The dynamics of probe particles inside a polymer network

The diffusion of probe particles inside a polymer gel-like medium is a subject of great interest. Examples include protein diffusing through mucus membrane, nuclear pore complex or small molecules diffusing in polymer films and many more. We use coarse-grained molecular dynamics simulations to investigate the dynamics of the probe inside a polymer network made on a lattice representing a ordered polymer gel. Our study shows that the dynamics of the probe particle inside the polymer gel become increasingly subdiffusive with increasing probe size, network rigidity, and the probe-polymer affinity. Additionally, velocity autocorrelation functions have negative dips due to the viscoelastic nature of the gel. The van-Hove correlation function shows fat non-Gaussian tail for the sticky bigger probe particle as it locally stretches the network but the fat tail vanishes on increasing the rigidity of the network. Our simulation results are in qualitative agreement with a series of experiments on probe diffusion in polymer gel.