  The generalized entropy theory (GET) offers many insights into how molecular
parameters influence polymer glass-formation. Given the fact that chain
rigidity often plays a critical role in understanding the glass-formation of
polymer materials, the GET was originally developed based on models of
semiflexible chains. Consequently, all previous calculations within the GET
considered polymers with some degree of chain rigidity. Motivated by unexpected
results from computer simulations of fully flexible polymer melts concerning
the dependence of thermodynamic and dynamic properties on the cohesive
interaction strength ($\epsilon$), the present paper employs the GET to explore
the influence of $\epsilon$ on glass-formation in models of polymer melts with
a vanishing bending rigidity, i.e., fully flexible polymer melts. In accord
with simulations, the GET for fully flexible polymer melts predicts that basic
dimensionless thermodynamic properties (such as the thermal expansion
coefficient and isothermal compressibility) are universal functions of the
temperature scaled by $\epsilon$ in the regime of low pressures. Similar
scaling behavior is also found for the configurational entropy density in the
GET for fully flexible polymer melts. Moreover, we find that the characteristic
temperatures of glass-formation increase linearly with $\epsilon$ and that the
fragility is independent of $\epsilon$ in fully flexible polymer melts,
predictions that are again consistent with simulations of glass-forming polymer
melts composed of fully flexible chains. Beyond an explanation of these general
trends observed in simulations, the GET for fully flexible polymer melts
predicts the presence of a positive residual configurational entropy at low
temperatures, indicating a return to Arrhenius relaxation in the low
temperature glassy state.
