title: Ideal polyethylene nanocrystals.
abstract: The water-soluble catalyst precursor [[(2,4,6-(3,5-(CF3)2C6H3)3-C6H2)-N═C(H)-(3-(9-anthryl)-2-O-C6H3)-κ(2)-N,O]Ni(CH3)(TPPTS)] (TPPTS = tri(sodiumphenylsulfonate)phosphine) polymerizes ethylene to aqueous dispersions of highly ordered nanoscale crystals (crystallinity χ(DSC) ≥ 90%) of strictly linear polyethylene (<0.7 methyl-branches/1000 carbon atoms, Mn = 4.2 × 10(5) g mol(-1)). SAXS in combination with cryo-TEM confirms this unusually high degree of order (χ(SAXS) = 82%) and shows the nanoparticles to possess a very thin amorphous layer on the crystalline lamella, just sufficient to accommodate a loop, but likely no entanglements. This ideal chain-folded structure is corroborated by annealing studies on the aqueous-dispersed nanoparticles, which show that the chain can move through the crystal as evidenced by lamella thickening without disturbing the crystalline order as concluded from an unaltered low thickness of the amorphous layers. These ideal chain-folded polyethylene nanocrystals arise from the crystallization in the confined environment of a nanoparticle and a deposition of the growing polymer chain on the crystal growth front as the chain is formed by the catalyst.
authors.affiliation: Chair of Chemical Materials Science, Department of Chemistry, University of Konstanz, Universitätsstr. 10, D-78457 Konstanz, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Osichow
authors.forename: Christian
authors.initials: C
authors.lastname: Rabe
authors.forename: Karsten
authors.initials: K
authors.lastname: Vogtt
authors.forename: Theyencheri
authors.initials: T
authors.lastname: Narayanan
authors.forename: Ludger
authors.initials: L
authors.lastname: Harnau
authors.forename: Markus
authors.initials: M
authors.lastname: Drechsler
authors.forename: Matthias
authors.initials: M
authors.lastname: Ballauff
authors.forename: Stefan
authors.initials: S
authors.lastname: Mecking