  A theoretical study on the phase behaviors of a polymer solution confined
between two coaxial cylindrical walls is presented. For the case of a neutral
inner cylinder, the spinodal point derived through the Gaussian fluctuation
theory is confinement-independent because of the existence of a free dimension
in the system. The kinetic analysis indicates that the fluctuation modes always
have a component of a plane wave along the axial direction, which can lead to
the formation of a periodic-like concentration pattern. On the other hand, the
equilibrium structure of the system is obtained by using the self-consistent
mean-field theory (SCMFT) and the interplay between the "wetting" phenomenon
and the phase separation is observed by modifying the property of the inner
cylinderical wall.
