Free volume and microscopic dynamics in amorphous polymers

The free-volume microstructure in three amorphous polymers cis-1, 4-polybutadiene (PBD), polyisobutylene (PIE) and atactic polypropylene (a-PP) has been studied by positron annihilation spectroscopy via the annihilation characteristics of ortho-positronium, lifetime tau(3) and relative intensity I-3. Simultaneously, the local chain dynamics has been studied by neutron scattering. The temperature coefficients of hole size below and above T-g are comparable with those of mean-square displacements indicating that the free-volume hole expansion is governed by the microscopic chain mobility. In addition, the relative intensity anomalies in simple polymers (PBD, PIE) are related to the onset of the fast process. This is a structural indicator for the course of fast process.