We have previously described an original model called the EVM
(energy, volume, and mass)
model, which uses only three descriptors, the energy of a polymer
segment conformation using molecular
mechanics and molecular dynamics, its volume (the occupied space by the
atoms as well the unoccupied
space between them), and the repeat unit molar mass, to calculate
successfully the glass transition
temperatures (T
g) of aliphatic acrylate and
methacrylate polymers. We report here the application
of
this model to a series of various polystyrenes. The EVM model
allows correct description of the substituent
position effect on the ring as well as on the backbone, for various
alkyl group and halides. The estimated
T
g values with the EVM model are in excellent
agreement with literature values. We compare this
model
with two other methods (Bicerano's model and Porter's approach) and
find better or comparable
correlations.