Late-metal catalysts for ethylene homo- and copolymerization.

Precise control of polyolefin stereochemistry using single-site metal catalysts.

Theory of Raman scattering evolution and revolution of Raman instrumentation - application of available technologies to spectroscopy and microscopy Raman spectroscopy and its adaptation to the industrial environment Raman microscopy - confocal and scanning near-field Raman imaging the quest for accuracy in Raman spectra chemometrics for Raman spectroscopy Raman spectra of gases Raman spectroscopy applied to crystals - phenomena and principles, concepts and conventions Raman scattering of glass Raman spectroscopic applications to gemmology Raman spectroscopy on II-IV-semiconductor nanostructures medical applications of Raman spectroscopy - in vivo Raman spectroscopy some pharmaceutical applications of Raman spectroscopy low-frequency Raman spectroscopy and biomolecular dynamics - a comparison between different low-frequency experimental techniques collectivity of vibrational modes Raman spectroscopic studies of ion-ion interactions in aqueous and non-aqueous electrolyte solutions environmental applications of Raman spectroscopy to aqueous solutions Raman and surface enhanced resonance Raman scattering - applications in forensic science application of Raman spectroscopy to organic fibres and films applications of IR and Raman spectra of quasi-elemental carbon process Raman spectroscopy the use of Raman spectroscopy to monitor the quality of carbon overcoats in the disk drive industry Raman spectroscopy in the undergraduate teaching laboratory Raman spectroscopy in the characterization of archaeological materials.

Handbook of Raman Spectroscopy: From the Research Laboratory to the Process Line

Mechanistic studies of olefin polymerizations catalyzed by aryl-substituted α-diimine−Pd(II) complexes are presented. Syntheses of several cationic catalyst precursors, [(N∧N)Pd(CH3)(OEt2)]BAr‘4 (N∧N = aryl-substituted α-diimine, Ar‘ = 3,5-(CF3)2C6H3), are described. X-ray structural analyses of [ArNC(H)C(H)NAr]Pd(CH3)(Cl) and [ArNC(Me)C(Me)NAr]Pd(CH3)2 (Ar = 2,6-(iPr)2C6H3) illustrate that o-aryl substituents crowd axial sites in these square planar complexes. Low-temperature NMR studies show that the alkyl olefin complexes, (N∧N)Pd(R)(olefin)+, are the catalyst resting states and that the barriers to migratory insertions lie in the range 17−19 kcal/mol. Following migratory insertion, the cationic palladium alkyl complexes (N∧N)Pd(alkyl)+ formed are β-agostic species which exhibit facile metal migration along the chain (“chain walking”) via β-hydride elimination/readdition reactions. Model studies using palladium−n-propyl and −isopropyl systems provide mechanistic details of this process, which is respon...

Mechanistic Studies of Pd(II)−α-Diimine-Catalyzed Olefin Polymerizations1

Ethylene Oligomerization and Propylene Dimerization Using Cationic (α-Diimine)nickel(II) Catalysts

Fibers of poly(p-phenylene terephthalamide) (PPTA) have a fibrillar morphology, the individual fibrils having a high proportion of extended chains passing through periodic defect layers. A pleat structure is superimposed. The fibers are fully crystalline (within the limits of determination) with a small fraction of randomly oriented crystalline material. The major distinction between PPTA and conventional fibers lies in the high level of extended chains passing through the defect layers of the former structure. These extended chains result in crystallographic register being maintained between adjacent ordered zones. Quantitatively, a measure of this order is obtained from a comparison of the correlation length, obtained from meridional x-ray peak widths, and the defect spacing. In conventional fibers the defect spacing, i.e., long period, is longer than the correlation length (i.e., crystal size). In PPTA, the analog of the long period, the defect spacing (about 35 nm) is smaller than the correlation length, which is over 80 nm.

Morphology of poly(p‐phenylene terephthalamide) fibers

Structure, crystallization and morphology of poly (aryl ether ketone ketone)

Time-resolved X-ray study of poly(aryl ether ether ketone) crystallization and melting behaviour: 1. Crystallization

Time-resolved X-ray study of poly(aryl ether ether ketone) crystallization and melting behaviour: 2. Melting

A new high molecular weight aromatic polyimide has been synthesized from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 2,2′-dimethyl-4,4′-diaminobiphenyl (DMB) in p-chlorophenol at elevated temperature. BPDA-DMB fibers have been spun by a dry-jet wet spinning method. The fibers were elongated and annealed at elevated temperatures above 400°C to achieve excellent mechanical properties. In seven times drawn fibers, the BPDA-DMB molecule packs into a triclinic unit cell with dimensions of a = 2,10(2) nm, b = 1,523(8) nm, c = 4,12(7) nm, α = 61,2(6)°, β = 50,7(7)°, and γ = 78,9(6)° with the number of chain repeating units per unit cell (Z) is sixteen. After annealing at elevated temperatures, the fibers produce a small modification of the unit cell [a = 2,048(6) nm, b = 1,529(5) nm, c = 4,00(2) nm, α = 62,1(3)°, β = 52,2(3)° and γ = 79,6(3)°]. By increasing the draw ratio, both the crystallinity and crystal orientation increase. The BPDA-DMB fibers possess a decomposition temperature of 530°C in nitrogen and 500°C in air at a 5% weight loss when the heating rate is 10°C/min. After extensive drawing, BPDA-DMB fibers exhibit a tensile strength of 3,3 GPa and a tensile modulus of over 130 GPa. Dynamic mechanical behavior of the fibers show both α (glass transition) and β (sub-glass transition) relaxations above room temperature. The nature of the sub-glass transition behavior is described as a noncooperative motion attributed to the diamine portion of the molecule. The activation energy for this relaxation in as-spun fibers is 109 kJ/mol and increases to 144 kJ/mol by increasing the draw ratio. This β relaxation is found to be crystallinity dependent. The α transition is also suppressed by crystallinity which increases with draw ratio.

High performance aromatic polyimide fibers, 3. A polyimide synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2′‐dimethyl‐4,4′‐diaminobiphenyl

Kenncorwin H. Gardner

Papers

Morphology of poly(p‐phenylene terephthalamide) fibers

Structure, crystallization and morphology of poly (aryl ether ketone ketone)

Time-resolved X-ray study of poly(aryl ether ether ketone) crystallization and melting behaviour: 1. Crystallization

Time-resolved X-ray study of poly(aryl ether ether ketone) crystallization and melting behaviour: 2. Melting

High performance aromatic polyimide fibers, 3. A polyimide synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2′‐dimethyl‐4,4′‐diaminobiphenyl