Liquid Crystals are partially ordered system without a rigid, long
ranged structure, are beautiful and mysterious. In symmetry and
structure, they are intermediate between the solid crystalline state and
isotropic liquid state. The study of liquid crystalline materials covers
a wide area: chemical structure, physical properties and technical
applications. Due to their dual nature - anisotropic physical properties
of solids and rheological properties and easy response to external
perturbations (electric field, magnetic field etc.), liquid crystals are
of greatest potential of scientific and technological applications. The
subject of liquid crystal, in its experimental aspect, has come of age
and has achieved the status of being a very exciting interdisciplinary
field of scientific and industrial research. However, theoretical
understanding falls far behind and is awaited to answer many basic
questions. In the present monograph we addressed some of these problems
within the framework of Landau de Gennes formulation and by using the
unified molecular theory based on weighted density functional approach.