| Summary: | 博士 === 國立中山大學 === 化學學系 === 82 === Molecular dynamics (MD) simulation of a simple phenylene
polymer, poly(phenylene oxide) (PPO), was carried out with the
TRIPOS 5.2 force field. Two types of molecular motion were
examined: rotation of individual phenylene rings and torsion of
a large segment (i.e. four-oxygen segment, FOS) involving four
ether oxygen atoms and three phenylene rings. Model compounds,
diphenyl ether and 1,4-bis(4-phenoxy phenoxy) benzene, were
used to help the analysis of the result. Based on the
trajectory analysis, "in-phase" cooperative rotations of the
neighboring phenylene rings and "out-of-phase" cooperative
rotations of consecutive FOS''s, superimposed on random
segmental wiggles, were observed. Packing effect was found to
be important for the larger FOS rotations but not for the
rotation of individual rings. The diffusion coefficient for the
torsion of an FOS is about half of that for the rotation of an
individual phenylene ring, but remains within the same order-of-
magnitude. Another, the behavior of energy flow in a model
chain of amorphous polyethylene is discussed. The rate of
energy flow through the backbone of a polyethylene chain was
studied as functions of density, stretching force constant, and
temperature. It is found that the energy flow rate is fast
initially and becomes slower in later time. The dispersion of
excitation energy is found to be accelerated by the energy
transfer through nonbonded interactions. The rate of energy
flow is also sensitive to the stretching force constant and
temperature of the system.
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