Hopping of Water in a Glassy Polymer Studied via Transition Path Sampling and Likelihood Maximization

Diffusion of small molecules in amorphous polymers is known to follow a form of so-called hopping motion: penetrant molecules are trapped in microscopic cavities for extended time periods; diffusion is made possible by rare but fast jumps between neighboring cavities. Existing understanding of the hopping mechanism is based on the inspection of molecular images during individual molecular-dynamics trajectories. We focus on the diffusion of …