Anomalous structure and scaling of ring polymer brushes

¹ Institut für Physik, Johannes Gutenberg-Universität - D-55099 Mainz, Staudinger Weg 7, Germany
² Institute of Physical Chemistry, Bulgarian Academy of Sciences - Sofia 1113, Bulgaria

^a reithd@uni-mainz.de

Received: 26 April 2011
Accepted: 25 May 2011

Abstract

A comparative simulation study of polymer brushes formed by grafting at a planar surface either flexible linear polymers (chain length N_L) or (non-catenated) ring polymers (chain length N_R=2N_L) is presented. Two distinct off-lattice models are studied, one by Monte Carlo methods, the other by molecular dynamics, using a fast implementation on graphics processing units (GPUs). It is shown that the monomer density profiles ρ(z) in the z-direction perpendicular to the surface for rings and linear chains are practically identical, ρ_R(2N_L,z)=ρ_L(N_L, z). The same applies to the pressure, exerted on a piston at height z, as well. While the gyration radii components of rings and chains in the z-direction coincide, too, and increase linearly with N_L, the transverse components differ, even with respect to their scaling properties: R_gxy^(L)∝N_L^1/2, R_gxy^(R)∝N_L^0.4. These properties are interpreted in terms of the statistical properties known for ring polymers in dense melts.