  The aim of this paper is two-fold. First, via a phenomenological
consideration I show that, equally with the conventional phases (body-centred
cubic, hexagonal planar and lamellar), such non-conventional phases as simple
cubic, face-centered cubic, well known double gyroid as well as some other
phases could be stable in a vicinity of the critical point in the systems
undergoing the order-disorder and order-order transition. A general phase
diagram indicating the strength of so-called angle dependence of the forth
vertex necessary for existence of these non-conventional phases is presented.
Next, I demonstrate via a direct Leibler-like microscopic consideration of the
ternary ABC block and graft copolymers that these real systems do reveal these
nonconventional phases even close to the critical point. In particular, the
ternary ABC block copolymers with a long middle block non-selective with
respect to both side blocks are especially inclined to form the gyroid phase. A
new cubic non-centrosymmetric phase and some other cubic phases are also first
predicted to exist as the most stable low temperature phase instead of the
lamellar one. Such a phase behavior is suggested to be common for a new class
of materials we propose to call amphiphobic since their (macro)molecules
consist al least of three mutually incompatible types of monomers.
