The name is absent

nebulous and consequently, the density dependence of the thermodynamic functions is
often inadequate and can lead to the wrong conclusions about the nature of the phase
behavior. Broadly, continuum models include three approaches: extension of Flory-
Huggins theory in continuum space, integral equation theories, and theories based on
Wertheim’s first order thermodynamic perturbation theory (TPTl) [26, 27, 28, 29].
These theories are generally developed for hard chain fluids. In another step, attrac-
tive interactions can be added as a perturbation to the hard chain reference fluid.

Dickman and Hall [30] were the first one to develop an EOS for hard chain fluids
by extending the Flory-Huggins treatment of configurational probabilities of chain
molecules to continuous space. In this Generalized Flory (GF) theory, the probability
of inserting of a polymer chain into the system is approximated from the probability
of inserting a monomer (a single segment of the chain) into a fluid of monomers.
Comparisons with Monte Carlo simulation results show that the theory does not
yield accurate thermodynamic properties of chain fluids [31] as the effect of chain
connectivity is underestimated. Based on these conclusions, Honell and Hall [32]
developed an improved Generalized Flory-Dimer (GFD) theory. Now, the probability
of inserting the chain is obtained from the probabilities of inserting a monomer into
a monomer fluid and a dimer into a dimer fluid. GFD theory has been extended to
attractive [33] and heteronuclear [34, 35] chains.

Standard integral equation theories from statistical mechanics can be used to de-
termine the correlations between the segments forming the chains. This information

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