The Longitudinal Superdiffusive Motion of Block Copolymer in a Tight Nanopore

Authors:

• Waldemar Piotr Nowicki

Abstract

The structure and dynamic properties of polymer chains in a confined environment werestudied by means of the Monte Carlo method. The studied chains were represented by coarse-grainedmodels and embedded into a simple 3D cubic lattice. The chains stood for two-block linear copolymersof different energy of bead–bead interactions. Their behavior was studied in a nanotube formed byfour impenetrable surfaces. The long-time unidirectional motion of the chain in the tight nanoporewas found to be correlated with the orientation of both parts of the copolymer along the lengthof the nanopore. A possible mechanism of the anomalous diffusion was proposed on the basisof thermodynamics of the system, more precisely on the free energy barrier of the swapping ofpositions of both parts of the chain and the impulse of temporary forces induced by variation of thechain conformation. The mean bead and the mass center autocorrelation functions were examined.While the former function behaves classically, the latter indicates the period of time of superdiffusivemotion similar to the ballistic motion with the autocorrelation function scaling with the exponentt5/3.A distribution of periods of time of chain diffusion between swapping events was found and discussed.The influence of the nanotube width and the chain length on the polymer diffusivity was studied