On leave from the Malaysian University of Science, Pinang, Malaysia
Effect of dispersity on the Tll (>Tg) transition in polystyrene
Article first published online: 9 MAR 2003
Copyright © 1976 John Wiley & Sons, Inc.
Journal of Applied Polymer Science
Volume 20, Issue 5, pages 1277–1288, May 1976
How to Cite
Glandt, C. A., Toh, H. K., Gillham, J. K. and Boyer, R. F. (1976), Effect of dispersity on the Tll (>Tg) transition in polystyrene. J. Appl. Polym. Sci., 20: 1277–1288. doi: 10.1002/app.1976.070200511
- Issue published online: 9 MAR 2003
- Article first published online: 9 MAR 2003
- Manuscript Revised: 2 JUL 1975
- Manuscript Received: 12 MAR 1975
The presence of a high temperature (>Tg) relaxation in amorphous polystyrene has been investigated further. In the previous work,1 the techniques of differential thermal analysis (DTA) and torsional braid analysis (TBA) were employed to study polystyrene as a function of “monodisperse” molecular weight. The occurrence of the Tll transition appeared to be associated with the attainment of a critical viscosity level with also corresponded with a free volume level. An entanglement network developed at a critical value of molecular weight, Mc, giving a break in the Tll-versus-M plots. The present work deals with the influence of dispersity on the Tll transition, below and above Mc. A series of binary blends of “monodisperse” anionically polymerized polystyrenes with systematic changes in M̄n and heterogeneity index (M̄w/M̄n) was tested by TBA. The results show that when both components have molecular weights below Mc, single and average values of Tg and Tll are observed which are linearly related to M̄n−1, as predicted by free volume arguments. Although a single Tg is observed when one component has a molecular weight above and the other has a molecular weight below Mc, the components appear to undergo the Tll relaxation independently. The results indicate that both the glass transition and the Tll transition are basically governed by the same type of molecular motion but at different length ranges.