  To study the cooling behavior and the glass transition of polymer melts in
bulk and with free surfaces a coarse-grained weakly semi-flexible polymer model
is developed. Based on a standard bead spring model with purely repulsive
interactions an attractive potential between non-bonded monomers is added, such
that the pressure of polymer melts is tuned to zero. Additionally, the commonly
used bond bending potential [Everaers et al., Science 303, 823 (2004)]
controlling the chain stiffness is replaced by a new bond bending potential.
For this model, we show that the Kuhn length and the internal distances along
the chains in the melt only very weakly depend on temperature, just as for
typical experimental systems. The glass transition is observed by the
temperature dependency of the melt density and the characteristic non-Arrhenius
slowing down of the chain mobility. The model is set to allow for a fast switch
between models, for which a wealth of data already exists.
