Free volumes and occupied volumes in oligomeric polypropylenglycols

It is shown that combined use of positron annihilation lifetime spectroscop y-an experimental tool to investigate the intermolecular sub-nanometric spa ces (free volume) in amorphous polymer-and of specific-volume measurements supplies unique information on the occupied volume, allowing one to study i ts behavior under variation of thermodynamic quantities. In the present cas e thermal expansion is considered. The methodology has been applied to two members of a homologous series of polypropyleneglycol oligomers; however, i t can be used in principle to any disordered macromolecular structure and l iquids.