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Displaying 51 - 68 of 68

Morphological Partitioning of Ethylene Defects in Random Propylene-Ethylene Copolymers

August 1, 2000
Author(s)
R G. Alamo, David L. VanderHart, Marc R. Nyden, L Mandelkern
A series of four propylene/ethylene, metallocene-catalyzed copolymer samples, with ethylene mole fractions ranging from 0.8 to 7.5 mol % and melt-crystallization histories of cooling at 1 C/min, were studied by 13C solid state NMR techniques. The principal

Observation of Resonances Associated With Stereo and Regio Defects in the Crystalline Regions of Isotatic Polypropylene: Towards a Determination of Morphological Partitioning

August 1, 2000
Author(s)
David L. VanderHart, R G. Alamo, Marc R. Nyden, M S. Kim, L Mandelkern
We report defect-resonance patterns associated with 2 kinds of low-concentration defects typically found in metallocene-synthesized isotactic polypropylenes (iPPs). These defects are the simple mrrm stereo defect and the regio 2,1-erythro defect. This work

Determination of the Molecular Mass Distribution of Narrow Polydispersity Polystyrene by MALDI-TOF-MS: Interlaboratory Comparison

March 1, 2000
Author(s)
Kathleen M. Flynn, S Wetzel, William E. Wallace, William R. Blair, R J. Goldschmidt, David L. VanderHart, B M. Fanconi
NIST has sponsored a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) interlaboratory comparison using a well-characterized polystyrene to determine the reproducibility in determining the molecular mass

C30 Self-Assemblied Monolayers on Silica, Titania, and Zirconia: HPLC Performance, Atomic Force Microscopy, Ellipsometry, and NMR Studies of Molecular Dynamcis and Uniformity of Coverage.

January 1, 2000
Author(s)
David L. VanderHart, Lane C. Sander, Xiaohong Gu, Tinh Nguyen, Stephen A. Wise, M Pursch, D A. Gajewski
C30 self-assembled monolayers (SAMs) have been prepared on zirconia, titania and two different silica gels by reacting C30 trichlorosilane with the humidified surfaces. 13 deg C solid-state NMR spectroscopy indicated higher alkyl chain order on titania and

Comparison of Classical and MALDI-TOF-MS Analysis of a Polystyrene Interlaboratory Sample

January 1, 1999
Author(s)
William R. Blair, B M. Fanconi, R J. Goldschmidt, Charles M. Guttman, William E. Wallace, S Wetzel, David L. VanderHart
Over the past several years, the use of MALDI-TOF-MS for analysis of synthetic polymers has increased significantly. As the number of polymer analyses by MALDI has increased, scrutiny of the MALDI results in comparison to classically derived values for Mw