Influence of rigid side chain attraction on stiffness and conformations of comb copolymer brushes strongly adsorbed on a flat surface

The influence of side-chain attraction on the conformational properties of two-dimensional polymer brushes with rigid side chains is investigated using Monte Carlo simulations. Using a rigid backbone, a characteristic interaction strength is determined by investigating, the critical interaction energy for the collapse of. the side chains onto the backbone. For a flexible backbone, the persistence length of the backbone is found to decrease with increasing attraction, irrespective of whether side-chain flipping is allowed or not. This result is in good agreement with the theoretical modeling presented before. If side-chain flipping is allowed, the attraction between the side chains leads to aggregation of successive side chains at one side of the backbone resulting in a characteristic local spiraling of the backbone. Snapshots of polymer brushes consisting of a flexible backbone of 128 beads with every other bead carrying a rigid side chain of 8 beads pointing alternately to opposite directions of the backbone. Besides the excluded-volume interaction between all beads, the side-chain beads attract each other via a potential V(r) = -ε/r6 and the snapshots correspond to different values of β = ε/κT.