Tunable Slow Dynamics of Three-Dimensional Polymer Melts through Architecture Engineering

Coarse-grained three-dimensional (3D) architectured polymers, namely, soft-clusters, exhibit a glassy yet melt state even at temperatures much higher than their glass transition temperature. In this study, we systematically modulated the number of beads and manipulated the 3D architectures of these soft-clusters. We unveiled the distinct decoupling of translational and rotational relaxation and identified three distinct types of viscoelasticity. Remarkably, the center-of-mass dynamics of soft-clusters are less sensitive to pressure and density, with the critical determinants being the compactness of the architecture and the number of beads, which collectively dictate a predefined level of cooperation. We established direct correlations between the divergent relaxation time, growth of dynamic heterogeneity, and the activation energy of the center of mass. Our findings underscore the essential role of predefined cooperativeness, introduced via chemical bonds (springs), in the behavior of soft-clusters. This novel realization of glassiness suggests a fruitful future for 3D-architectured polymers.