Investigating the impact of strand length distribution on nonlinear relaxation in transient networks

In this study, a model transient network system, Tetra-PEG slime, was employed to elucidate the influence of heterogeneous strand length distribution on nonlinear stress relaxation behavior. Transient networks, characterized by their temporary crosslinks, are notable examples of viscoelastic liquids. Despite their widespread applications, the molecular mechanisms governing their viscoelastic responses under significant deformations remain unclear. The heterogeneous distribution of network strand lengths is particularly significant; however, controlling this parameter poses a considerable challenge owing to the limited availability of suitably designed experimental materials. Therefore, this study investigated the relationship between nonlinear stress relaxation and network strand distribution using model transient networks with controlled heterogeneous strand length distributions consisting of two size-mismatched tetra-armed precursors (bimodal Tetra-PEG slime). The strain at damping significantly decreased with the increasing degree of heterogeneity, which indicated that the strain energy per network strand decreased upon the introduction of heterogeneous strand length distributions. This behavior was attributed to stress concentration, which induced heterogeneous flow at an earlier stage and thereby triggered damping more readily. These insights provide a strong framework for understanding the complex rheological properties of transient networks. • Tetra-PEG slime model used to examine nonlinear stress relaxation behavior • Two-dimensional rheo-polarization imaging revealed spatially heterogeneous strain • Strand pullout contributed to damping in networks with varying strand lengths • Heterogeneous strand lengths reduced strain energy per strand during damping