  We present an application of Flory-type self-consistent field theory of the
flexible polymer chain dissolved in the binary mixture of solvents to
theoretical description of co-nonsolvency. We show that our theoretical
predictions are in good quantitative agreement with the recently published MD
simulation results for the conformational behavior of a Lennard-Jones flexible
chain in a binary mixture of the Lennard-Jones fluids. We show that our theory
is able to describe co-nonsolvency suppression through pressure enhancement to
extremely high values recently discovered in experiment and reproduced by full
atomistic MD simulations. Analysing a co-solvent concentration in internal
polymer volume at different pressure values, we speculate that this phenomenon
is caused by the suppression of the co-solvent preferential solvation of the
polymer backbone at rather high pressure imposed. We show that when the
co-solvent-induced coil-globule transition takes place, the entropy and the
enthalpy contributions to the solvation free energy abruptly decrease, while
the solvation free energy remains continuous.
