Role of Dynamic Asymmetry on the Collective Dynamics of Comblike Polymers: Insights from Neutron Spin-Echo Experiments and Coarse-Grained Molecular Dynamics Simulations

We investigate the collective dynamics of comblike polymers displaying nanosegregation in side groups and main-chain rich domains, where side groups and backbones are dynamically equivalent. Neutron spin-echo experiments on poly(alkylene oxide)s with increasing side-group length have been focused on the decay of inter- and intradomain correlations and are complemented with molecular dynamics simulations on a coarse-grained model. In general, a good qualitative agreement between simulation and experiment is found. The collective times at inter- and intradomain levels converge with decreasing temperature, implying a common glass transition, and separate at high temperatures, revealing an increasing role of connectivity. The features of collective relaxations—regarding stretching, characteristic time, and temperature dependence—are independent of branching. The standard stretching for side-group motions and the closeness of collective and self-motions show that the anomalies exhibited by dynamically asymmetric comblike macromolecules disappear