Microscopic mechanisms of crosslinked isoprene rubber deformation behavior and strain-induced crystallization study by atomic force microscopy

An understanding of the microscopic deformation behavior of crosslinked rubber is key to gaining insight into the mechanisms of the mechanical properties of rubber materials. In this study, we measured isoprene rubber (IR) under uniaxial tensile strain using atomic force microscopy (AFM) nanomechanical techniques to track the microscopic deformation of the IR rubber and to visualize the stress distribution at the nanoscale. The results showed that affine deformation, a classical theory in rubber deformation, did not occur at the microscopic scale, and interesting nanoscale heterogeneous deformation behavior was observed. Based on the AFM experimental results, we proposed a microscopic elongation behavior model that takes into account the heterogeneity of the crosslink density. In addition, we observed microcrystalline structures at the 10 nm scale at high strain, which is believed to be the first time that strain-induced crystallization (SIC) has been visualized in real space. The direct observation of SIC provides an important reference for the investigation of the self-reinforcing mechanisms of crystalline rubber. • Nanoscale stress distribution of stretched IR was visualized using AFM nanomechanics • SIC microcrystals (∼10 nm) were visualized in real space by AFM • Nonaffine, heterogeneous deformation was directly observed in crosslinked IR rubber • SIC forms a reinforcing network that enhances IR rubber strength at high-strain