Change in free volume of polyvinylidene fluoride

Measurement of positron lifetime was carried out on polyvinylidene fluoride as a function of temperature ranging from 193 to 293 K. The local molecular motion, the cooperative motion of long chain, and the thermal expansion are discussed based on the change in free volume concluded with the use of positron lifetime. The different temperature dependence of motions is suggested for an amorphous area constrained by crystalline regions and a free amorphous area.