Amorphous cis-1,4-polybutadiene P–V-T properties from atomistic simulations

Abstract

ContextThe experimental values of variation of glass transition temperature (Tg) with the pressure are relatively dispersed due to the diversity of microstructure encountered in Cis-1,4-Polybutadiene (PB) and the diversity of technics used for its measurement. Fortunately, atomistic simulations allow to get valuable information for very well controlled chemistry and structures using very well-de ned protocol of acquisition. That's why, atomistic modelling will be used to evaluate the variation of Tg with the pressure for a well-de ned amorphous oligomer of cis-1,4 PB. MethodAtomistic dilatometry was performed on model of amorphous cis-1,4 PB with a molecular weight of 5402 g.mol − 1 . The analysis was carried out by reporting with respect to the temperature, the speci c volume, the coe cient of thermal expansion, the total energy, and the constant volume heat capacity averaged over 7 independent con gurations. Tait equation was used to t the evolution of the speci c volume for temperatures between 10 K and 700 K and pressure of 0, 60 and 100 MPa. ResultsThe speci c volume evolution with temperature and pressure of the melt is predicted to be within 2% of error with the experimental values extrapolated for a similar molecular weight with a very well reproduced coe cient of thermal expansion. The best predictions of Tgs are obtained using the Tait equation t with a Tg predicted at 162 K at zero pressure and a linear dependence with pressure given a slope of 0.22 K/MPa. As recently observed for PEO and PS, the different calculated properties show hysteresis between the heating and cooling curves.