Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free-volume-holes in polymers
2007
Abstract
Doppler broadening of annihilation radiation (DBAR) measurements have been performed in uniaxially hot-drawn poly(methylmethacrylate) (PMMA) samples. An anisotropy of the free volume holes (FVHs) has been detected by measuring the deformed samples at the stretching and transverse directions and also as a function of the orientation angle (0 degrees-90 inverted perpendicular) with respect to the stretching direction.
The momentum distribution of p-Ps was calculated as a function of the potential well size and depth and compared with experiment.