Eur. Phys. J. E 8, 201-207 (2002)
Effects of entanglement concentration on and local segmental motionsP. Bernazzani1, S.L. Simon1, D.J. Plazek2 and K.L. Ngai3
1 Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409-3121, USA
2 Department of Materials Science and Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA
3 Naval Research Laboratory, Washington, DC 20375-5320, USA
(Received 15 August 2001 and Received in final form 2 March 2002)
The process of spin-coating to fabricate thin polymer films with high molecular weight can produce samples with entanglement concentrations that are far below the equilibrium value. It is not clear whether or not such low entanglement concentrations are responsible for the depression of the glass temperature in thin polymer films. In this work, we measure the calorimetric glass temperature and viscoelastic response of polystyrenes with molecular weights ranging from to g/mol, for both bulk material and for samples freeze-dried from dilute solution. We conclude that the reduction of the glass temperature observed in thin polymer films cannot be due to the reduced entanglement concentration in the samples.
64.70.Pf - Glass transitions.
68.60.Bs - Mechanical and acoustical properties.
62.20.Hg - Creep.
65.20.+w - Thermal properties of liquids: heat capacity, thermal expansion, etc..
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002