Polymer nanocomposites which have one or more nano-dimensional phases dispersed in polymer matrix show enhancement in bulk physical properties. In order to achieve the desired properties, a large number of polymer nanocomposites have been prepared by choosing different polymers and nanofillers. These studies showed that interfacial interaction between polymer molecules and nanofillers is the most important factor to achieve the synergistic effect towards enhancement in the bulk physical properties. The strong interfacial interaction also promotes the fine dispersion of nanofillers in a polymer matrix which consequently enables the preparation of polymer nanocomposites with higher loading of nanofillers. The polymer matrix constitutes a large volume fraction of polymer nanocomposites and hence the molecular packing of the polymer matrix itself plays a deterministic role in governing the physical properties of the nanocomposites. The strong interfacial interaction brings severe changes in the original molecular packing. In order to establish the structure-property relationships for polymer nanocomposites, characterization of molecular packing of polymer matrix in its nanocomposites is essential. In this aspect positron annihilation lifetime spectroscopy (PALS) is a highly suitable technique for characterization of free volume holes in polymers or polymer nanocomposites. The present review briefly describes the positron annihilation lifetime spectroscopy technique and relevant models for calculations of free volume hole’s size, density and their size distribution in polymer nanocomposites. We present a summary of the recent studies focussed on investigation of free volume structure (molecular packing) of polymer nanocomposites using PALS and its impact on transport, thermal and mechanical properties of the nanocomposites.

具有分散在聚合物基质中的一个或多个纳米相的聚合物纳米复合材料显示出整体物理性质的增强。为了获得所需的性能，已经通过选择不同的聚合物和纳米填料制备了大量的聚合物纳米复合材料。这些研究表明，聚合物分子与纳米填料之间的界面相互作用是实现增强整体物理性能的协同效应的最重要因素。强烈的界面相互作用还促进了纳米填料在聚合物基质中的精细分散，从而使得能够制备具有更高纳米填料填充量的聚合物纳米复合材料。聚合物基质构成聚合物纳米复合材料的大体积分数，因此聚合物基质本身的分子堆积在控制纳米复合材料的物理性质中起决定性作用。强烈的界面相互作用带来了原始分子堆积的严重变化。为了建立聚合物纳米复合材料的结构-性质关系，表征聚合物基质在其纳米复合材料中的分子堆积是必不可少的。在这方面，正电子an灭寿命光谱法（PALS）是一种非常合适的技术，用于表征聚合物或聚合物纳米复合材料中的自由体积孔。本综述简要描述了正电子an没寿命谱技术和用于计算自由体积孔尺寸的相关模型，聚合物纳米复合材料的密度和尺寸分布。我们提供了最近研究的摘要，重点是研究使用PALS的聚合物纳米复合材料的自由体积结构（分子堆积）及其对纳米复合材料的运输，热和机械性能的影响。