Abstract
Changes in the distribution of local free volume in polystyrene glass during physical aging were measured by using photochromic probe molecules requiring different amounts of volume to photoisomerize. The fraction of local free volume in the size range 130-180 Å3 is constant as the polystyrene molar weight decreases to a critical value between 34 000 and 92 000. At lower molar weights the fraction of local free volume in the size range 130-280 Å3 decreases with decreasing molar weight. Physical aging in polystyrene glass reduces or leaves unchanged the fraction of local free volume larger than each probe needs to isomerize. During physical aging the greatest loss of local free volume occurs in the size range larger than 280 Å3, but the amount of loss varies with annealing temperature. The temperature of maximum rate of loss is 20-25 °C less than Tg for polystyrene of 3970 and 9050 molar weight. In polystyrene of 573000 molar weight annealed 250 h at 30 °C, most of the loss of local free volume larger than 280 Å3 occurs within the first 4 h.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3490-3497 |
| Number of pages | 8 |
| Journal | Macromolecules |
| Volume | 21 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 1 1988 |
ASJC Scopus subject areas
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry