Molecular dynamics simulations of a poly(p‐phenylene) oligomer

We have studied the conformation and coefficient of thermal expansion in the poly( p ‐phenylene) oligomer p ‐sexiphenyl (C 36 H 26 ) by molecular dynamics simulations. Studies of the backbone phenyl–phenyl torsion angle in a simulated p ‐sexiphenyl crystal at room temperature indicate the presence of torsional librations of approximately ±20°. Further analysis of the phenyl–phenyl backbone torsion angle in less closely packed regions of the simulated crystal (crystal ends) indicate the presence of 180° phenyl ring flips, in agreement with solid‐state deuterium NMR data on poly( p ‐phenylene oligomers). The linear coefficient of thermal expansion was also calculated and found to be negative, in qualitative agreement with experimental data on rigid‐rod compounds.