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Small angle neutron scattering (SANS) studies of diffusion in bulk polystyrene near the glass transition temperature (T g )
Author(s) -
Anderson James E.,
Jou J.H.
Publication year - 1988
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19880150127
Subject(s) - glass transition , annealing (glass) , polystyrene , materials science , neutron scattering , scattering , small angle neutron scattering , polymer , deuterium , analytical chemistry (journal) , diffusion , thermal diffusivity , crystallography , thermodynamics , molecular physics , chemistry , optics , nuclear physics , physics , chromatography , composite material
Ultraslow diffusion in bulk polymers has been measured by SANS. The experiment begins by measuring scattering from heterogeneous specimens containing domains of protonated‐and deuterated‐polymers at temperatures far below T g . The samples are subsequently held [annealed] above T g for a known time‐interval, then cooled below T g where SANS is measured again. Scattering changes, from before to after annealing, are analysed to obtain diffusion coefficients. The recent Summerfield ‐ Ullman procedure is used to deconvolute portions of the scattering curve that decrease and increase with annealing time. Because of SANS sensitivity to small distances, the method yields D ≈ 10 −18 to 10 −15 cm 2 /s after annealing times of 1–24 h. Data analysis is complicated by “smearing effects” which produce apparent Q‐dependent diffusion coefficients. Representative experimental results on polystyrene at 108°–130°C are discussed.