Molecular dynamics simulations of structural transitions of crystalline polystyrene in response to external stresses and temperatures

5 years ago

Molecular dynamics simulations of structural transitions of crystalline polystyrene in response to external stresses and temperatures

The structural transitions of syndiotactic polystyrene in response to external stresses and temperature were investigated in detail by molecular dynamics simulations. Upon uniaxial compression along the b-axis, the nanoporous ε form was transformed into a lower-density porous “S-I” form, accompanied by marked elongation of the a-axis. The S-I form was transformed into the γ form following stress reduction. The transition from the ε to the

β^{'}

form was also observed under tensile stress along the c-axis, which is associated with a conformational transition of the main chains. The stress responses and the reproducibility of the transitions were confirmed by extensive simulations. The thermal stability of the polymorphs was also examined via stepwise heating simulations. Experimentally observed thermal transitions of

ε \to γ

and

δ_{e} \to γ

were reproduced. It was found that the S-I form is more stable than the ε and

δ_{e}

forms under 0.27 GPa uniaxial stress along the b-axis. Considering the reproducibility of the stress-induced transitions and the thermal stability, the S-I form could be realized under an appropriate stress condition, though no experimental observation has been reported for now.

Publisher URL: www.sciencedirect.com/science

DOI: S003238611730890X