title: Structural characterization of poly(diethylsiloxane) in the crystalline, liquid crystalline and isotropic phases by solid-state 17O NMR spectroscopy and ab initio MO calculations.
abstract: The structure of poly(diethylsiloxane) (PDES) has been characterized using solid-state NMR of (17)O. The sample studied had a weight-average molecular weight of 2.45 x 10(5). The sample was prepared by utilizing the cationic ring-opening polymerization of (17)O-enriched hexacyclotrisiloxane. Solid-state NMR of (17)O-enriched PDES was measured on the low-temperature beta(1) phase, the high-temperature beta(2) phase, the two-phase system consisting of the liquid crystal and isotropic liquid phase and the isotropic phase. From these data, the molecular structure and dynamics of PDES in the various phases were characterized via the chemical shifts of (17)O, and electric field gradient parameters were determined from NMR and ab initio molecular orbital (MO) calculations. In addition to the solid-state NMR of (1)H, (13)C and (29)Si previously reported on these samples, knowledge of the dynamic behavior of PDES as inferred from the NMR of (17)O in the present study was enhanced significantly. Further, the potential of combining the experimental NMR of (17)O with ab initio MO calculations to characterize the dynamics of polymers containing oxygen is demonstrated.
authors.affiliation: Department of Chemistry and Materials Science, International Research Center of Macromolecular Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kimura
authors.forename: Sho
authors.initials: S
authors.lastname: Kanesaka
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kuroki
authors.forename: Isao
authors.initials: I
authors.lastname: Ando
authors.forename: Atsushi
authors.initials: A
authors.lastname: Asano
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Kurosu
mesh_terms: D003198:Computer Simulation; D003461:Crystallography / Q000379:methods*; D004129:Dimethylpolysiloxanes / Q000032:analysis* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D008968:Molecular Conformation; D010100:Oxygen / Q000032:analysis* / Q000737:chemistry*; D010103:Oxygen Isotopes; D044367:Phase Transition; D012828:Silicones / Q000032:analysis* / Q000737:chemistry*; D012996:Solutions
chemical_list: D004129:Dimethylpolysiloxanes; D010103:Oxygen Isotopes; D012828:Silicones; D012996:Solutions; C013830:baysilon; D010100:Oxygen