; Wei Long
; Zhang Tianbao] Acad Sinica, Inst High Energy Phys, Lab Nucl Anal Tech, Beijing 100080, Peoples R China
; [He Liu
; Zhang Shufan
; Qi Zongneng] Acad Sinica, Inst Chem, Beijing 100080, Peoples R China
The results of positron annihilation studies on the side-chain polymer liquid crystals were obtained as a function of temperature. It is indicated that thermotropic liquid crystal has two phase transition points near 40 degrees C and 76 degrees C respectively. It is suggested that the first phase transition point is correspondent to the melting point of specimen and the second one is clearing point at which liquid crystal phase transits isotropic liquid phase. It can be concluded by the changes of Free-Volume at the phase transition points that the smectic state S-A is in better ordered state than the other liquid crystals. The difference in the curves of o-Ps life-time with temperature between the liquid crystal and the liquid crystal polymer was explained.