Molecular dynamics and free volume in organic glass-formers: A series of oligomer and polymer 1,4-poly(isoprene)s

We present a combined study of the rotational dynamics and free volume in a series of 1,4-poly(isoprene)s using ESR and PALS, respectively. The spectral parameter of mobility, 2Azz′, of the spin probe TEMPO is related to the annihilation of the ortho-positronium (o-Ps) probe. The o-Ps lifetime τ3(T50G) ≅ const.1 and τ3( T x 1 fast ) ≅ const.2 rules are valid independent of chain length and moreover, the T50G’s coincides with the bend effect at T b 1 L ’s. Finally, the new finding is that the first acceleration at T x 1 slow agrees with a change in the o-Ps lifetime width parameter, σ3, below the glass transition temperature.