  Dendritic growth patterns exhibiting four-fold anisotropy are observed when
polyethylene oxide undergoes phase segregation from a solution phase to a solid
phase. When this phase transition occurs on a substrate that has patterns of
cross-linked polyethylene oxide resist pillars made using electron beam
lithography, the polymer grows in between the patterns giving rise to dendritic
growth structures exhibiting eight-fold anisotropy. This paper presents these
experimental observations and explains the dendritic growth using principles of
minimization of free energy associated with phase change. Numerical simulations
are carried out using phase-field modeling, and the results are shown to
qualitatively match experimental observations. The simulations reveal that the
polymer assumes the anisotropy of the patterned lattice.
