  Polymer-related materials exhibit rich glassy behaviors at different length
scales due to their various molecular structures and topological constraints.
Recent studies have identified transient interpenetration of the long-chain
rings contributing to dynamic arrest on the center-of-mass level.
Interpenetration of rings is proposed as an approach to facilitate glass
formation in polymer melts. In this work, inspired by recent advances in the
synthesis of mechanically interlocked polymers, we investigate glass transition
on the nanometer-scale segments influenced by permanent interpenetration of
rings using molecular dynamics simulations. We find that decreasing chain
length in the mechanically interlocked system is equivalent to inducing an
effective chain stiffness on the sub-rings. The induced stiffness provides a
unified explanation for these unique structural features and transient dynamic
arrest in the system of interlocked rings with rather short chains. Further, a
crossover is observed in the scaling relation between localization and glassy
depth upon cooling. Our work reveals a dynamic transition from weak to strong
caging at the crossover temperature. According to the localization model, we
demonstrate that the chain stiffness increases the critical temperature and
oscillation distance, therefore leads to more fragile dynamics and deeper
glassy state. These findings are consistent with the predictions of molecular
simulations and theories for polymers with real local stiffness. Our work
deepens the understanding of the role of induced stiffness on glass transition,
and opens up a new direction to design rich glass materials by manipulating
stiffness through mechanical bonds.
