目的 利用分子动力学分析聚丙烯(PP)活性包装材料内百里香酚(THY)和香芹酚(CAR)的扩散机理。方法 建立含有THY和CAR的等规、间规和无规3种PP构象的元胞模型，从均方位移角度研究THY、CAR的扩散行为，从溶解度参数、相互作用能、运动轨迹、自由体积角度探索THY、CAR的扩散机理。结果 随着温度升高，THY、CAR在PP中的扩散系数增大，元胞的自由体积分数(FFV)增大，同时THY、CAR的运动轨迹范围扩大，由一个团簇逐渐形成多个团簇。在不同构象的PP中，THY、CAR的扩散系数随着PP结晶度的增加而降低，元胞的FFV随着PP结晶度的增加而增大。在相同温度、相同构象的PP中，PP与THY的相容性优于CAR，含THY元胞的FFV小于含CAR元胞的FFV，即PP对THY扩散运动的阻碍作用大于CAR，在扩散系数上体现为THY小于CAR。THY、CAR和PP的相互作用能差异不大，且相互作用能几乎由范德华力贡献。结论 活性剂在PP中的扩散受多个因素影响，温度、活性剂结构、基材结构以及活性剂与基材的相容性均影响扩散，其中温度是影响扩散的主要因素，活性剂结构、基材结构以及活性剂与基材的相容性是影响扩散的次要因素。

The work aims to conduct molecular dynamics simulation to investigate the diffusion mechanisms of thymol (THY) and carvacrol (CAR) in polypropylene (PP) active packaging materials. The unit cell models of isotactic, syndiotactic and atactic PP matrices including THY and CAR were established to study the diffusion behaviors of THY and CAR from the perspective of mean squared displacement and the diffusion mechanisms of THY and CAR were explored from encompassing solubility parameters, interaction energies, movement trajectories, and free volume. The results showed an increase in the fraction of free volume (FFV) of the unit cells, an enhancement in the diffusion coefficients and an expansion of the movement trajectories of THY and CAR with the increase of temperature, facilitating the transformation from a single cluster to multiple clusters. When the THY and CAR were in various PP matrices, the diffusion coefficients of them decreased as the crystallinity increasing, whereas the FFV of the unit cells raised with higher crystallinity. While when they were in the same matrices, PP had a better compatibility with THY than CAR, and the FFV of THY unit cell was smaller than that of the CAR unit cell. Additionally, the interaction energies of THY, CAR and PP did not differ much and the interaction energy was almost contributed by van der Waals forces. Thus, it can be concluded that the diffusion of active agents in packaging materials is influenced by multiple factors, including temperature, the structure of the active agent, the structure of the material, and the compatibility between the active agent and the material, and temperature can remarkably influence the diffusion while the other factors exhibit insignificant effect.