Investigation of the Temperature Dependence of Free Volume in Polymethylpentene by Positron Annihilation Method

Positron lifetime measurements in polymethylpentene were performed in a wide temperature range. A conventional fast-slow coincidence lifetime spectrometer with plastic scintillators was used. All the measurements were made in vacuum. Additional measurements (X-ray diffraction, differential scanning calorimetry, and mechanical spectroscopy) were also performed to establish properties of samples. Mean free volume radii in the investigated samples were estimated from the positron lifetimes measurements results. An increase in I$\text{}_{3}$ with the elapsed time of measurements was observed