Polystyrene freeze-dried from dilute solution: Tg depression and residual solvent effects

W. Zheng, S. L. Simon

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


The calorimetric glass transition temperature, Tg, was measured for both linear and cyclic polystyrenes freeze-dried from dilute solutions of 0.10, 0.05, and 0.02% of polymer by weight in benzene. Upon freeze-drying, Tg was found to be depressed by 4-15 K depending on the sample, solvent concentration, and freezing conditions. Annealing under vacuum at moderate temperatures, from 40 to 140 °C and 0.05 Torr, resulted in the shift of Tg back towards its bulk value and was accompanied by a decrease in sample weight. The data is consistent with the observed weight loss being due to residual solvent. The amount of residual solvent is a strong function of the annealing temperature and the initial freeze-drying solution concentration; exposure to vacuum at temperatures far below Tg is generally insufficient for residual solvent removal.

Original languageEnglish
Pages (from-to)3520-3527
Number of pages8
Issue number10
StatePublished - May 3 2006


  • Freeze-drying
  • Glass transition temperature
  • Polystyrene


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