D. Rigby et al., COMPUTER-SIMULATIONS OF POLY(ETHYLENE OXIDE) - FORCE-FIELD, PVT DIAGRAM AND CYCLIZATION BEHAVIOR, Polymer international, 44(3), 1997, pp. 311-330
Parametrization of a force field capable of quantitatively describing
the gas, liquid and crystal phases of alcohols, ethers and polyethers
is described. Two applications are reported, the first employing atomi
stic simulations to study PVT (pressure, volume, temperature) and cohe
sive properties of oligomeric poly(ethylene oxide) (PEG) and related s
mall-molecule liquids, and the second to study the extent of ring form
ation in polymerization of poly(ethylene glycols) (PEGs) and hexamethy
lene diisocyanate (HDI). The atomistic simulations, focusing extensive
ly on liquids and amorphous poly(ethylene oxides), demonstrate the abi
lity to predict densities with an accuracy of 1%-2% over extended rang
es of at least 200K in temperature and 180 MPa in pressure. Densities
of related small-molecule liquids, dimethyl and diethyl ether and etha
nol at or close to saturation pressure are also well. reproduced to te
mperatures close to the critical temperature. Densities calculated for
methoxy-terminated oligomers are used to predict the density of melt
and amorphous high-molar-mass PEO with an accuracy of better than 1%.
Similarly, solubility parameters have been calculated as a function of
chain length for poly(ethylene glycol) oligomers and used effectively
to obtain estimates of the solubility parameter of high-molar-mass ma
terial. Additionally, crystal structures can also be well predicted. F
or the polymerization studies the Monte Carlo network simulation metho
d was modified to mimic diffusion of reactants during the polymerizati
on. Application to the PEG/HDI 'linear' polymerization system, using c
hain configurations generated with the atomistic force field, reveals
a major improvement in the ability of the method to predict the extent
of ring formation without adjustable parameters for polymerization co
nditions ranging from the bulk to highly dilute reaction conditions.