Question

What is the free volume of polystyrene at 100 °C? What experimental or theoretical evidence supports your conclusion?

Answer 1

Free volume of polystyrene at 100^oC is 0.92 cm³/gm.

Positron Annihilation experimental Techniques can measure the free volume of the polystyrene.

This technique carried out by using radioactive ²²Na as a positron source with high kinetic energy. Ii is placed into a solid the fast positrons slow down within picko second and excitatate the molecules. The implantation profile of the positrons mainly is the exponentially decreasing function as exp(-αa) where α = 42 cm-1 which is the positron absorption coefficient and a is the depth where the positron is stopped. The thin polymer foils may be stacked to obtain the required thickness of sample.