for the electrolyte films. Li//composite electrolyte// rechargeable cells have been fabricated and cycled at room temperature and 50°C. © 2000 The Electrochemical Society. All rights reserved.

Influence of Electric Field Strength and Emitter Temperature on Dehydrogenation and C—C Cleavage in Field Desorption Mass Spectrometry of Polyethylene Oligomers

The influence of electric field strength and emitter temperature on dehydrogenation and C–C cleavage in field desorption (FD) mass spectrometry of polyethylene (PE) oligomers of average molecular weights ranging from 500 to 2000 is examined. Low mass oligomers yield molecular weight (MW) distributions that are basically in accordance with results from gel-permeation chromatography. For these materials, dehydrogenation can be greatly reduced by reduction of the emitter potential. Furthermore, the influence of emitter potential on MW distributions indicates the occurrence of field-induced C–C cleavages. Reliable MW distributions are more difficult to obtain from higher mass oligomers by FD-MS because of the need for higher field strength and higher emitter temperatures to effect their desorption/ionization. Experiments reveal that the application of FD-MS to PE oligomers is limited not only by field-induced but also by thermally-induced fragmentations. Even then, FD mass spectra contain valuable information on mass range and homogeneity of PE samples up to about m/z 3600.

Synthesis of polyynes (and ene-ynes) segments by dechlorination reactions of chlorinated polyethylene wax and chlorinated docosane

High density polyethylene oligomers and docosane (C22H46) were subjected to a photochlorination reaction to a chlorine content above 70% as checked by thermogravimetry. The resulting chlorinated materials were dehydrohalogenated by potassium hydroxide in different conditions with simple reaction routes. It is shown by FT-IR, C13-NMR and electronic spectroscopy that soluble low molecular weight polymers were formed having polyyne-ene and polyene-yne segments. These new soluble polymeric materials are of potential interest both in the field of optics and electronics as well as in the understanding the cosmochemical problem of the molecules in interstellar space.

Electronic structure and molecular orientation of well-ordered polyethylene oligomer (n-C44H90) on Cu(100) and Au(111) surfaces studied by UV photoemission and low energy electron diffraction

Abstract The electronic structure and molecular orientation of tetratetracontane (n-C44H90) films on Cu(100) and Au(111) surfaces were investigated by angle-resolved UV photoemission spectroscopy (ARUPS) and low energy electron diffraction (LEED). The observed ARUPS spectra showed the drastic take-off angle dependence due to intramolecular band dispersion. A 2×1-like LEED pattern was observed for both substrates. From these results and theoretical simulation of ARUPS spectra based on independent-atomic center (IAC) approximation, we found that the C–C–C plane of the adsorbed TTC molecule is parallel to the substrate surface and its molecular axis is along a [110] direction for both substrates. We also measured the work function change by adsorption of TTC. The observed values were c.a. −0.3eV and −0.7eV for Cu(100) and Au(111) systems, respectively. Such decrease of the work function indicates the existence of a dipole layer at the interfaces in contrast to the traditional picture of energy level alignment at organic/metal interface assuming a common vacuum level at the interface. The dipole formation in such physisorbed systems can be explained by the polarization of the TTC molecule due to an image force.

Rational Design of a Hexagonal Columnar Mesophase in Telechelic Alternating Multicomponent Semifluorinated Polyethylene Oligomers

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTRational Design of a Hexagonal Columnar Mesophase in Telechelic Alternating Multicomponent Semifluorinated Polyethylene OligomersV. Percec, D. Schlueter, and G. UngarView Author Information The W. M. Keck Laboratories for Organic Synthesis, Department of Macromolecular Science, Case Western Reserve University, Cleveland, Ohio 44106-7202 Department of Engineering Materials and Center for Molecular Materials, University of Sheffield, Sheffield S1 4DU, U.K. Cite this: Macromolecules 1997, 30, 3, 645–648Publication Date (Web):February 10, 1997Publication History Received27 August 1996Revised13 November 1996Published online10 February 1997Published inissue 1 February 1997https://doi.org/10.1021/ma961285wCopyright © 1997 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views333Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (190 KB) Get e-AlertsSUBJECTS:Copolymers,Organic reactions,Polymers,Radical polymerization,Transfer reactions Get e-Alerts

Boratabenzene Zirconium Complexes

1-Substituted boratabenzenes (1) are six π-electron aromatic anions which can serve as surrogates for cyclopentadienyl in important organometallic compounds. The reaction of 1 with ZrCl4 produces bis(boratabenzene) zirconium(IV) dichlorides 3, which when activated by excess methylaluminoxane react with ethylene to produce either high molecular weight polyethylene or smaller ethylene oligomers, depending upon the substituents at boron. The reaction of 3 with BuLi in the presence of PMe3 affords the corresponding zirconium(II) complexes (4). The reaction of 4 with acetylene involves an unprecedented ring annulation to afford complexes which contain the novel ligand lOH-5-boratanaphthalene.

Chain End Contribution in Static Secondary Ion Mass Spectrometry of Oligomeric Polyethylene glycols

Chain End Contribution in Static Secondary Ion Mass Spectrometry of Oligomeric Polyethylene glycols

On the morphology and crystallization kinetics of monodisperse polyethylene oligomers crystallized from the melt

The melt crystallization of three monodisperse paraffins, C 294H 590, C 246H 494 and C 198H 398, has been studied optically as a function of temperature. In both C 294H 590 and C 246H 494, a distinct minimum in the rate of crystal growth has been observed, corresponding to a transition from predominantly chain-extended crystallization at high temperatures to the growth of crystals in which the molecules adopt a once-folded conformation. This change in molecular conformation is accompanied by a change in optical texture. Well below the minimum, morphologies, are spherulitic and closely resemble polyethylene. When crystals contain chain-extended molecules, highly birefringent, coarse lamellar textures develop. In C 198H 398, no minimum in the crystal growth rate has been observed; this system does, however, exhibit similar morphological trends to those seen in C 294H 590 and C 246H 494.

Charakterisierung oligomerer Ethylenoxidaddukte mit SFC / Characterisation of Oligomer Ethylene Ox- Be AdGLcS DV OF

SFC is used to characterise polyethylene glycols, alkyl polyethylene glycolethers and alkylaryl polyethylene glycolethers with regard to their polymerhomologous distribution by means of specially prepared reference substances. These reference materials allow the determination of the peaks of the corresponding distribution chromatograms. SFC can be used for fingerprint characterisation of oligomer polyethylene oxide adducts as well as for the determination of molar masses of homologous mixtures, as it is shown for PEG 600.

Complexation of europium using polyethylene carboxylic acid

Competitive complexation of europium(III) carboxylates by an octadecanoic carboxylate and a terminally functionalized oligomeric ethylene carboxylate ( M n = ∼ 1500–2000) showed that there was little difference between a low molecular weight alkyl carboxylate ligand and an oligomeric polyethylene carboxylate ligand in their interaction with a metal salt in a toluene solution at 105°C. The most significant difference between these two carboxylate ligands was the facility with which the oligomeric carboxylate removes europium(III) from solution when the oligomer and octadecanoate were present at comparable concentrations. Comparison of calculations and experimental values for the amount of europium left in solution after equilibration of various ratios of terminally carboxylated oligomeric polyethylene and octadecanoic acids with europium(III) was used to evaluate the relative ligating ability of a soluble macromolecular and octadecyl carboxylate for europium(III) in toluene. Use of a less well-defined oxidized polyethylene instead of well-characterized terminally carboxylated oligomers as ligands had little effect on these equilibria. Experiments also showed that the solubility of these oligomerically ligated europium salts changed significantly over a temperature range of 60–85°C.

Solvation of cobalt salts by oligomeric polyethers

Polyether-salt systems involving CoBr 2 dissolved in oligomeric polyethylene glycol (PEG) and polytetramethylene glycol (PTMG) have been investigated. Both systems demonstrated conductivity maxima as a function of salt concentration. PTMG electrolytes had dramatically lower conductivities (σ max ≈ 3.6 × 10 −7 S cm −1 for PTMG, σ max ≈ 1.45 × 10 −5 S cm −1 for PEG at room temperature) which can be explained on the basis of spectral data which indicate the existence of predominantly neutral species in PTMG. The reason for the difference in the types of species present in PEG and PTMG can be rationalized on the basis of the chelate effect.

A-B-A Triblock and (A-B)nSegmented Block Copolymers of Styrene and Ethylene Oxide via Thermal Iniferters

Abstract A free radical technique is described for the synthesis of tri- and multiblock copolymers of styrene and ethylene oxide through polyethylene oxide-based thermal “iniferters.” The mono- or dihydroxy-terminated oligomeric polyethylene oxides were chemically transformed to the secondary amine terminated species. Thiocarba-mylation and oxidation of the amine groups gave rise to macro- or polymeric thiuram disulfides called macro- or polymeric “iniferters,” respectively. Thermal polymerization of styrene in the presence of the macro iniferter led to the formation of their perfect triblock copolymers, with styrene forming the central block. Utilization of the polymeric iniferter, on the other hand, give rise to (A-B)n type segmented copolymers containing as many as 3 (A-B) sequences. The length of each block could be regulated by the choice of the appropriate iniferter and its relative concentration with respect to the monomer. The iniferters and the block copolymers were characterized.