  Planar brushes of flexible, semiflexible and rodlike diblock polyampholytes
are studied using molecular dynamics simulations and scaling analysis in a wide
range of the grafting density. Simulations show linear dependence of the
average thickness on the grafting density for all the brushes regardless of
their different equilibrium conformations and different flexibility of anchored
chains. Slopes of fitted lines to the average thickness of the brushes of
semiflexible and rodlike polyampholytes versus the grafting density are
approximately the same and differ considerably from that of the brush of
flexible chains. The average thickness of the brush of diblock polyampholytes
is also obtained as a function of the grafting density using a simple scaling
analysis which is in good agreement with the results of our simulations.
