Rather general mean field theory of heteropolymer liquids developed earlier reduces
the problem of the phase diagram construction to the determination of extremals
of the free energy functional. These should be subsequently analyzed for their
local and global stability. Tackling of this problem traditionally involves the examination
of the behavior of the solutions of a set of nonlinear algebraic and partial
differential equations at various values of the control parameters. Besides, the necessity
arises here to construct in space of these parameters the lines where a
polymer system loses the thermodynamic stability. To overcome mathematical difficulties
encountered we employed a complex approach that combines analytical
and numerical methods. A two-step procedure constitutes the essence of such an
approach. First, the bifurcation analysis is invoked to find the asymptotics of the
extremals in the vicinity of bifurcation points. Then these asymptotics are used as
an initial approximation for the numerical continuation of specific lines, where the
stability loss occurs, into regions of the parametric space far removed from bifurcation
values. We realized this approach for the melt of linear binary copolymers of
various chemical structure with macromolecules having a pattern of arrangement of
monomeric units describable by a Markov chain. Bifurcation and phase diagrams
for some of these copolymers have been constructed within a wide range of temperatures
and volume fractions of a polymer