在当今的生产和生活中，高分子材料应用广泛。高分子材料常见的加工过程（如吹膜、挤出）都会使得高分子材料经历显著的非线性形变。高分子材料在加工过程中常以熔体的状态存在，这种状态兼具液体的流动与固体的形变特征，并具有丰富的时间层级，为深入理解材料的行为带来挑战。高分子体系中链间会形成缠结，并显著影响体系的流变行为。缠结是高分子动力学的核心概念，也是高分子丰富流变行为的微观基础。研究非线性形变下高分子熔体中缠结的行为，不仅是高分子物理理论研究的重要课题，对高分子材料的工业加工也具有一定的指导意义。本论文旨在非线性拉伸情况下，明确形变高分子中缠结的微观图像，并在实验层面给出缠结运动的微观证据，定量研究形变高分子体系中微观缠结的演变及其对体系宏观流变行为的影响。论文利用分子动力学模拟方法，系统进行了多工况、多分子量的拉伸模拟，并对现有的拓扑分析方法在形变情况下的适用性进行了探索和改进。结果表明，形变使得体系中的缠结不再等同，需要关注与宏观形变一致的缠结。通过分析模拟数据，根据形变后对拉伸应力的贡献，提出了有效缠结的概念。基于有效缠结的定义，定量考察了松弛过程中缠结的演化，对长期缺乏良好定义的约束释放过程进行了定量描述。基于管道模型的框架，对体系的应力松弛过程给出了良好的预测，揭示了松弛过程中各个阶段起主导作用的微观机理，及其对应的时间特征。通过考察有效缠结的演化，观察到了约束释放过程导致的有效缠结与应力松弛的?−1/2幂律，揭示了这一过程的微观机理。通过追踪有效缠结的演化，观察到有效缠结通过链端离开释放的微观过程，有效缠结分布的衰减很好地描述了管段存活概率函数，与管道模型的物理图像一致。针对形变体系中缠结的运动和演化长期以来难以利用实验从微观层面考察的问题，基于有效缠结的概念，论文提出了一个描述形变高分子体系的物理模型，发展了一套分析小角中子散射数据的分析方法，并在模拟数据中进行了充分的验证。利用模型对一组实验的小角中子散射谱进行分析，定量得到了松弛过程中构象的形变和有效缠结的演化，同样发现了约束释放过程导致的松弛过程中有效缠结松弛的?−1/2 幂律。模型的拟合参数对应力松弛给出了良好的预测。

Polymeric materials are widely applied in modern industry and daily life. Common processing techniques such as blown film and extrusion subject these materials to significant nonlinear deformations. During processing, polymers typically exist in a melt state that exhibits both the flow characteristics of liquids and the deformation properties of solids, spanning a wide range of time scales and thereby complicating the understanding of their behavior. Chain entanglements, which form within polymer systems, profoundly influencing their rheological behavior. As a fundamental concept in polymer dynamics, entanglements serve as the microscopic basis for the complex rheological behavior of polymeric materials. Investigating the behavior of entanglements in polymer melts under nonlinear deformations is not only a pivotal issue in theoretical polymer physics but also provides practical guidance for the industrial processing of these materials.This work aims to elucidate the microscopic picture of entanglements in deformed polymers under nonlinear extensional conditions and to provide experimental evidence of entanglement dynamics. It quantitatively investigates the evolution of microscopic entanglements in deformed polymer systems under nonlinear extensional conditions and to elucidate their impact on the macroscopic rheological behavior. This study employs molecular dynamics simulations to investigate tensile deformation under multiple conditions and molecular weights. Additionally, the applicability of existing analytical methods under deformation is explored and refined. The results indicate that deformation alters the entanglement structure in the system, necessitating a focus on entanglements that align with the macroscopic deformation.Analysis of the simulation data—specifically, the contributions to the extensional stress induced by deformation led to the introduction of the concept of “effective entanglement.” Based on this concept, the evolution of entanglements during the relaxation process was quantitatively examined, and a comprehensive description of the constraint release process—previously lacking a precise definition—was provided. Within the framework of the tube model, the stress relaxation process of the system was accurately predicted, revealing the dominant microscopic mechanisms at each stage of relaxation and their associated time scales. Furthermore, by tracking the evolution of effective entanglements, a t^-1/2 power-law of the relaxation of effective entanglement and stress induced by constraint release, was observed, thereby unveiling the underlying microscopic mechanism. In addition, monitoring the evolution of effective entanglements revealed that their relaxation is governed by a microscopic process in which chain ends disengage, with the decay of the effective entanglement distribution accurately capturing the survival probability of the tube segments, which is consistent with the physical picture provided by the tube model.To address the long-standing experimental challenge of directly probing entanglement dynamics and evolution at the microscopic level in deformed polymeric systems, this dissertation proposes a physical model for deformed polymer systems based on the concept of effective entanglement. It also develops a methodology for analyzing small-angle neutron scattering （SANS） data, which has been thoroughly validated using simulation data. Application of the model to a set of experimental SANS spectra allowed for the quantitative determination of chain conformation deformation and the evolution of effective entanglements during the relaxation process, with the t^-1/2 power-law behavior induced by constraint release also observed in the relaxation of effective entanglements. The model parameters thereby offer reliable predictions of the rheological behavior.