Premium
Thermal expansion and contraction of polymer thin films
Author(s) -
Kanaya T.,
Miyazaki T.,
Inoue R.,
Nishida K.
Publication year - 2005
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200460378
Subject(s) - thermal expansion , materials science , negative thermal expansion , thin film , radius of gyration , glass transition , annealing (glass) , polymer , composite material , neutron scattering , silicon , scattering , condensed matter physics , optics , nanotechnology , optoelectronics , physics
We have studied thermal expansion and contraction of polystyrene thin film supported on silicon substrate using X‐ray reflectivity and inelastic neutron scattering techniques. In annealing experiments, we found fast and very slow contraction processes in the thin films above the glass transition temperature. The fast one was attributed to normal relaxation (annealing) process observed in bulk and responsible partly for the reported apparent negative expansivity. In addition, we found extremely slow re‐expansion process in the glassy state. The ultra‐slow contraction and re‐expansion have been assigned to the lateral expansion and contraction of the film, respectively. Using well‐annealed films, we have evaluated thermal expansivity as a function of film thickness, and found that it decreases with film thickness in a thickness range below twice of radius of gyration of a polymer chain 2 R g in the glassy state. The decrease has been attributed to hardening of harmonic force constant due to confinement in a thin film. This idea was confirmed in the inelastic neutron scattering measurements. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)