Influence of entanglements on glass transition of atactic polystyrene
Abstract
Freeze-dried samples were prepared from dilute solutions of atactic polystyrene (a-Ps) in benzene in a concentration range of 1 × 10−1 to 2 × 10−5 g/mL, and their glass transition temperatures (Tg) were determined by differential scanning calorimetry. It was found that below a critical concentration (C), the Tg of samples decreases linearly with decreasing logarithmic concentration of solutions. The freeze-dried samples were annealed at a constant temperature for various times or at various temperatures for the same period of time. The Tg of samples prepared from solutions of concentration below C was observed to shift to higher temperature with increasing annealing temperature or annealing time, finally approaching that of the bulk sample. Fourier transform infrared (FTIR) spectra of the freeze-dried samples were determined and were compared with the bulk sample. Significant changes in line width and absorption intensity were observed in the spectra of the freeze-dried samples, indicating that the packing of segments is in a more dilatant state. During annealing, the packing of segments in the samples gradually approaches that of the bulk sample, diminishing the differences in FTIR spectra between the freeze-dried sample and the bulk sample. The experimental observations are discussed, and it is assumed that intrachain and interchain entanglements may play an important role in glass transition.
- Publication:
-
Journal of Polymer Science B Polymer Physics
- Pub Date:
- August 2005
- DOI:
- 10.1002/polb.20513
- Bibcode:
- 2005JPoSB..43.2243R