Molecular probe dynamics and free volume in glass-formers: 1,2- and 1,4-poly(butadiene)s

- Spin probe TEMPO dynamics in 1,2- and 1,4 poly(butadiene)s measured by ESR.
- Ortho-positronium (o-Ps) annihilation studies performed by PALS.
- The opposite T50G/Tg < 1 and T50G/Tg > 1 ratios found.
- Almost constant o-Ps lifetime at T50G transition independently of physical state.
- Free volume fluctuation as a controlling factor of T50G transition.