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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
Abstract 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.