CONFORMATION AND MOBILITY OF 1,4-TRANS-POLYBUTADIENE IN THE CRYSTALLINE STATE

Simulations of the molecular dynamics of 1,4-trans-polybutadiene in the low- and high-temperature polymorphs (form I and form II, respectively) are compared with the simulation of the polymer as an inclusion complex in the channel of crystalline perhydrotriphenylene. The only internal motions of the dihedral angles in form I on the nanosecond time scale at 300 K are fluctuations of each dihedral angle about its mean value. The fluctuations in form I are smaller than the fluctuations in the other systems. At 360 K form II exhibits strongly correlated rotational isomeric state transitions of the type A +/- TA -/+ --> A -/+ TA +/-, where A denotes an anticlinal state at a CH-CH2 bond and T denotes a trans state at a CH = CH or CH2 - CH2 bond. The CH - CH2 bond is more mobile in the inclusion complex at 300 K than in form II at 360 K. The cis state is of negligible occurrence in form I, in form II, and in the inclusion complex, but it does occur as an important minor constituent at the CH - CH2 bonds in the isolated chain.