title: Characterization of a model Phillips catalyst by mass spectrometry.
abstract: A model Phillips catalyst for ethylene polymerization, prepared by spin coating a Cr(III)(Cr(acac)3) precursor on a silicon wafer, was submitted to an oxidative activation. Laser ablation Fourier transform mass spectrometry provided direct information on molecular species at the silicon wafer surface during activation. At 350 degrees C the chromium precursor was degraded, while chromium oxide species were formed. The chromium concentration decreased with temperature. The activated model catalyst was active for ethylene polymerization. Using complementary techniques (Fourier transform infrared spectroscopy, laser desorption/ionization mass spectrometry), the polymer was identified as crystalline polyethylene. After 1 h of polymerization at 160 degrees C, dome-like structures were observed by atomic force microscopy. Their morphologies were constituted of regions of parallel aligned lamellae of polymer.
authors.affiliation: Unité de catalyse et de chimie des matériaux divisés, Université catholique de Louvain, Croix du Sud 2/17, B-1348 Louvain-la-Neuve, Belgium. dicroce@cata.ucl.ac.be
authors.forename: Pascal Gabriel
authors.initials: PG
authors.lastname: Di Croce
authors.forename: Frédéric
authors.initials: F
authors.lastname: Aubriet
authors.forename: Rachel
authors.initials: R
authors.lastname: Chéty-Gimondo
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Muller
authors.forename: Paul
authors.initials: P
authors.lastname: Grange
mesh_terms: D002384:Catalysis; D003460:Crystallization; D005030:Ethylenes / Q000032:analysis / Q000737:chemistry*; D018625:Microscopy, Atomic Force / Q000379:methods; D008956:Models, Chemical; D020959:Polyethylene / Q000032:analysis; D011108:Polymers / Q000032:analysis / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013499:Surface Properties
chemical_list: D005030:Ethylenes; D011108:Polymers; D020959:Polyethylene; C036216:ethylene