  Here we report the linear viscoelastic properties of amorphous
poly(tetramethylene oxide) (PTMO), which is one of the key components in
synthesizing segmented polyurethane (PU) elastomers. The temperature and
molecular weight dependent viscoelastic behavior is investigated in detail by
computing the shear relaxation modulus G(t) and the bulk relaxation modulus
K(t), using the Green-Kubo relationship with correlation function. Our results
provide new data for PTMO melt from the united atom model and also extend the
existing knowledge of viscoelastic properties of polymers in general. The
predicted viscoelastic behavior range is shifted on a master curve using the
time-temperature superposition principle (TTSP) with horizontal and vertical
shift factors. The emerging shift factors agree with the Williams-Landel-Ferry
(WLF) equation. For the validation of the united-atom model of PTMO using the
TraPPE-UA force field we explored the transport properties and observed a
position-dependent diffusion dynamics throughout the polymer chain, which
subsequently influences the scaling laws for chain dynamics. These findings are
discussed in terms of emerging experimental evidence on position dependent
displacement for different chain portions along the chain length.
