  Dynamics of Yamamoto-type poly(p-phenylene)[PPP] was investigated by
differential scanning calorimetry(DSC) and proton solid-state NMR relaxation
spectroscopy. The DSC chart shows the baseline jump without latent heat at
295K, which is due to the glass transition of the polymer. From the variable
temperature proton longitudinal relaxation time(T1) measurements, relatively
short T1 is observed over the wide temperatures range from 250K (closed to
Vogel-Fulcher-Tamman temperature) to 360K, inferred the existence of
cooperative critical slowing down associated withthe glass transition. The
frequency dependence of proton longitudinal relaxation time at 295K shows R1 ~
w^-0.5 dependence, which is due to the one-dimensional diffusion-like motion of
the backbone conformational modulation. The frequency dependence is held at
least up to 360K. From these experiments, we were able to observe the twist
glass transition of the backbone of PPP, of which critical dynamics has a
universality class of the three-dimensional XY model.
