Ph.D. candidate Lei Wu and colleagues, under the supervision of Professor Wei Chen, have published a research article in Analytical Chemistry entitled “Strain-Induced Accelerated Chain Dynamics in Cross-Linked Natural Rubber under Active Deformation: An in-situ Nuclear Magnetic Resonance Study.” This work focuses on the nonlinear mechanical behavior of natural rubber during uniaxial stretching and systematically elucidates the contribution mechanisms of different network components to the mechanical response, thereby deepening the molecular-scale understanding of the deformation mechanism of natural rubber.
In this study, the authors combined an in-situ stretching device with time-domain nuclear magnetic resonance (TD-NMR) to simultaneously obtain stress–strain curves and the evolution of chain dynamics of different components during deformation. In addition to observing strain-induced restrictions of chain dynamics in Region I (𝜆mac < 2.1) and Region III (𝜆mac > 3.5), they discovered anomalous strain-induced acceleration of chain dynamics for semi-restricted chains within the range 2.1 < 𝜆mac < 3.5. This strain interval coincides with the plateau region of the tensile modulus. Furthermore, variable-temperature stretching NMR measurements revealed that these critical points (𝜆mac = 2.1 and 3.5) are almost independent of stretching temperatures between 35 and 85 °C. Based on these findings, the authors proposed a strain-induced heterogeneous network deformation model: in the intermediate stretching regime (2.1 < 𝜆mac < 3.5), chains in low cross-linking regions begin to relax, while chains in highly cross-linked regions continue to function as load-bearing units.
This work was supported by the National Natural Science Foundation of China Excellent Young Scientists Fund (No. 52422302, Physics of Polymer Film Processing), and the Anhui Provincial Natural Science Foundation (No. 2308085UM02, Research on Principles and Key Processing Technologies for Highly Weather-Resistant Polarizers; No. 2408055UM001, Development of High-Performance Pressure-Sensitive Adhesives for Polarizers).
Lei Wu, Yuqi Xiong, Chengyan Li, Xiaojie Chen, Wei Chen*.Strain-Induced Accelerated Chain Dynamics in Cross-Linked Natural Rubber under Active Deformation: An in-situ Nuclear Magnetic Resonance Study [J]. Analytical Chemistry, 2025.
Paper Link：https://doi.org/10.1021/acs.analchem.5c01483
