液晶相变的微结构研究

用正电子湮没和差示扫描量热(DSC)变温测量液晶(EBBA)样品的正电子湮没寿命谱及DSC曲线,结果表明正电子湮没的短寿命(τ_s)基本不变,而长寿命(τ₁)和强度(I₁)明显地有两次跳变,其跳变的温度范围与DSC所测定的相转变温度范围基本一致,在加热和冷却过程中样品在晶体相←→向列相之间的相互转变的相转变温度范围显著不同。用正电子湮没的ORE模型讨论了由于液晶相转变所引起的微结构变化,从而提出正电子是研究液晶(EBBA)相变的探针。 关键词：

A STUDY ON MICROSTRUCTURE OF PHASE TRANSITION IN A LIQUID CRYSTAL

The positron lifetime and DSC measurements for EBBA have been made with heating and cooling clycles. The experimental results show that the shorter lifetime (τ_s) is essentially independent of temperature while the longer lifetime (τ₁) and the intensity (I₁) change abruptly twice with temperature. These two critical temperatures are in accordance with "he transition temperature measured by the DSC. In the heating and cooling clycles the transition temperature are different. The changes in microstructure during the phase transition have been explained by the ORE model of positron annihilation, which raised the idea that positron can be a probe in the study of EBBA phase tyansitioa