Free Volumes of Ploymers Studied by Positron Annihilation

采用正电子湮没寿命（PAL）技术研究了四种环氧树脂（甲酚（CR）、三羟基苯基甲烷（THPM）、四甲基双酚（TMB）和双酚A (BA)）的分子间空穴与吸水性的关系。根据邻正电子离子（o-Ps）的寿命（tau_3）来测量空穴的大小。由于THPM比其他样品具有更大的tau_3值（即更大的分子间空穴）和吸收率，因此tau_3与吸收率之间的相关性已被证明是明显的。假设一个非常简化的模型，使用分子动力学的计算机代码计算最小单元胞的孔的形状；发现THPM的形状与其他三个样品的形状不同。用正电子湮没寿命（PAL）技术研究了双酚-A双氰酸酯（BADCy）的聚合过程。在此过程中，BADCy通过加热形成三嗪环进行固化；从室温下的粉末，到熔点以上的液体，再到高温固化后的固体。研究表明，聚乳酸是研究连续聚合过程微观结构变化和状态转变的有力手段。

A positron-annihilation lifetime (PAL) technique was applied to four kinds of epoxy resin (cresol novolac (CR), tris-hydroxy-phenyl-methane (THPM), tetra-methyl-biphenol (TMB) and bis-phenol A (BA)) in order to study the relation between the intermolecular space holes and water absorption. The size of the holes was measured based on the lifetime (tau_3) of the ortho-positronium (o-Ps). Since THPM has a larger tau_3 value (hence, a larger intermo-lecular-space hole) and absorption rate than that of the other samples, the correlation between tau_3 and the absorption rate has been shown to be evident.Assuming a very simplified model, the shapes of the holes for the smallest unit cell were calculated using a computer code of molecular-dynamics ; the shape for THPM was found to be different from those of the other three samples.A polymerization process of Bisphenol-A dicyanate (BADCy) has been studied by a positron annihilation lifetime (PAL) technique. In the process, BADCy was cured through triazine ring formation by heating ; the state changed from a powder at room temperature, through a liquid above the melting point, to a solid after curing at high temperatures. It has been shown that PAL is a powerful technique for studying microscopic structure changes and the state transition of the continuous polymerization process.