  The structural phase behavior of polymer brushes, single-component linear
homopolymers grafted onto a planar substrate, is studied using the molecular
Monte Carlo method in 3 dimensions. When simulation parameters of the system
are set in regions of macrophase separation of solution for the corresponding
non-grafted homopolymers, the grafted polymers also prefer segregation.
However, macrophase separation is disallowed due to the spatially-fixed
grafting points of the polymers. Such constraints on the grafting are similar
to connecting points between blocks of non-grafted diblock copolymers at the
microphase separation in the melt state. This results in "microphase
separation" of the homopolymer brush in the lateral direction of the substrate.
Here we extensively search the parameter space and reveal various lateral
domain patterns that are similar to those found in diblock copolymer melts at
microphase separation.
